Macrobrachium+malayanum

A webpage targeted at readers who wish to seek understanding of one component of tropical stream ecosystems/ macroinvertebrates **//Macrobrachium malayanum //**** (Roux, 1934) ** //A common freshwater shrimp in Singapore's natural freshwater habitats // Figures 1 & 2: Adult male //M. malayanum// (front and side view)
 * Photos by:** Claudia Tan

toc Freshwater shrimps of the //Macrobrachium// genus are probably more renowned for their value as food (the larger species such as //M. rosernbergii//), or less commonly, as pets. Species within this genus can be recognized by their **long, robust second chelipeds ** (pincers), which its name suggests (Greek; Macro = Big, Brachium = Arm). They are especially important in tropical freshwater habitats due to their sheer abundance and macroconsumer diet. Their distinct fighting behaviour and success in colonizing freshwater environments also have implications to their populations and diversification respectively. However, like any other Southeast Asian non-aquaculture shrimps, little investment has been made to understand its ecology.

In Singapore, there are a few //Macrobrachium// species in our fresh waters. The most abundant freshwater shrimp in the remnant forest streams is //M. malayanum// (Roux,1934) 1], which is also common in acidic forest streams in tropical Southeast Asia 2-5]. This freshwater shrimp can be identified by its having one pincer larger than the other (Figures 1-2), especially in mature males. Individuals can grow over 60 mm 6], or 20 mm in carapace length (CL) 7]. Similar to some species of the genus, their abundance in many tropical streams and their shredder-predator habits allows them to play a prominent role in ecosystem functioning 5, 8, 9].

Hence, this webpage is designed to:
 * 1) Touch upon the geographical distribution, habitats and distinguishing features of the species
 * 2) Introduce the ecological importance of freshwater shrimps like M. malayanum in tropical freshwater streams via its diet
 * 3) Increase understanding of interesting agonistic behaviour and how it affects its population
 * 4) Describe its adaptation in freshwater habitats from its life history strategies
 * 5)  Provide an overview of recent phylogenetic research of genus’ colonization into fresh waters

**Next Section:** Feeding and Ecological Role, Agonistic Behaviour, Life History Strategies, Shrimp Identification, Taxomony, Phylogeny

=** __<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">1) Geographic Distribution and Habitat __ ** = media type="custom" key="28069143" align="center" <span style="font-family: Verdana,Geneva,sans-serif;">Globally, //M. malayanum// is restricted to freshwater streams of tropical Southeast Asia, where it ranges as far up as Southern Thailand, to Malaysia, Sarawak and West Sumatra 2-4, 10, 11] (Figure 3). It is widespread in Singapore, common in the periphery and within forest streams of nature reserves and catchment areas 1, 4, 6, 7]. They are not known to occupy highly-artificial habitats like reservoirs, although they can be present in open rural-country streams 1].

<span style="font-family: Verdana,Geneva,sans-serif;"> <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 3: Global distribution of //M. malayanum// (Edited from Google Maps, 2015)

<span style="font-family: Verdana,Geneva,sans-serif;">//Macrobrachium malayanum// is a benthic (bottom-living) shrimp, and is thus often found amongst **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">leaf litter, between tree debris or roots/root mats **<span style="font-family: Verdana,Geneva,sans-serif;"> 4, 12]. It prefers clear, unpolluted streams 3, 4]. All habitats (Figure 4) are characterized by natural bottom sediment, including sand, rocks, and leaf beds 4].This species is restricted to **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">acidic forested streams **<span style="font-family: Verdana,Geneva,sans-serif;">, where pH can range from 4.90 to below 7.00 9, 13, 14]. The shrimp does not appear to be affected by canopy cover 7] or flow rate 4, 15], although its morphology could be influenced by flow velocity 4]. Furthermore, //M. malayanum// is **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">tolerant to low oxygen and calcium concentration **<span style="font-family: Verdana,Geneva,sans-serif;"> levels 16]. Such wide tolerance to different environmental parameters probably contributed to its wide distribution.

<span style="font-family: Verdana,Geneva,sans-serif;"> <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 4: One of forest stream habitats //M. malayanum// inhabits in Singapore <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">**Photo by:** Claudia Tan

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">**Previous Section:** Distribution and Habitat <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">**Next Section:** Agonistic Behaviour, Life History Strategies, Shrimp Identification, Taxomony, Phylogeny

=**__<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">2) Feeding and Ecological Role __**= media type="custom" key="28069137" align="center"

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">2.1 What does it eat?
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<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Videos 1-4 (Left to right, Top to bottom): //Macrobrachium// spp. (sold as Rusty macro) feeding on blood worms (Video Credit: YouTube user [|Dmytro Ko]); //M. meridionalis// feeding on detritus (Video Credit: YouTube user [|香港水生物愛護會/ 香港魚類愛護會]); //Macrobrachium// spp. (sold as Indian whisker shrimp) feeding on smaller glass/ghost shrimp (Video Credit: YouTube user [|Zach Dewey]); //Macrobrachium// spp. attacking conspecific that just molted (Video Credit: YouTube user [|Callatya])

<span style="font-family: Verdana,Geneva,sans-serif;">//Macrobrachium malayanum// is known to be **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">omnivorous **<span style="font-family: Verdana,Geneva,sans-serif;"> 9], feeding on **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">algae, detritus, leaf litter, and also on benthic macroinvertebrates **<span style="font-family: Verdana,Geneva,sans-serif;"> such as insect larvae/ nymphs, worms, snails and smaller shrimp 7] (See Videos 1-4 for an idea of the different food items //Macrobrachium// spp. can eat). It is, however, not known if this species is more carnivorous 17], or is it more omnivorous-detritivorous 18, 19].

<span style="font-family: Verdana,Geneva,sans-serif;"> <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 5: M. malayanum feeding on a forest halfbeak; **Photo credit:**Tan Heok Hui (permission obtained)

<span style="font-family: Verdana,Geneva,sans-serif;">The shrimp is also a **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">scavenger **<span style="font-family: Verdana,Geneva,sans-serif;">, and would attack and feed on **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">weakened or dead animals **<span style="font-family: Verdana,Geneva,sans-serif;"> like small fishes and other shrimps (e.g., in Video 3). A recent article has reported two //M. malayanum// individuals feeding on a forest halfbeak (//Hemirhamphodon pogonognathus//) approximately twice in size, probably when it was either weakened/ injured or cornered by the shrimps 20] (Figure 5). There have been shrimp hobbyists that have reported Macrobrachium species that attack and eat smaller fish as they grow bigger. They can also **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">cannibalize **<span style="font-family: Verdana,Geneva,sans-serif;"> on each other, especially when one has recently molted (pers. observ., Video 4).

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">2.2 What eats it?
<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 6: //M. malayanum// being eaten by an Oriental dwarf kingfisher. <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">**Photo credit:** Johnny Wee (permission obtained)

<span style="font-family: Verdana,Geneva,sans-serif;">There is no publication that has recorded the predators of //M. malayanum//. However, given that shrimps have been observed in the guts of fish, it can be assumed that some fish do prey on //M. malayanum//. Furthermore, birds are diurnal predators of the shrimp, as shown by a sighting of //M. malayanum// been fed on by an Oriental dwarf kingfisher (//Ceyx erithaca//)(Figure 5).

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">2.3 Key ecological role in the tropics


<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 7: Illustration of temperate freshwater food web, with ecological roles served by //M. malayanum// circled in blue. **Credit:** Federal Interagency Stream Restoration Working Group (1998), In: Stream Corridor Restoration: Principles, Processes, and Practices

<span style="font-family: Verdana,Geneva,sans-serif;">Tropical //Macrobrachium// freshwater shrimps are generalist ‘macroconsumers’— they facilitate **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">macro-decomposition by scavenging and shredding **<span style="font-family: Verdana,Geneva,sans-serif;">debris and leaf litter 21, 22]. They may also **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">regulate benthic macroinvertebrate **<span style="font-family: Verdana,Geneva,sans-serif;"> populations 23, 24]. In addition, they provide plentiful **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">food supply **<span style="font-family: Verdana,Geneva,sans-serif;"> for **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">larger ** <span style="font-family: Verdana,Geneva,sans-serif;">invertebrate and vertebrate **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">predators **<span style="font-family: Verdana,Geneva,sans-serif;">. They play multiple ecological roles served by various ‘specialist’ taxa in temperate inland waters 24, 25] (Figure 7). Combined with their high abundance 5], such roles can have significant impacts on ecosystem functioning, making them an important component in tropical stream ecosystems.

<span style="font-family: Arial,Helvetica,sans-serif;">Previous Section: Distribution and Habitat, Feeding and Ecological Role <span style="font-family: Arial,Helvetica,sans-serif;">Next Section: Life History Strategies, Shrimp Identification, Taxomony, Phylogeny

=**__<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">3) Agonistic Behaviour __**= media type="custom" key="28069177" align="center" <span style="font-family: Verdana,Geneva,sans-serif;">An interesting feature of the //Macrobrachium// genus is their agonistic behaviour (e.g, Video 5 shows a different //Macrobrachium// species fighting, Video 6 onwards shows //M. malayanum// individuals fighting), which is defined as any actions or behaviour related to fighting, inclusive of non-contact threat displays, chases and retreats. Agonistic behaviour is very distinctive in the //Macrobrachium// genus, probably due to their enlarged chela that they use in bouts. This distinctive behaviour also makes some of the more attractive or larger species of this genus interesting pets. However, this agonistic behaviour also limits aquaria hobbyists’ choices in keeping smaller pets or more than a handful of them at one time, which may explain their rare appearances in aquarium shops. This section will showcase content based on unpublished observations of //M. malayanum// agonistic interactions (as part of an ongoing research project), although discussion material and terminology (e.g., behavioural categories) are adapted from published behavioural studies on other //Macrobrachium// spp.

=media type="youtube" key="42Is0lpvEhw" height="299" width="489"= <span style="font-family: Tahoma,Geneva,sans-serif;">Video 5: //Macrobrachium formonense// individuals fighting (Video Credit: YouTube user [|香港水生物愛護會/ 香港魚類愛護會])

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">3.1 Characterization
<span style="font-family: Verdana,Geneva,sans-serif;">Agonistic interactions usually start the moment both individuals **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">detect/ investigate **<span style="font-family: Verdana,Geneva,sans-serif;"> one another, characterized by individuals turning towards/ approaching one another slowly, and/or antennules pointing in the direction of / touching one another (see Video 6, till 0:20).

media type="youtube" key="hf4rGosC4Dg" width="492" height="309" <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Video 6: Two //M. malayanum// individuals' first interaction in an experimental setting. Interaction escalates from investigating (0:00-0:20), threat display (0:20-0:40) to physical contact and bouts between two (0:40-0:46), ending when one retreats (at 00:46). <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">**Video credit:** Claudia Tan

<span style="font-family: Verdana,Geneva,sans-serif;">This is followed by **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">threat display **<span style="font-family: Verdana,Geneva,sans-serif;">, such an antennule whipping back and forth, lifting their chelipeds off the substrate and/ or in front of their opponent, charging, amongst a few others (see Additional Info for details of their agonistic behaviour; see Video 6 - 00:20-00:40, or Video 7 - 0:05-0:30 for an idea of their threat displays).

media type="youtube" key="KxePqvS8hPg" width="393" height="309" <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Video 7: Another pair of //M. malayanum// individuals' first interaction in an experimental setting, with a shorter investigation period than that in Video 6. Interaction escalates to threat display (00:05-00:30) to physical contact and bouts between two, ending when one retreats (at 00:55). Video credit: Claudia Tan

<span style="font-family: Verdana,Geneva,sans-serif;">The first interaction usually escalates to one involving **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">physical contact **<span style="font-family: Verdana,Geneva,sans-serif;"> (i.e. contact with chelae to determine the stronger individual. The <span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">duration and intensity of the interaction would vary according to the difference in dominance <span style="font-family: Verdana,Geneva,sans-serif;">between two individuals (e.g., in terms of size difference; compare Video 6, where both shrimps are similar in size, and Video 8, which features one distinctly larger shrimp and thus, **fight duration** was **shorter** than among the two similarly-size individuals in Video 6). After the first few interactions, <span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;"> fight intensity and duration usually decreases **<span style="font-family: Verdana,Geneva,sans-serif;">, **<span style="font-family: Verdana,Geneva,sans-serif;">as a dominance subordinate hierarchy would have been established.

media type="youtube" key="Niiius6BNd4" width="488" height="309" Video 8: Distinctly larger //M. malayanum// individual approaching and fighting with a smaller individual for shelter. Fight concluded within 22 seconds. **Video credit:** Claudia Tan

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">3.2 Winner gets priority access: Dominance Hierarchies
<span style="font-family: Verdana,Geneva,sans-serif;">Despite their agonistic behaviour, //<span style="font-family: Verdana,Geneva,sans-serif;">Macrobrachium //<span style="font-family: Verdana,Geneva,sans-serif;">species probably do not fight intensely all the time. Preliminary studies between //<span style="font-family: Verdana,Geneva,sans-serif;">M. malayanum //<span style="font-family: Verdana,Geneva,sans-serif;"> individuals show that fight intensity usually peaks in the first 10–20 minutes of contact, before a dominant-subordinate relationship is established.

media type="youtube" key="NSytND_fyiM" width="508" height="289" <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Video 9: Winner from video 8 defends its shelter effectively with just an attempted chela nip/ charge, ending the interaction quickly.

<span style="font-family: Verdana,Geneva,sans-serif;">Once the hierarchy is established, the **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">subordinate individual becomes submissive **<span style="font-family: Verdana,Geneva,sans-serif;">and acts distinctly differently from that of the dominant individual (Video 9; see Additional Info for more details of behaviour). Furthermore, subsequent interactions tend to involve **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">little or low-level physical contact **<span style="font-family: Verdana,Geneva,sans-serif;">(more threat displays or chases; chela push). <span style="font-family: Verdana,Geneva,sans-serif; line-height: 1.5;">Some level of physical contact can occur even after the first few interactions, but these are few relative to non-physical interactions and lower in intensity (e.g., chela push by dominant shrimp, or attempted chela nip).

<span style="font-family: Verdana,Geneva,sans-serif; line-height: 1.5;"> In general, fighting occurs for a longer time when the two shrimps are similarly-matched 26], be it in size, cheliped length/size/presence, molt stage, sex, or aggression levels. The more dominant the individual is, the less intense behaviour is required to elicit a submissive response by the subordinate 26, 27]. Such dominance hierarchies are also witnessed in other decapod crustaceans 28, 29].

3.3 Hierarchies minimize costs
<span style="font-family: Verdana,Geneva,sans-serif;">Agonistic behaviour plays a determining factor in attaining scarce resources, including refuges, food, and mates 30]. The establishment of dominance hierarchies may be a strategy to minimize costs in either individual 31].Fighting often involves energy expenditure on both individuals, and may sometimes lead to exhaustion, injuries, and death. Should the value of the contested resource be lower than the perceived cost of bouts, most animals, tend not to choose to initiate prolonged fights, especially if one individual is much more dominant over the other 26-28, 31]. However, fights still ensue to decide who can access the usually limited resource. A dominance hierarchy establishment thus allows access of resources of the stronger, dominant individual within a few bouts, and also reduces the potential injuries inflicted on the subordinate individual, at the expense of less preferable resource accessibility 31].

**3.4 Ecological consequences**
<span style="font-family: Verdana,Geneva,sans-serif;">Agonistic interactions would often **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">segregates dominant and subordinate individuals **<span style="font-family: Verdana,Geneva,sans-serif;">. Subordinate individuals tend to be forced into less preferable sites 32, 33], attain less optimal resources 30, 34], and thus may experience **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">slower growth, reproductive maturity or lower survival ** <span style="font-family: Verdana,Geneva,sans-serif;">as compared to dominant individuals 35, 36]. The extent varies from species to species, with some species being able to be kept at higher densities than others [e.g., 37, 38].

<span style="font-family: Verdana,Geneva,sans-serif;">One would thus expect that wild population densities would be kept low. This is not the case. Population studies reveal that many //Macrobrachium// spp., including //M. malayanum//, often reach high densities 14]. Behavioural observations in semi-natural conditions reveal that while aggressive interactions still take place over preferred resources and when a passing individual approaches within proximity of another, **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">fight intensity and frequency is not as high ** <span style="font-family: Verdana,Geneva,sans-serif;">as that observed in experimental and aquaculture conditions 32, 39]. This suggests a presence of a **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">strong dominance hierarchy in the wild **<span style="font-family: Verdana,Geneva,sans-serif;">, where social status is a key regulator of resource distribution.

<span style="font-family: Verdana,Geneva,sans-serif;">The cause for this stronger dominance hierarchy is not clear, although greater habitat/ shelter complexity in the wild could contribute to reduced resource competition with spatial segregation [e.g., 40]. This is seen in //M. rosernbergii// of varying molt stages, where individuals that are about to molt segregate themselves from the stronger inter-molt individuals, swimming towards the shallower, but more predator-susceptible waters 32]. Hence, while the effects of intraspecific agonism may not be as obvious in the wild, it probably __still affects__ the spatial distribution, and hence the vital survival and growth of dominant and subordinate individuals.


 * Previous Section: ** Distribution and Habitat, Feeding and Ecological Role, Agonistic Behaviour
 * Next Section:** Shrimp Identification, Taxomony, Phylogeny

=** __<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">4) Life History Strategies: Adaptations to freshwater life __ **= media type="custom" key="28069375" align="center"

4.1 Strategies
<span style="font-family: Verdana,Geneva,sans-serif;">Many species within the //Macrobrachium// genus are estuarine or amphidromous (i.e. juveniles live in brackish or marine waters, before migrating to fresh waters to spawn), producing a large number of small eggs. The lower investment per egg results in less developed, free-swimming larvae, requiring 10–13 larval stages stages before they develop to juveniles 41, 42]. Such may be __<span style="font-family: Verdana,Geneva,sans-serif;">disadvantageous in freshwater __<span style="font-family: Verdana,Geneva,sans-serif;">environments, which are characterized by as hypertonic 43], food-scarce 44, 45], torrential (in some areas) and prone to drying in the shallower or ephemeral streams 45]. There is also less need for large-scale dispersal as observed in oceanic crustaceans given the isolation of most freshwater habitats 41]. Hence, freshwater decapods, including //M. malayanum//, have developed a few life history strategies to enable it to thrive in such ‘harsh’ habitats. <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 8: Gravid //M. malayanum// (left) compared to a larger gravid (but dead) //M. nipponense// (right). Notice the difference in size (relative to mother's body length) and number of the eggs between the two species, //M. malayanum// being a wholly freshwater shrimp while //M. nipponense// being a brackish-water and freshwater species.
 * <span style="font-family: 'Chaparral Pro',serif; font-size: 12pt;">Main Strategy 1: Smaller Number of Eggs, but Larger in Size **
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Photos by: Claudia Tan **

<span style="font-family: Verdana,Geneva,sans-serif;">A general life history strategy adopted by freshwater animals is to produce less but larger eggs. Marine //Macrobrachium// spp. can **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">lay hundreds of thousands **<span style="font-family: Verdana,Geneva,sans-serif;"> of small eggs, while wholly freshwater shrimps like //M. malayanum// lay **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">as little as 26 eggs ** <span style="font-family: Verdana,Geneva,sans-serif;">(Table 1). While it is not known how many eggs //M. malayanum// produce, these eggs are considered large for the //Macrobrachium// genus, measuring 1.75–1.90 mm in length and 1.2–1.35 mm in diameter 42, 46], as **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">compared to < 1 mm in length and diameter of brackish-water shrimps ** <span style="font-family: Verdana,Geneva,sans-serif;">42] (Figure 8).

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Table 1: Comparison of life history strategies of selected //Macrobrachium// species. //Macrobrachium lar// and //M. niphanae// are not found in Singapore and are placed in the table due to the completeness of their data, allowing easier comparison. Citations beside species name refer to reference for life history data. Egg size refers to the volume of the eggs relative to the maximum carapace length of the ovigerous female.
 * **<span style="font-family: Verdana,Geneva,sans-serif;">Species ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Lifestyle ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Clutch Size ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Egg Size ** || <span style="font-family: Verdana,Geneva,sans-serif;">**Zoeal Stages** ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. lar// [[|47]] || <span style="font-family: Verdana,Geneva,sans-serif;">Sea water || <span style="font-family: Verdana,Geneva,sans-serif;">up to 40 000 || <span style="font-family: Verdana,Geneva,sans-serif;">Small || <span style="font-family: Verdana,Geneva,sans-serif;">11+ ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. equidens// [[|48]] || <span style="font-family: Verdana,Geneva,sans-serif;">Brackish water || <span style="font-family: Verdana,Geneva,sans-serif;">1000–6000 || <span style="font-family: Verdana,Geneva,sans-serif;">Small || <span style="font-family: Verdana,Geneva,sans-serif;">10 ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. nipponense// [[|49, 50]] || <span style="font-family: Verdana,Geneva,sans-serif;">Brackish water || <span style="font-family: Verdana,Geneva,sans-serif;">4700–5600 || <span style="font-family: Verdana,Geneva,sans-serif;">Small || <span style="font-family: Verdana,Geneva,sans-serif;">9 ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. nipponense// [[|50, 51]] || <span style="font-family: Verdana,Geneva,sans-serif;">Freshwater || <span style="font-family: Verdana,Geneva,sans-serif;">1129–2600 || <span style="font-family: Verdana,Geneva,sans-serif;">Small (but about 2 times larger than brackish water population) || <span style="font-family: Verdana,Geneva,sans-serif;">? ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. lanchesteri// [[|52]] || <span style="font-family: Verdana,Geneva,sans-serif;">Freshwater || <span style="font-family: Verdana,Geneva,sans-serif;">59–393 || <span style="font-family: Verdana,Geneva,sans-serif;">Medium || <span style="font-family: Verdana,Geneva,sans-serif;">2+ ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. malayanum// [[|46]] || <span style="font-family: Verdana,Geneva,sans-serif;">Freshwater || <span style="font-family: Verdana,Geneva,sans-serif;">? || <span style="font-family: Verdana,Geneva,sans-serif;">Large || <span style="font-family: Verdana,Geneva,sans-serif;">2 ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. sundaicum// [[|53]] || <span style="font-family: Verdana,Geneva,sans-serif;">Freshwater || <span style="font-family: Verdana,Geneva,sans-serif;">? || <span style="font-family: Verdana,Geneva,sans-serif;">Large || <span style="font-family: Verdana,Geneva,sans-serif;">2 ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">//M. niphanae// [[|54]] || <span style="font-family: Verdana,Geneva,sans-serif;">Freshwater || <span style="font-family: Verdana,Geneva,sans-serif;">32–81 || <span style="font-family: Verdana,Geneva,sans-serif;">Large || <span style="font-family: Verdana,Geneva,sans-serif;">2 ||

<span style="font-family: Verdana,Geneva,sans-serif;">Producing less but larger eggs **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">increases energetic investment to each egg **<span style="font-family: Verdana,Geneva,sans-serif;">, allowing for **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">more well-developed larvae **<span style="font-family: Verdana,Geneva,sans-serif;">. Marine crustacean larvae often lack functional organs/ appendages when just hatched, such as the mechanism to regulate osmo-ionic balance [[|44]]. This will be detrimental in their hypertonic environment. Freshwater shrimp larvae thus tend to have more developed organs to **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">cope with environmental stress **<span style="font-family: Verdana,Geneva,sans-serif;">.

<span style="font-family: Verdana,Geneva,sans-serif;">In addition, larvae of //M. malayanum// and other freshwater shrimps are **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">generally benthic **<span style="font-family: Verdana,Geneva,sans-serif;"> [[|46]] with **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">functional pereiopods **<span style="font-family: Verdana,Geneva,sans-serif;">(walking limbs) (Figure 8; see Figure 13 for illustration of shrimp body parts). In contrast, marine crustacean larvae are small and free-swimming. Such features would be dangerous for freshwater crustacean larvae, given the unpredictable flow speeds and abundance of predators in the freshwater realm [[|45]]. There is also no need for large dispersal within the usually isolated freshwater habitat [[|41]]. Thus, the functional pereiopods allow freshwater larvae to **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">hang onto substrate **<span style="font-family: Verdana,Geneva,sans-serif;"> [[|46]], seek optimal refuges and thus, have a higher chance of survival and development.

<span style="font-family: Verdana,Geneva,sans-serif;">Another life history strategy that //M. malayanum// has adopted to cope with a freshwater lifestyle is the reduction of larval phases and time, also known as abbreviated larval development. Similar to the first strategy, the abbreviation of larval development means that zoea from freshwater decapods are more well-developed when they hatch, including the presence of functional pereiopods and **<span style="color: #d6790c; font-family: Verdana,Geneva,sans-serif;">yolk reserves to undergo metamorphosis without the need to feed on external sources **<span style="font-family: Verdana,Geneva,sans-serif;"> [[|46], [|55]]. The shortening of larval development also **<span style="color: #d6790c; font-family: Verdana,Geneva,sans-serif;">reduces the time in which the larvae are vulnerable to predators and environmental conditions **<span style="font-family: Verdana,Geneva,sans-serif;">. Wholly freshwater shrimps such as //M. malayanum// tend to have about 2–3 zoea stages, as compared to > 10 stages in brackish water and marine //Macrobrachium// species (Table 1). They also spend less time in the phase (Figure 9).
 * <span style="font-family: 'Chaparral Pro',serif; font-size: 12pt;">Main Strategy 2: Abbreviated Larval development **

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;"> <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 9: Larval development of //M. malayanum// and some morphological changes through its development. Adapted from Chong & Khoo (1987).

<span style="font-family: Verdana,Geneva,sans-serif;">Ovigerous caridean (i.e. the superfamily //Macrobrachium// spp. belongs to) shrimps including //M. malayanum// **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">hold their eggs using pleopods **<span style="font-family: Verdana,Geneva,sans-serif;"> (Figure 9). Until they are ready to hatch, the mother **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">protects, grooms and aerates **<span style="font-family: Verdana,Geneva,sans-serif;">the eggs (Figure 10). This is in contrast to non-caridean shrimps that release their eggs immediately upon spawning. <span style="font-family: Verdana,Geneva,sans-serif;"> <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 10: Gravid //M. malayanum// female grooming eggs using her pereiopods. This involves her bending her body to reach the eggs. Re-adjustment of egg position and cleaning are usually done. Aeration is achieved by moving her pleopods up and down. **Photo by: Claudia Tan**
 * <span style="font-family: 'Chaparral Pro',serif; font-size: 12pt;">Parental care **

<span style="font-family: Verdana,Geneva,sans-serif;">Parental investment in egg production is also observed in the larval stages of //M. malayanum//, where **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">yolk reserves are still present in the larval stages **<span style="font-family: Verdana,Geneva,sans-serif;">[[|46]]. This allows them to attain nutrition while their feeding appendages are still developing [[|46]] while allowing them to tide over food-scarce conditions of freshwater environments better [[|56]].

<span style="font-family: Verdana,Geneva,sans-serif;">It is possible that blackwater or hillstream shrimps may have some extended parental care. This is illustrated by the ‘//M. hendersoni// complex’ (**NOTE:** //M. malayanum// is not part of this complex), where the mother continues to protect the larvae for a few days after hatching without feeding [[|57]].

4.2 Relation to freshwater colonization in genus
<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 11: Illustration of the evolution of life history traits in Asian //Macrobrachium//. Bold (blue) branches are lineages with strict freshwater lifestyle derived from preferred optimization from. Relative egg size and numbers are mapped above branches. Figure taken from Worwor et al. (2009)/ Molecular Phylogenetics and Evolution 52: 340–350; with **permission from corresponding author**. Permission pending from publisher.

<span style="font-family: Verdana,Geneva,sans-serif;">Some research have suggested that the //Macrobrachium// genus derived from a marine ancestor, which then diverged and colonized freshwater habitats (see Phylogeny for details). What makes it more intriguing is that **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">life history traits **<span style="font-family: Verdana,Geneva,sans-serif;"> like abbreviated larval development and large-intermediate egg size are characters found to be **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">significantly correlated with freshwater life cycles **<span style="font-family: Verdana,Geneva,sans-serif;"> [[|42], [|58]], making it possible that these traits may be used as a proxy to determine the evolution of the genus.

<span style="font-family: Verdana,Geneva,sans-serif;">Unfortunately, these traits were likely to be gained by different freshwater shrimp clades independently [Figure 10, [|58]], even within the geographical location. One example to illustrate this would be between //M. platycheles// and //M. malayanum//, both of which can be found in Singapore. Although these two species are wholly freshwater species with abbreviated larval development, large egg size, and with overlapping distributions and populations, they do not share a common ancestry [[|42], [|60]]. This thus supports the hypothesis that more than one wave of freshwater invasion by //Macrobrachium// spp. occurred within the Southeast Asian region. These set of life history traits in different 'clades' of //Macrobrachium// spp. could thus be a phenomena of **adaptive convergence** [[|42], [|58-60]].


 * Previous Section:** Distribution and Habitat, Feeding and Ecological Role, Agonistic Behaviour, Life History Strategies
 * Next Section:** Taxomony, Phylogeny

=**__<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">5) Diagnosis: Which shrimp is which? __**= <span style="font-family: Verdana,Geneva,sans-serif;">Shrimps from the //<span style="font-family: Verdana,Geneva,sans-serif;">Macrobrachium //<span style="font-family: Verdana,Geneva,sans-serif;"> genus are the most ubiquitous decapod in many Southeast Asian tropical freshwater streams. However, they can be very similar in appearance. //Macrobrachium malayanum// can be identified by its **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;"> hairy and robust main cheliped **<span style="font-family: Verdana,Geneva,sans-serif;"> in **mature** **males**, **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">conical carpus **<span style="font-family: Verdana,Geneva,sans-serif;"> and generally **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">short rostrum **<span style="font-family: Verdana,Geneva,sans-serif;"> (see Figure 13 for shrimp anatomy illustration). However, there are morphologically-similar species in Singapore that co-occur with it, such as the critically endangered //M. platycheles//. Other species that one may encounter together with //M. malayanum// are //M. sundaicum// and introduced //M. nipponense// (Figure 12), and identification can be challenging due to their similar (or variable) colouration.

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 12: Freshwater //Macrobrachium// spp. with populations sympatric with //M. malayanum//: **A)** //M. malayanum;// **B):** //M. platycheles//; **<span style="font-family: Verdana,Geneva,sans-serif; font-size: 11.7px;">C): **<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">//M. sundaicum.// **Photos credit: Kenny Chua**, (permission obtained); **D)** //<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%; line-height: 1.5;">M. nipponense //<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%; line-height: 1.5;"> ( **<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%; line-height: 1.5;">Photo by: Claudia Tan) **

<span style="font-family: Verdana,Geneva,sans-serif;">Distinguishing freshwater shrimps could help in identifying a common from a threatened native species, or a native from an introduced species. Furthermore, as mentioned earlier, different species may play varying ecological roles depending on their diets and feeding rates, something that is still not known in Singapore's shrimp populations. Identification would thus help increase understanding in species-specific ecology.

<span style="font-family: Verdana,Geneva,sans-serif;">This section would thus cover the general morphological features between these species (Table 3). Please note that distinguishing them in the field can be a challenge, especially if they are not yet mature adults and thus, their chela and rostrum are not yet fully developed/well-defined. In the //Macrobrachium genus//, the main body parts that are key distinguishing features are their **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">pincers **<span style="font-family: Verdana,Geneva,sans-serif;"> (second pereiopods/ chelipeds) and their **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">rostrum shape **<span style="font-family: Verdana,Geneva,sans-serif;"> (see Figure 13 for anatomy illustration). Colouration is also not a good indicator, although patterns may ease identification when present on the individual. Identification could require some technical knowledge, thus readers are suggested to look at the illustrated diagram of a shrimp’s body parts (Figure 13) and an example of some distinguishing morphology on //Macrobrachium// spp. (Figure 14) before proceeding. <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 13: Illustration of shrimp body parts using //M. malayanum// photographs. Photo above captures a juvenile //M. malayanum,// hence its chelae are not yet as well-developed. Bottom photo shows the pleopods better since the shrimp is in water. Please note that colouration of this species ranges from pale yellow/brown to reddish-brown, and even black. **Photos by: Claudia Tan**

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;"> <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 14: A) Headshot of //M. nipponense// and labels to depict distinguishing features of species. B) Headshot of //M. malayanum// with labels to depict distinguishing features of species and photo of individual submerged in water (to show hairs on chela).
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Photos by: Claudia Tan **

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Table 3: Comparison of selected Singapore //Macrobrachium// species morphology. CL in 'max. size' row refers to carapace length, which is a more consistent way of measuring live shrimps in the field. > than palm
 * || [[image:M_malayanum.jpg width="223" height="171" align="center"]] || [[image:M_platycheles.jpg width="206" height="170" align="center"]] || [[image:M_sundaicum.jpg width="227" height="159" align="center"]] || [[image:M_nipponense.jpg width="231" height="161" align="center"]] ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Species ** || <span style="display: block; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; text-align: center;">**//M. malayanum//** || <span style="display: block; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; text-align: center;">**//M. platycheles//** <span style="display: block; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; text-align: center;">(critically-endangered) || <span style="display: block; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; text-align: center;">**//M. sundaicum//** || <span style="display: block; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; text-align: center;">**//M. nipponense//** <span style="display: block; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; text-align: center;">(introduced) ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Sympatric at? ** || <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">- || <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Nee Soon Swamp forest stream || <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">In most of //M. malayanum// local distribution, albeit in smaller numbers || <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Forest stream-reservoir interfaces (e.g., Lorong Banir stream) ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Max. Size (males) ** || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">CL: 20 mm, <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">although it can grow larger (pers oberv.) || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">CL: 9.8 mm || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">CL: 21 mm || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">CL: 27 mm, <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">largest in reservoirs ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Colour/ Pattern ** || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Ranges from orange-brown/ red-brown, brown to dark red and even black;
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">No stripes or bands on body || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Mottled grey/ brown with <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">brown or black bands || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">__May__ have dark brown/ grey/ black stripes on body;
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Colouration similar to //M. malayanum// || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">More translucent than the rest, larger individuals may also be greyish ||
 * || **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Cheliped/Second Pereiopod ** ||  ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Shape ** || * **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Carpus conical **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">; __shorter__ than merus
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Fingers __shorter__ than palm
 * **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Major chelipeds of adult males are very unequal **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">, sub-equal in females and juveniles || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Carpus **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">conical **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">; __much shorter__ than merus
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Fingers __shorter__ than palm
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Major chelipeds **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">sub-equal ** <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">in males and females
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Chelipeds laterally **flattened and very broad** || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Carpus **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">cylindrical **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">; __length equal/ longer__ than merus
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Fingers __subequal/ longer__
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Major chelipeds **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">sub-equal **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> in males and females || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Carpus **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">cylindrical **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">; __length equal/ longer__ than merus
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Fingers __subequal/ longer__ than palm
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Major chelipeds **<span style="color: #db7700; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">sub-equal ** in males and females
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Larger adults have L-shaped chelipeds ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Hairs/ Spines ** || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Stiff setae scattered on minor second periopod
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Mature males may have **<span style="color: #159400; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">dense velvety hairs **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> on almost entire chela || * **<span style="color: #159400; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Dense velvety hairs **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;"> on almost entire chela in mature adults || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;"> Stiff setae scattered on whole cheliped on **both** second pereiopods
 * **<span style="color: #159400; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">No **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> dense velvet hairs || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Stiff setae scattered on whole cheliped on **both** second pereiopods
 * **<span style="color: #159400; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">No **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> dense velvet hairs ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Pattern ** || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">May have **<span style="color: #002dcf; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">reddish bands at joints **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> of pereiopods
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Finger tips tend to be white || <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">- || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">May have **<span style="color: #002dcf; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">brownish/ black bands **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> at joints of pereiopods
 * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Finger tips tend to be white || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">May have **<span style="color: #002dcf; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">yellowish/ pale yellow bands **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;"> at joints of pereiopods ||
 * || **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Rostrum ** ||  ||   ||   ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;"> Shape ** || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Straight or slightly convex || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Straight || * **<span style="color: #8915b3; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Very concave **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;"> (curves upwards) || * <span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Straight, blade-like or slightly convex ||
 * **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Relative length ** || * **<span style="color: #d10c76; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Short **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">; not extending beyond antennular peduncle (AP) || * **<span style="color: #d10c76; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Short **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">; not extending beyond AP || * **<span style="color: #d10c76; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Extends to or slightly beyond **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;"> antennular peduncle || * **<span style="color: #d10c76; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">Extends to or slightly beyond **<span style="font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif; line-height: 1.5;">antennular peduncle ||


 * Previous Section:** Distribution and Habitat, Feeding and Ecological Role, Agonistic Behaviour, Life History Strategies, Shrimp Identification
 * Next Section:** Phylogeny

=**__<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">6) Taxonomy __**=

6.1 What’s in the name?
<span style="font-family: Verdana,Geneva,sans-serif;">**Scientific name:** //Macrobrachium malayanum// (Roux, 1934)

<span style="font-family: Verdana,Geneva,sans-serif;">“Malayan freshwater shrimp” and “Malayan river prawn” have been seen in literature, albeit infrequently. Such names may also be confused with the Malaysian giant prawn/ Giant freshwater prawn/ Giant river prawn, which is a different species, //Macrobrachium rosernbergii//, a famous large shrimp often harvested in aquaculture (but also sometimes seen in aquarium trade).
 * <span style="font-family: Verdana,Geneva,sans-serif;">Common names: **


 * <span style="font-family: Verdana,Geneva,sans-serif;">Junior Synonyms: **
 * <span style="font-family: Verdana,Geneva,sans-serif;">//Palaemon (Macrobrachium) pilimanus malayanus// (Roux, 1934)
 * <span style="font-family: Verdana,Geneva,sans-serif;">//Macrobrachium geron// (Holthuis, 1950)
 * <span style="font-family: Verdana,Geneva,sans-serif;">//Macrobrachium pilimanus// (Holthuis, 1950)
 * <span style="font-family: Verdana,Geneva,sans-serif;">//Cryphiops geron// (Johnson, 1966)

<span style="font-family: Verdana,Geneva,sans-serif;">//Macrobrachium malayanum// was first described by Roux 11], whom identified the shrimp as a new sub-species of //Palaemon (Macrobrachium) pilimanus// due to their similar length and overlapping geographical distribution 11, Figure 15]. //Macrobrachium pilimanus// is known for its variable morphology and many sub-species have been grouped under the //M. pilimanus// complex 11]. The terms “malayanus” and “malayanum” were probably to refer to the species’ locality within Peninsula Malaysia, similar to other species such as //Helarctos malaynus// (Malayan sun bear).
 * <span style="font-family: Verdana,Geneva,sans-serif;">Etymology: How did it get its name? **

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 15: Original description of //M. malayanum// (Roux, 1934). Original description available online at the [|Bulletin of the Raffles Museum Archives, Vol. 9]

<span style="font-family: Verdana,Geneva,sans-serif;">Holthuis (1950) collected a single adult male specimen and identified it as a new species, //M. geron//. The name geron is based on a Greek word that means “greyhead”, due to the long grey hairs on the major cheliped and the maturity of the specimen 10]. However, the use of only one specimen for species identifcation was erroneous. Later, Chong & Khoo (1987) synonymized //M. pilimanus malayanus// with //M. geron// after determining them as identical specimens. The authors also note that the species is markedly different from //M. pilimanus// (De Man, 1879), thereby promoting it to a full species status as //M. malayanum// (Roux, 1934).

6.2 Type Information
<span style="font-family: Verdana,Geneva,sans-serif;">Type locality: Lasah, Plus Valley, East Perak, Malaysia <span style="font-family: Verdana,Geneva,sans-serif;">Type: Lectotype <span style="font-family: Verdana,Geneva,sans-serif;">Depository: Basel Museum of Natural History, Switzerland <span style="font-family: Verdana,Geneva,sans-serif;">Label: NHMB 711.Ia.i

<span style="font-family: Verdana,Geneva,sans-serif;">Amongst the original collection of Tweedie, M.W.F. in 1933, one specimen from the first described collection was subsequently selected by Roux to serve as the single type specimen (lectotype). The specimen was the largest and most intact male in the collection, measuring 9.5 mm in carapace length 11].The remaining specimens among the set of syntypes (the original described collection of multiple individual of the species) are called paralectotypes (Table 2).

<span style="font-family: Verdana,Geneva,sans-serif;">Table 2: Paralectotype information of //Macrobrachium malayanum// 4]
 * **<span style="font-family: Verdana,Geneva,sans-serif;">Year of collection ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Number and sex of type specimens ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Type Locality ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Depository ** || **<span style="font-family: Verdana,Geneva,sans-serif;">Label ** ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">1933 || * <span style="font-family: Verdana,Geneva,sans-serif;">4 males, 13 females || <span style="font-family: Verdana,Geneva,sans-serif;">Lasah, Plus Valley, East Perak, Malay Peninsula || <span style="font-family: Verdana,Geneva,sans-serif;">Basel Museum of Natural History, Switzerland || <span style="font-family: Verdana,Geneva,sans-serif;">NHMB 711.Iaii ||
 * <span style="font-family: Verdana,Geneva,sans-serif;">1971 || * <span style="font-family: Verdana,Geneva,sans-serif;">10 males, 10 females, 15 juveniles ||^  || <span style="font-family: Verdana,Geneva,sans-serif;">Zoological Reference Collection, Singapore || <span style="font-family: Verdana,Geneva,sans-serif;">ZRC no. 1971.3.5.1–35 ||


 * Previous Section: ** Distribution and Habitat, Feeding and Ecological Role, Agonistic Behaviour, Life History Strategies, Shrimp Identification, Taxomony

=**__<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">7) Phylogeny __**= media type="custom" key="28069379" align="center"

7.1 Some relationships in Family Palaemonidae still unresolved
<span style="font-family: Verdana,Geneva,sans-serif;">Before going in the phylogenetic relationships of the //Macrobrachium// genus, readers should take note that the phylogeny of the family which //Macrobrachium// belongs in, Palaemonidae Rafinesque, 1815, has yet to be resolved. Recent research findings have provided strong evidence of the collapse of the family Kakadcarididae Bruce, 1993 with the Palaemonidae, further enlarging the family 61, 62]. Despite this, Palaemonidae are still considered paraphyletic 63, 64], with families such as Hymenoceridae Ortmann, 1890 been nested within the family (Figure 16), and could be synonymised within Palaemonidae 64]. The systematic relationship between families Anchistiodidae and Palaemonidae is also still unresolved 63, 64]. Hence, the systematic relationship of the Palaemonidae may be subjected to changes in the future 63, 64].

<span style="font-family: Verdana,Geneva,sans-serif;">

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Figure 16: Derived cladogram of family relationships hypothesized within the Palaemonoidea ‘superfamily’ taxa using molecular analyses. Stronger evidence is indicated using thicker lines.Figure taken from De Grave et al. (2015)/ PeerJ 3: e1167. Article is distributed under the Creative Commons Attribution License.

7.2 Genus name could be changed?
<span style="font-family: Verdana,Geneva,sans-serif;">Furthermore, even within the sub-family of Palaemoninae, re-assessment of a few genera, including //Macrobrachium//, is likely. An old confusion would be between the species-rich genus //Palaemon// and //Macrobrachium//. Many species in the current //Macrobrachium// genus was initially placed under the genus, //Palaemon// Weber, 1795, including //M. malayanum// (one of the junior synonyms is //Palaemon pillimanus malayanus// from the first descriptor of the species, Roux (1934)). Some species of //Macrobrachium// have also been found to be closer to the //Palaemon// genus, e.g., //M. intermedium// 60]. There could thus be further shifts between these genera as molecular data becomes more available to validate interspecific and intergeneric morphological comparisons, vice versa.

<span style="font-family: Verdana,Geneva,sans-serif;">To add to the confusion, there is a possibility of mergers between some genera and //Macrobrachium// 63]. One of which is between the genus //Cryphiops// Dana, 1852 and //Macrobrachium// Spence Bate, 1868 63, 65]. The close morphological similarity between the two genera has made identification through morphology insufficient to some, with many species been placed and transferred between the two genera, including //M. malayanum// (i.e. //Cryphiops geron// by Johnson (1966)). If so, the genus would be re-named as the senior genus, //Cryphiops// 63]. Such issues may result in future changes of the Palaemondidae family and even the //Macrobrachium// genus with sufficient and reproducible molecular evidence.

7.3 Evolution within genus
<span style="font-family: Verdana,Geneva,sans-serif;">The genus //Macrobrachium// is the most speciose in the family Palaemonidae, and one of the most diverse and widely-distributed crustacean genera 60]. This **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">wide geographical distribution and great diversity of habitats **<span style="font-family: Verdana,Geneva,sans-serif;">it has colonized has garnered interest of the biogeographical and evolutionary relationships of this group. This is especially so given that the variety of life cycles and life history traits seem to be associated with their respective habitats, making one wonder if there is any evolutionary or phylogenetic significance behind these traits 42, 55, 60, see Section 4.2]. Furthermore, despite their widespread distribution, there seems to be a high degree of morphological similarity between species 10], challenging traditional taxonomic work. It is thus hoped that molecular and phylogenetic data could reinforce traditional morphological data in species identification. In particular, an increasing interest has been diverted to the //Macrobrachium// species in Asia 42, 58]. This is due to the bulk of //Macrobrachium// diversity occurring in the region (and in the Indian subcontinent) 66], commercial importance of some species 66] and their key ecological component in these habitats 5].

<span style="font-family: Verdana,Geneva,sans-serif;">Some studies have thus been conducted to understand the phylogenetic relationships of the genus in relation to their geographical distribution, lineage and life history traits. Various molecular markers, including genes from mitochondrial and nuclear genomes were used. Some progress has been made in this field, although findings still remain contentious or incomplete. Below are a summary of the findings made thus far:

<span style="font-family: Verdana,Geneva,sans-serif;">**(1) //Macrobrachium// could be an old lineage** 60] <span style="font-family: Verdana,Geneva,sans-serif;">The large genetic divergence amongst species, even with the use of a highly conserved mtDNA sequence 16S rRnA, indicates that there was a significant time period for speciation to take place. A large portion of //Macrobrachium// fauna may have originated as far back as the **<span style="color: #d97316; font-family: Verdana,Geneva,sans-serif;">late Oligocoene/ early Miocene, i.e. 20–30 million years ago **<span style="font-family: Verdana,Geneva,sans-serif;">, and diversified earlier in their evolutionary history rather than recently. Unfortunately, the lack of fossil records of the //Macrobrachium// genus has made it a challenge to give a more accurate age of the genus.

<span style="font-family: Verdana,Geneva,sans-serif;">//Macrobrachium// is likely to have derived from a widespread marine ancestor that subsequently migrated towards freshwater habitats in multiple waves of migration 42, 58, 67]. This would explain the more widespread distribution of marine and estuarine //Macrobrachium// species, which would have the ability to overcome marine barriers in migration, before evolving and specializing in the more land-locked freshwater habitats across the subtropics and tropics. However, there are also studies that concluded that the genus is originally from a freshwater environment, before radiating to estuarine/marine habitats 60]. Thus, the ancestry of //Macrobrachium// is still in dispute.
 * <span style="font-family: Verdana,Geneva,sans-serif;">(2) Macrobrachium probably derived from a marine ancestor <span style="color: #c40505; font-family: Verdana,Geneva,sans-serif;"> (contentious) **

<span style="font-family: Verdana,Geneva,sans-serif;">There is little support for major endemic radiations, i.e. many sympatric species are not within the same sister group 60, 68, 69]. One local example would be the high genetic divergence between //M. malayanum// and //M. playtycheles//, which are both found in Singapore, Nee Soon Swamp, suggesting that they not derive from a single wave of ancestral migration and are not closely-related despite their overlapping distributions 60]
 * <span style="font-family: Verdana,Geneva,sans-serif;">(3) Macrobrachium have weak biogeographical patterns **

<span style="font-family: Verdana,Geneva,sans-serif;">There may however been some influence of the Wallace’s Line on delineation, as demonstrated by the large genetic divergence between Eastern and Western populations of the widely distributed //M. rosernbergii// 60, 70]. This finding supports the following:
 * <span style="font-family: Verdana,Geneva,sans-serif;">Several waves of migration into fresh waters occurred within the genus
 * <span style="font-family: Verdana,Geneva,sans-serif;">The ancestor of //Macrobrachium// was probably marine, as oceanic biogeographical barriers did not affect its dispersal capacity
 * <span style="font-family: Verdana,Geneva,sans-serif;">The lineage of //Macrobrachium// predates at least 10 million years ago, before the collision of the Sunda and Sahul tectonic plates, hence explaining the wide distribution and regional non-monophyly in the Indo-West Pacific //Macrobrachium// species

=** __<span style="font-family: 'Chaparral Pro',serif; font-size: 14pt;">Additional Info on Agonistic Behaviour __ **= = = <span style="font-family: Verdana,Geneva,sans-serif;">
 * <span style="font-family: 'Chaparral Pro',serif; font-size: 12pt;">Behaviour Characterization **

<span style="font-family: Verdana,Geneva,sans-serif;">After a dominance hierarchy is established, bouts rarely emerge. Detection of another individual after hierarchy formation usually results in either:
 * <span style="font-family: 'Chaparral Pro',serif; font-size: 12pt;">Dominant-Subordinate Behaviour Differences **
 * 1) <span style="font-family: Verdana,Geneva,sans-serif;">A quick retreat by the subordinate shrimp as the dominant shrimp approaches, and the dominant shrimp does not pursue it
 * 2) <span style="font-family: Verdana,Geneva,sans-serif;">Threat displays like charging by dominant shrimp and resultant retreat by the subordinate shrimp

<span style="font-family: Verdana,Geneva,sans-serif;">Once the hierarchy is established (Video 9 and 10), the subordinate individual becomes submissive and acts differently from that of the dominant individual. With regard to //M. malayanum//, these are some of the differences in behaviour:

<span style="font-family: Verdana,Geneva,sans-serif;">Dominant individuals tend to:
 * **<span style="color: #b52218; font-family: Verdana,Geneva,sans-serif;">patrol around the bottom **<span style="font-family: Verdana,Geneva,sans-serif;"> of experimental tank more regularly if there is no shelter present (Note: //M. malayanum// is a benthic species)
 * **<span style="color: #081dde; font-family: Verdana,Geneva,sans-serif;">occupy or defend a shelter **<span style="font-family: Verdana,Geneva,sans-serif;"> (if any)/ fixed area (e.g., Video 9), and
 * <span style="font-family: Verdana,Geneva,sans-serif;">initiate **<span style="color: #04a628; font-family: Verdana,Geneva,sans-serif;">chases or attempted chela push/nips **<span style="font-family: Verdana,Geneva,sans-serif;"> on the subordinate (Video 10)

<span style="font-family: Verdana,Geneva,sans-serif;">Subordinate individuals tend to:
 * **<span style="color: #b52218; font-family: Verdana,Geneva,sans-serif;">swim to the surface **<span style="font-family: Verdana,Geneva,sans-serif;"> and rest of the surfaces of the tank, swimming down at times and either 1) <span style="color: #b52218; font-family: Verdana,Geneva,sans-serif;">restrict themselves to an area where the dominant individual less frequents <span style="font-family: Verdana,Geneva,sans-serif;">, or 2) swims back up when it encounters and gets chased by the dominant individual (Video 10)
 * <span style="font-family: Verdana,Geneva,sans-serif;">stays **<span style="color: #081dde; font-family: Verdana,Geneva,sans-serif;">outside of shelter **<span style="font-family: Verdana,Geneva,sans-serif;"> (although some individuals make failed attempts to enter shelter, e.g., Video 9)
 * **<span style="color: #04a628; font-family: Verdana,Geneva,sans-serif;">retreats **<span style="font-family: Verdana,Geneva,sans-serif;"> almost immediately and does not initiate a fight with the dominant individual (Video 10)

media type="youtube" key="NSytND_fyiM" width="540" height="314" media type="youtube" key="-3xeyZz8xh0" width="420" height="315" <span style="font-family: Verdana,Geneva,sans-serif; font-size: 11.7px;">Video 9: Winner from video 8 defends its shelter effectively with just an attempted chela nip/ charge, ending the interaction quickly. <span style="font-family: Verdana,Geneva,sans-serif; font-size: 90%;">Video 10: Dominant shrimp initiates chase and physical attacks on the subordinate shrimp, resulting in its swimming up (away from the bottom of the tank where the dominant shrimp is) and quick retreats (**Video Credit:** Claudia Tan)

1. Ng P.K.L. (1997) The conservation status of freshwater prawns and crabs in Singapore with emphasis on the nature reserves. //The Gardens' Bulletin Singapore,//**49**(1): 267–272. 2. Cai Y., Naiyanetr P. & Ng P.K.L.(2004) The freshwater prawns of the genus Macrobrachium Bate, 1868, of Thailand (Crustacea: Decapoda: Palaemonidae). //Journal of Natural History//, **38**(5): 581–649. 3. Ng P.K.L. (1992) The freshwater crabs and palaemonid prawns (Crustacea: Decapoda) of Batam Island, Riau Archipelago, Indonesia, including descriptions of two new species. In: //Proceedings of The Biological Society of Washington.// (Ed C.B. Robbins), Allen Press Inc.: Lawrence, Kansas. p. 896. 4. Chong S.S.C. & Khoo H.W. (1987) //Macrobrachium malayanum// (Roux, 1934) stat. nov. (Decapoda, Palaemonidae) as a synonym of //M. geron// Holthuis, 1950, with notes on its distribution. //Journal of Natural History//, **21**(4): 903–913. 5. Wowor D., Cai Y. & Ng P.K.L. (2004) Crustacea: Decapoda, Caridea. In: //Freshwater Invertebrates of the Malaysian Region.// (Eds C.M. Yule & H.S. Yong). Academy of Sciences of Malaysia: Malaysia. pp. 337–356. 6. Ng P.K.L. (1995) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">Freshwater Decapod Crustaceans. In: //Rain forest in the city: Bukit Timah Nature Reserve, Singapore.// (Ed S.C. Chin).Gardens' bulletin, Singapore, Vol. 3. National Parks Board, Singapore. pp. 151 –<span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">157. 7. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">Ho J.K.I., Ramchunder S., Memory A., Meryl T., Li T.J., Yeo D.C.J., Esther C., Cai Y. & Tan H.H. (in press) //A Guide to the Freshwater Fauna in the Nee Soon Swamp Forest//, Singapore. p. 146. 8. Dudgeon D. (1999) The zoobenthos: a systematic review. In: //Tropical Asian streams : zoobenthos, ecology and conservation//, (Ed D. Dudgeon). Hong Kong University Press: Hong Kong. pp. 93–518. 9. Ng P.K.L. (1990) Freshwater Crabs and Prawns of Singapore. In: //Essays in zoology : papers commemorating the 40th anniversary of the Department of Zoology, National University of Singapore// (Ed.s L.M. Chou & P.K.L. Ng). Department of Zoology, National University of Singapore: Singapore. pp. 189–201. 10. <span style="font-family: Arial,Helvetica,sans-serif;">Holthuis L.B. (1950) The Decapoda of the Siboga Expedition. Part X. The Palaemonidae collected by the Siboga Snellius Expeditions with remarks on other species. Subfamily Palaemoninae, Brill, E. J., Leiden, Holland. p. 268. 11.Roux J. (1934) New freshwater decapod crustaceans from the Malay Peninsula. T//he Bulletin of the Raffles Museum//, 1934. **9**:28–33. 12.Bishop J.E. (1973) The Invertebrate Fauna. In: //Limnology of a Small Malayan River Sungai Gombak,// (Ed J.E. Bishop). Springer: Netherlands. pp. 187–342. 13. Ng P.K.L. & Lim K.K.P. (1992) The conservation status of the Nee Soon freshwater swamp forest of Singapore. //Aquatic Conservation: Marine and Freshwater Ecosystems//, **2**(3): 255–266. 14. Tok C.Q.Y. (2013) //Population study on the freshwater shrimps in Nee Soon Swamp Forest, Singapore.// Thesis. School of Biological Sciences, Nanyang Technological University, Singapore. 15. Johnson D. (1963) Distributional and other notes on some freshwater prawns (Atyidae and Palaemonidae) mainly from the Indo-West Pacific region. //Bulletin of the National Museum of Singapore//, **32**:5–30. <span style="font-family: Arial,Helvetica,sans-serif;">16. Johnson D. (1967) Some factors influencing the distribution of freshwater prawns in Malaya. //Proceedings of the Symposium on Crustacea, Marine Biological Association of India//. 1:418–433. 17. Mantel S.K.& Dudgeon D. (2004) Dietary variation in a predatory shrimp //Macrobrachium hainanense// (Palaemonidae) in Hong Kong forest streams. //Archiv für Hydrobiologie//, **160**(3): 305<span style="font-family: Arial,Helvetica,sans-serif;">– 328. 18. Jimoh A.A., Clarke E.O., Whenu O.O. & Adeoye H.B. (2011) //Food and feeding habits of the African river prawn (Macrobrachium vollenhovenii,// Herklots, 1857) in Epe Lagoon, southwest Nigeria. //International Journal of Fisheries and Aquaculture//, **3**(1): 10<span style="font-family: Arial,Helvetica,sans-serif;">– 15. 19. Joseph I., Bassey A., George E. & Ubong G. (2013) Food and Feeding Habits of the Brackish River Prawn //(Macrobrachium macrobrachion,// Herklots, 1857) from Great Kwa River, Obufa Esuk Beach, Calabar, Cross River State, Nigeria. //Journal of Natural Sciences Research,// **3**(9): 82<span style="font-family: Arial,Helvetica,sans-serif;">– 87. 20. Tan, H.H. (2014) Malayan freshwater shrimps attacking forest halfbeak. //Singapore Biodiversity Records//, **145.** 21. <span style="font-family: Arial,Helvetica,sans-serif;">Crowl T.A., Mcdowell W.H., Covich A.P. & Johnson S.L. (2001) Freshwater shrimp effects on detritial processing and nutrients in a topical headwater stream. //Ecology//, **82**(3): 775–783. 22. Moulton T., Magalhães-Fraga S.P., Brito E. & Barbosa F. (2010) Macroconsumers are more important than specialist macroinvertebrate shredders in leaf processing in urban forest streams of Rio de Janeiro, Brazil. //Hydrobiologia//, **638**(1): 55<span style="font-family: Arial,Helvetica,sans-serif;">– 66. 23.March J.G., Pringle C.M., Townsend M.J. & Wilson A.I. (2002) Effects of freshwater shrimp assemblages on benthic communities along an altitudinal gradient of a tropical island stream. //Freshwater Biology//, **47**(3): 377–390. 24.Rosemond A.D., Pringle C.M. & Ramírez A. (1998) Macroconsumer effects on insect detritivores and detritus processing in a tropical stream. //Freshwater Biology//, **39**(3): 515<span style="font-family: Arial,Helvetica,sans-serif;">– 523. 25. Boulton A.J., Boyero L., Covich A.P., Dobson M., Lake S. & Pearson R. (2008) Are Tropical Streams Ecologically Different from Temperate Streams? In: //Tropical Stream Ecology// (Ed D. Dudgeon). Academic Press: London. pp. 257<span style="font-family: Arial,Helvetica,sans-serif;">– 284. 26. Barki A., Karplus I. & Goren M. (1991) The Agonistic Behaviour of the Three Male Morphotypes of the Freshwater Prawn //Macrobrachium Rosenbergii// (Crustacea, Palaemonidae). //Behaviour,// **116**(3): 252–276. 27. Lee C.L. & Fielder D.R. (1983) Agonistic behaviour and the development of dominance hierarchies in the freshwater prawn, //Macrobrachium australiense// Holthuis, 1950 (Crustacea: Palaemonidae). //Behaviour//, **83**(1):1–16. 28. Goessmann C., Hemelrijk C. & Huber R. (2000) The formation and maintenance of crayfish hierarchies: behavioral and self-structuring properties. //Behavioral Ecology and Sociobiology//, **48**(6): 418–428. 29. Vannini M. & Gherardi F. (1981) Dominance and individual recognition in //Potamon fluviatile// (decapoda, brachyura): possible role of visual cues. //Marine Behaviour and Physiology//, **8**(1):13–20. 30.Fero K., Simon J.L., Jourdie V. & Moore P.A. (2007) Consequences of social dominance on crayfish resource use. //Behaviour//, **144**(1):61–82. 31.Hock K. & Huber R. (2007) Effects of fighting decisions on formation and structure of dominance hierarchies. //Marine and Freshwater Behaviour and Physiology//, **40**(1): 45–61. 32. Peebles J.B. (1980) Competition and habitat partitioning by the Giant freshwater prawn //Macrobrachium rosenbergii// (De Man) (Decapoda, Palaemonidae). //Crustaceana//, **38**(1): 49–54. 33. Fero K. & Moore P. (2008) Social spacing of crayfish in natural habitats: what role does dominance play? //Behavioral Ecology and Sociobiology//, **62**(7):1119–1125. 34. Gherardi F. & Cioni A. (2004) Agonism and interference competition in freshwater decapods//.// //Behaviour//, **141**(10): 1297–1324. 35. Karplus I. (2005) Social control of growth in //Macrobrachium rosenbergii// (De Man): a review and prospects for future research. //Aquaculture Research//, **36**(3): 238–254. 36. Kulesh V. (2009) Effect of biotic factors on growth and survival of the Oriental river prawn //Macrobrachium nipponense// (De Haan) in warm-water aquaculture. //Russian journal of ecology//, **40**(6): 405–414. 37. Moraes-Valenti P.M.C. & Valenti W.C. (2007) Effect of Intensification on Grow Out of the Amazon River Prawn, //Macrobrachium amazonicum.// //Journal of the World Aquaculture Society//, **38**(4): 516–526. 38. Lan L.M., Micha J.-C., Long D.N. & Yen P.T. (2006) Effect of densities and culture systems on growth, survival, yield, and economic return of freshwater prawn, //Macrobrachium rosenbergii// farming in the rice field in the Mekong Delta, Vietnam. //Journal of Applied Aquaculture,// **18**(1): 43–62. 39. Karplus I. & Harpaz S. (1990) Preliminary observations on behavioral interactions and distribution patterns of freshwater prawns //Macrobrachium Rosenbergii// under semi-natural conditions (Decapoda, Caridea)//.// //Crustaceana//, **59**(2): 193–203. 40. Lammers J.H., Warburton K. & Cribb B.W. (2009) Diurnal Refuge Competition in the Freshwater Prawn. //Journal of Crustacean Biology//, **29**(4): 476–483. 41. Vogt G. (2013) Abbreviation of larval development and extension of brood care as key features of the evolution of freshwater Decapoda. //Biological Reviews//, **88**(1): 81–116. 42. Wowor D., Muthu V., Meier R., Balke M., Cai Y. & Ng P.K.L. (2009) Evolution of life history traits in Asian freshwater prawns of the genus Macrobrachium (Crustacea: Decapoda: Palaemonidae) based on multilocus molecular phylogenetic analysis. //Molecular Phylogenetics and Evolution//, **52**(2): 340–350. 43. Wheatly M. (1993) Physiological Adaptations in Decapodan Crustaceans for Life in Fresh Water. In: //Advances in Comparative and Environmental Physiology (Volume 15): Advances in Comparative and Environmental Physiology//. Springer: Berlin Heidelberg. pp. 77<span style="font-family: Arial,Helvetica,sans-serif;">– 132. 44. Anger K. (1995) The conquest of freshwater and land by marine crabs: adaptations in life-history patterns and larval bioenergetics. //Journal of Experimental Marine Biology and Ecology//, **193**(1):119<span style="font-family: Arial,Helvetica,sans-serif;">– 145. 45. Vernberg B.W. & Vernberg F.J. (1983) Freshwater Adaptations. In: //The Biology of Crustacea (Volume 8): Environmental Adaptations// (Ed.s F.J. Vernberg & B.W. Vernberg) Academic Press: London. pp. 335–359. 46. Chong S.S. & Khoo H. (1987) The abbreviated larval development of the freshwater prawn, //Macrobrachium malayanum// (Roux, 1934)(Decapoda, Palaemonidae), reared in the laboratory. //Crustaceana//, **53**(1): p. 29<span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">– 42. 47. Atkinson J.M. (1977) Larval development of a freshwater prawn, //Macrobrachium lar// (Decapoda, Palaemonidae), reared in the laboratory. //Crustaceana//, **33**(2): 119–132. <span style="font-family: Arial,sans-serif; font-size: 10pt;">48. Ngoc <span style="font-family: 'Cambria Math',serif; font-size: 10pt;">‐ <span style="font-family: Arial,sans-serif; font-size: 10pt;">Ho N. (1976) The larval development of the prawns //Macrobrachium equidens// and //Macrobrachium// sp.(Decapoda: Palaemonidae), reared in the laboratory. //Journal of Zoology//, **178**(1):15– 55. <span style="font-family: Arial,sans-serif; font-size: 10pt;">49. Kwon C. & Uno Y. (1969) The larval development of //Macrobrachium nipponense// (De Haan) reared in the laboratory. //La mer//, **7**(4): 30– 46. <span style="font-family: Arial,sans-serif; font-size: 10pt;">50. Mashiko K. (1990) Diversified egg and clutch sizes among local populations of the fresh-water prawn //Macrobrachium nipponense// (de Haan). //Journal of Crustacean Biology//, **10**(2): 306– 314. <span style="font-family: Arial,sans-serif; font-size: 10pt;">51. Mashiko K. (1983) Differences in the egg and clutch sizes of the prawn //Macrobrachium nipponense// (de Haan) between brackish and fresh waters of a river//.// // 動物学雑誌 //<span style="font-family: Arial,sans-serif; font-size: 10pt;">, **92**(1): 1– 9. <span style="font-family: Arial,sans-serif; font-size: 10pt;">52. Chong, S.S. & Khoo H. (1988) The identity of //Macrobrachium lanchesteri// (De Man, 1911) (Decapoda, Palaemonidae) from Peninsular Malaysia and Singapore, and a description of its first zoea. //Crustaceana//, **54**(2): 196– 206. <span style="font-family: Arial,sans-serif; font-size: 10pt;">53. Ng P.K.L. & Chong S. (1992) A note on the taxonomy and larvae of the acid water prawn, //Macrobrachium trompii// (De Man, 1898)(Crustacea: Decapoda: Caridea: Palaemonidae). //Malayan Nature Journal//, **46**: 119– 129. <span style="font-family: Arial,sans-serif; font-size: 10pt;">54. Shokita S., Takeda M., Sittilert S. & Polpakdee T. (1991) Abbreviated larval development of a fresh-water prawn, //Macrobrachium niphanae// Shokita and Takeda (Decapoda: Palaemonidae), from Thailand. //Journal of Crustacean Biology//, **11**(1): 90– 102. <span style="font-family: Arial,sans-serif; font-size: 10pt;">55. Jalihal D.R., Sankolli K.N. &. Shenoy S. (1993) Evolution of Larval Developmental Patterns and the Process of Freshwaterization in the Prawn Genus Macrobrachium Bate, 1868 (Decapoda, Palaemonidae). //Crustaceana//, **65**(3): 365– 376. <span style="font-family: Arial,sans-serif; font-size: 10pt;">56. Mashiko K. (1985) Comparison of Survival and Development between Large and Small Neonates of a Freshwater Prawn under Starvation Conditions (Behavior Biology and Ecology). //Zoological Science//, **2**(3): 397– 403. <span style="font-family: Arial,sans-serif; font-size: 10pt;">57. Karge, A & Klotz W. (2008) Süßwassergarnelen aus aller Welt [Fresh water shrimps of the world], Vol. 2. Ettlingen: Auflage. 216 p. <span style="font-family: Arial,sans-serif; font-size: 10pt;">58. Liu M.Y., Cai Y.X. & Tzeng C.S. (2007) Molecular systematics of the freshwater prawn genus //Macrobrachium// Bate, 1868 (Crustacea: Decapoda: Palaemonidae) inferred from mtDNA sequences, with emphasis on East Asian species. Zoological Studies, **46**(3): 272– 289. <span style="font-family: Arial,sans-serif; font-size: 10pt;">59. Rabalais, N.H. & Gore R.H. (1985) Abbreviated development in decapods. In: //Crustacean Issues (Volume 2): Larval Growth// (Ed. A.M. Wenner). A. A. Balkema: Rotterdam. pp. 67– 126. <span style="font-family: Arial,sans-serif; font-size: 10pt;">60. Murphy N.P. & Austin C.M. (2005) Phylogenetic relationships of the globally distributed freshwater prawn genus //Macrobrachium// (Crustacea: Decapoda: Palaemonidae): biogeography, taxonomy and the convergent evolution of abbreviated larval development. //Zoologica Scripta//, **34**(2):187– 197. 61. Page T.J., Short J.W., Humphrey C.L., Hillyer M.J. & Hughes J.M. (2008) Molecular systematics of the Kakaducarididae (Crustacea: Decapoda: Caridea). //Molecular Phylogenetics and Evolution//, **46**(3):1003–1014. 62. Short J.W., Humphrey C.L. & Page T.J. (2013) Systematic revision and reappraisal of the Kakaducarididae Bruce (Crustacea : Decapoda : Caridea) with the description of three new species of Leptopalaemon Bruce & Short. //Invertebrate Systematics,// **27**(1):87–117. 63. Kou Q., Li X., Chan T.-Y., Chu K.H. & Gan Z. (2013) Molecular phylogeny of the superfamily Palaemonoidea (Crustacea : Decapoda : Caridea) based on mitochondrial and nuclear DNA reveals discrepancies with the current classification. //Invertebrate Systematics,// **27**(5):502–514 64. De Grave S., Fransen C.H. & Page T.J. (2015) Let’s be pals again: major systematic changes in Palaemonidae (Crustacea: Decapoda). //PeerJ,// **3,** e1167. 65. Pileggi L.G. & Mantelatto F.L. (2010) Molecular phylogeny of the freshwater prawn genus //Macrobrachium// (Decapoda, Palaemonidae), with emphasis on the relationships among selected American species. //Invertebrate Systematics,// **24**(2):194–208. 66. De Grave S., Cai Y. & Anker A. (2008) Global diversity of shrimps (Crustacea: Decapoda: Caridea) in freshwater. In: //Freshwater Animal Diversity Assessment// (Ed.s E.V. Balian, C. Lévêque, H. Segers & K. Martens) Springer: The Netherlands. pp. 287–293. 67. Jalihal D.R., Sankolli K.N. & Shenoy S. (1993) Evolution of Larval Developmental Patterns and the Process of Freshwaterization in the Prawn Genus Macrobrachium Bate, 1868 (Decapoda, Palaemonidae). //Crustaceana,// **65**(3):365–376. 68.Murphy N.P. & Austin C.M. (2004) Multiple origins of the endemic Australian //Macrobrachium// (Decapoda : Palaemonidae) based on 16S rRNA mitochondrial sequences. //Australian Journal of Zoology,// **52**(5): 549–559. 69. Santini F. & Winterbottom R. (2002) Historical biogeography of Indo‐western Pacific coral reef biota: is the Indonesian region a centre of origin? //Journal of Biogeography,// **29**(2):189–205. 70. De Bruyn M., Wilson J.A. & Mather P.B. (2004) Huxley’s line demarcates extensive genetic divergence between eastern and western forms of the giant freshwater prawn, Macrobrachium rosenbergii. //Molecular Phylogenetics and Evolution,// **30**(1): 251–257.
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