Introduction


Food, Friend or Foe?

When you think of stingrays, what is the first thing that comes to mind?

Opening picture TL.png
Fig. 1. Friend, food or foe? Top left image by Two Travelling Moms (Edited). Pending permission. Top right image by Melba Sta Ana. Used with permission. Bottom left by Rob Atherton (Edited). Used with permission.


Whether food, friend or foe, stingrays are essentially fish. Yes, you read that right. Stingrays are fish. But delicious as they may be as a food source in Southeast Asia, Australia and East Africa[1] , it is unfortunate that stingrays have earned a reputation of being dangerous and venomous creatures even when they are, in fact, considered timid and docile creatures by most experts. No doubt they are venomous with their tail spines but they are usually only used in self-defence (such as being accidentally stepped on) or when they feel threatened. With exceptions such as Steve Irwin’s death on 4th September 2006 and 81-year-old James Bertakis’ incident, both of whom were stabbed in the chest by a stingray[2], stingray-related injuries to humans typically occur in the lower parts of the body (due again to accidentally stepping on them) and are rarely fatal. The venom causes an excruciating pain but it is rarely deadly to humans (maybe except when delivered to critical areas) and the wound can even be treated if it is not too serious (read more about Defence Mechanisms)[2] .

Now, even if we consider them as friendly, not-so-dangerous creatures, the way that we treat them still leaves much to be desired (read more about Conservation Status and Threats). We will see that this is especially problematic as we now turn our attention to one of the most abundant, beautiful and iconic stingrays to inhabit the nearshore, coral reef-associated habitats of the Indo-West Pacific region[1]. This is none other than the...

BLUE-SPOTTED FANTAIL RAY (Taeniura lymma)


Belonging to the stingray family Dasyatidae (whiptail stingrays), T. lymma is a cartilaginous fish (their skeletal system is made of cartilage rather than bone like humans and other vertebrates) that is common throughout the tropical Indian and western Pacific Oceans, with a range that begins from the intertidal zone and extends up to a depth of 30 metres (100 feet). It can grow up to 35cm across and 80cm long, with a weight of up to 5kg[1].

Conservation Status and Threats

Given the charismatic looks of T. lymma (read more about Physical Description), it is not surprising that it is perceived more as a friend rather than food or foe. But are we really treating it as such? Our actions actually say otherwise.

Done_Status 2.png
Fig. 2. IUCN status. Image retrieved from International Union for Conservation of Nature.

There is currently no data on the local status of T. lymma in Singapore but ever since 2005, T. lymma has been listed as "Near Threatened" (global status) under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species[3] . This is due to the following human activities and practices that continue to threaten its survival.

1. Habitat Destruction
2. Over-fishing
3. Aquarium Trade
With the rise in global population and the demand for space and resources, coastal development has been rapidly increasing over the years, as evident from land reclamation works. This has contributed to the degradation of coral reefs, which essentially translates to fewer and less viable habitats for T. lymma throughout its range [1].[4] [5] Degradation of coral reef habitats for T. lymma can also be attributed to climate change as well as destructive fishing practices that use cyanide or dynamite [1].
Taeniura lymma faces intensive fishing pressure throughout its range, be it being caught intentionally as food or gamefish, or unintentionally as bycatch. With fishing practices that utilize gillnets, longlines, spears and fence traps, all of which extend to the bottom of the sea floor and catch fish indiscriminately, it is no wonder T. lymma can get caught or trapped in them[1][4].
As an attractive creature, T. lymma is popular with home aquarists as an aquarium pet[1][4][5] and is in fact, the most common stingray found in private home aquariums[1]. This is despite the fact that it does not fare well in captivity[1][4][5], with individuals outgrowing the aquariums[5], and even those seemingly healthy ones suddenly dying or refusing to feed[1].

Having a positive image as a "friend" is generally perceived as a good thing. Especially in the field of conservation, it is likely the case that there will be less human-wildlife conflict and more reasons for protecting the organisms of interest and/or its habitat than removing or exterminating them, if it is seen positively. But having this positive image is only good until it starts to backfire and ironically cause more harm upon the organism, as evident from the involvement of T. lymma in the aquarium trade. The important conservation message here then is that charismatic creatures such as T. lymma are most beautiful when free to roam about in their natural habitats, not when they are kept in captivity whiile their natural habitats get destroyed by human activities.

A Common Mix-up

Notice how so far, we have been using the scientific name (T. lymma) rather than the common name (blue-spotted stingray) when referring to this species of interest? Well, that is because this species goes by several common names, both English and non-English[1][3][6] (Fig. 3) and the scientific name is the most straightforward and unambiguous way of referring to this species. The following figure presents some of the common names of T. lymma in selected languages used within the region it can be found in (read more about Geographical Range and Distribution).

TL_Common names2.png
Fig. 3. Common names in selected languages

From one glance, it is easy to see how the common name of this species came about. 1) It is a stingray. 2) It has blue spots (read more about Distinctive Features). It makes sense for easier general communication if it was the only stingray with blue spots but guess what? There is another stingray species called Neotrygon kuhlii which also has blue spots and is, coincidentally, also known commonly as the blue-spotted (sting)ray (see the names in red) or Kuhl’s stingray[7] . Not to mention that this second species also tends to occupy the same kind of habitat - inshore over coral reefs[4] (read more about Habitat) - which further complicates things. Hence, scientists have devised a standardized naming system with vigorous rules to avoid such confusion. For more information on how scientific names work, check out this page. Having said all that, for the rest of this page, we will continue to use the scientific names of species.

DID YOU KNOW?
All of this mix-up seems to originate from two main things. On one hand, we have N. kuhlii, which is found almost everywhere in the world except the Red Sea and is commonly called the “blue-spotted (sting)ray”. On the other hand, T. lymma, which is actually found in the Red Sea and referred to as the “blue-spotted fantail/ribbiontail ray” everywhere else, is known by locals near the Red Sea as *the* “blue-spotted (sting)ray” since it is the only stingray that locals have seen in the region[8] .

A New Discovery!!!

Considering how recognizable and popular T. lymma is, it is reasonable to think that there would not be an surprises left in store for us but... we were wrong. In fact, just earlier this year in 2016, researchers have split the existing T. lymma species into two separate species, with the newly described one called Taeniura lessoni[9] . In light of this, besides providing some general information on stingrays, with a focus on the species T. lymma, this page also aims to resolve part of the prevailing confusion by providing some diagnostic features that can allow one to tell T. lymma apart from species it is can be confused with such as N. kuhlii and T. lessoni (read more about Species Diagnosis and Identification). Fret not if some of the terms used get a little technical at times for explanations to these terms are provided where possible and links to the definitions of these terms are also given in cases where a short explanation is insufficient. You will also find many videos and pictures that accompany the information. The section on Taxonomy and Systematics will be the most technical section but do challenge yourself to read it to gain a better understanding of how T. lymma got its current name and more

Physical Description


Distinctive Features

Taeniura lymma is a fairly small ray with a rounded snout[10] and numerous striking iridescent blue spots adorning its olive-green, dorsoventrally compressed, oval body[1][5][10]. The spots vary in size and generally become smaller and increase in density towards the edge of the body disc[1]. A pair of distinctive blue stripes also runs along each side of its tail[1][5] which is equipped with one or two (usually two) venomous tail spines near the end of the tail (Fig. 6)[4][10].This is contrary to the popular belief that tail spines are located at the end of the tail. Overall, its brightly-coloured skin serves as a warning to other animals that it Is venomous[5]. While some individuals off Southern Africa have been found to lack the blue stripes on the tail[1], it has been recently proposed that they are a new species distinct from T. lymma (read more about T. lessoni at Species Diagnosis and Identification).

Main Body

Taeniura lymma has generally smooth skin, with the exception of some small thorns scattered down the middle of its back in adults. On the dorsal side (upper side of the body), T. lymma also has large, broad spiracles which are located right behind large, bulbous eyes that are bright yellow in colour[1][4] [11] (Fig. 9). Its pectoral fins are estimated to be approximately four-fifths as wide as it is long and its pelvic fins are narrow and angular[1].

dorsal.jpg
Fig. 4. Dorsal view. Image by Rokus Groeneveld (Edited). Used with permission.

Its mouth, gills, nares (naris if singular) and cloaca (Fig. 8) are found on its ventral side (underside of the body), which is uniformly white in colour[1][4][5].The location of the mouth makes T. lymma adapted to efficiently scoop up animals hiding in the seafloor bed while its white underside provides some camouflage against the sunny waters above when it is viewed from below (countershading)[5]. Between the nares, reaching past the mouth, there is also a narrow flap of skin with a fringed posterior (nearer the rear end of the stingray) margin. Meanwhile, the lower jaw dips at the middle with deep furrows at the corners of the mouth[1]. Within the mouth, numerous small teeth are arranged in two plates that are adapted for crushing the shells of their prey[4][5] (read more about Feeding). This crushing power is aided by their strong yet lightweight jaws which have been strengthened due to several layers of calcified cartilage supported by hollow, mineralized struts[12] .

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Fig. 5. Ventral View. Left image retrieved from the © Australian Museum (Edited). Right image by Ron DeCloux (Edited). Used with permission.

Tail and Tail Spines

Taeniura lymma has a thick, depressed tail that tapers at the end[4]. Measuring about 1.5 times the length of the body disc so as to allow it to strike enemies directly in front[8], the tail has a low midline ridge on the dorsal surface and a broad skinfold (or fin fold) on the ventral surface that reaches the tip of the tail[1][4]. This ventral skinfold is the very structure that contributes the “ribbontail” part to one of the common names of T. lymma[10].

As mentioned above, the tail of T. lymma usually has one or two venomous tail spines that are located near the base of the tail. These tail spines are serrated[1] with sharp barbs that face the body of the stingray[2] and narrow grooves that run lengthwise along the undersides. This entire tail spine structure is then covered by a thin layer of skin that acts like a sheath[4] (read more about how the tail is used for defence at Defence Mechanisms).


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Fig. 6. Close-up view of tail. Image by Rob Atherton (Edited). Used with permission.

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Fig. 7. Close-up view of tail spine. Pending permission.

DID YOU KNOW?
The tail spines of stingrays have been used to make weapons such as daggers[8].


Males versus Females

The males and females of Taeniura lymma, similar to most other stingrays and cartilaginous fish, look physically different. We describe these creatures as "sexually dimorphic". "Dimorphic" comes from the Greek words 'di-' and 'morphe' which translates to 'having two forms'[13] and the term that describes this phenomenon in T. lymma is "sexual dimorphism". Sexual dimorphism in stingrays manifests in many ways, one of which is evident from size and the presence of a pair of claspers near the pelvic fin. Claspers are male anatomical structures that are used to channel semen into females via their cloaca during mating. Females are typically larger than males and as shown in the figure below, male stingrays possess claspers whereas female stingrays do not[14] .

Claspers.jpg
Fig. 8. Comparing anatomy of males and females. Image by King Bee Chen (Edited). Used with permission.

Taeniura lymma also exhibits sexual dimorphism in the electrosensory system (read more about Sensory Mechanisms) with the males possessing a significantly lower total abundance of electrosensory nerve axons compared to the females. From this, it has been suggested that the greater number of electrosensory nerve axons in females may help in improving their sensitivity, thus allowing them to differentiate between approaching their own kind and potential predators, as well as to better identify suitable males for mating (read more about Reproduction and Breeding)[15] .

Species Diagnosis and Identification


As previously mentioned, T. lymma is often confused with N. kuhlii, both of which share the common name “blue-spotted (sting)ray” and are found in similar habitats. To avoid making such a mistake, simply look out for some of the diagnostic features of each species in the figures below[16] .
Face comparison.jpg
Fig. 9. Close-up comparison. Left image by Rob Atherton (Edited). Right image by Shawn M. Miller (Edited). Used with permission.

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Fig. 10. Full body comparison. Left and right images by Marc Baldwin (Edited). Used with permission.

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Fig. 11. Distinguishing feature of the new species. Image by Arthur Chapman (Edited). Used with permission.

Geographical Range and Distribution


Worldwide

Said to be widespread in the Indo-West Pacific region[1][4][6][5], T. lymma has a range that extends around the periphery of the Indian Ocean all the way from East Africa to the Arabian Peninsula to Southeast Asia[1], including the Red Sea[4][6][5], Madagascar, Zanzibar, the Seychelles, Sri Lanka, and the Maldives[1]. While also found in the Persian Gulf and the Gulf of Oman[1][6], it is rare in those areas. In the Pacific Ocean, T. lymma has been recorded from the Philippines and Southern Japan to Northern Australia[1][4][6][5] as well as around many Melanesian and Polynesian islands[1] as far east as the Solomon Islands[1][4][5]. However, given the recent discovery of T. lessoni, it is possible that there may be overlaps in their geographical distribution or they may actually be found separately in various areas. More research will need to be conducted to gain a more accurate distribution of the species.

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Fig. 12. Global distribution. Image retrieved from Florida Museum of Natural History. Used with permission.

Singapore

Taeniura lymma is often encountered by divers and can be spotted (no pun intended) on sandy areas or near coral reefs on some of our shores. They have been encountered at the Southern Islands of Singapore such as Saint John’s Island and Sisters’ Island and even at Tanah Merah and Pulau Semakau[10]. The embedded map below shows sightings of T. lymma in Singapore. It was reconstructed from a Flickr Map and last updated on 23rd November 2016.



For more pictures of T. lymma found in Singapore, check out WildSingapore’s webpage here.

Habitat


Taeniura lymma is a bottom-dwelling species[1] that is commonly encountered in shallow temperate and tropical waters over continental shelves[4][5]. Rarely found deeper than 30 metres (100 feet)[1], the blue-spotted fantail ray can be seen on the sandy or rocky bottoms of coral reefs[5], adjacent sandy flats, tidal pools and even near seagrass beds[1].


Adults and juvenile rays are found to occupy dissimilar habitats, with the adults in cool deeper reef environments, and the juveniles in warm, shallow intertidal seagrass, mangal or rocky shoreline habitats[17] .

Biology and Ecology


General Behaviour

A shy creature that swims away when approached by divers[4], T. lymma lives either alone or in small groups[5]. It generally spends the day seeking shelter in reef caves and crevasses, under coral ledges and overhangs[1][4][5], or even in debris such as shipwrecks[1]. Unlike most other stingrays, T. lymma is rarely seen burying itself in the sand[1][4][5] and it often leaves only its tail visible when it goes into hiding[1]. During the high tide, T. lymma migrates in assembled groups from the deeper areas of the reef to the shallower sandy flats to feed (read more about Feeding). They later disperse and take up shelter once again in the deeper areas when the tide starts to recede[1][4][5]. When faced with danger, T. lymma will, in an attempt to shake off predators, flee at high speed in a zigzag pattern[1]. If all else fails, it will then use its venomous tail spines to injure. However, given its shy nature, its tail spines are only used as a last resort[4].The video below showcases the typical shy/defensive behaviour that is exhibited by stingrays, including T. lymma.


Just a word of caution… despite the fact that the stingrays in the video typically flee before having their tails grabbed (from behind and not from the front), do not, under any circumstances, attempt what was done in the video. It goes without saying that if a stingray happens to be startled by a human stepping on them, it will not hesitate to use its tail spines so be careful of where you step (read more about how a stingray actually utilizes its tail spines at Defence Mechanisms).

DID YOU KNOW?
Interestingly, T. lymma has been observed soliciting cleanings from shrimp and tiny fish such as the bluestreak cleaner wrasse (Labroides dimidiatus). How do they do it? They simply head to ‘cleaning stations’ and raise the margins of their disc and pelvic fins [1][5]. Every summer, large numbers of blue-spotted fantail rays also arrive off South Africa[1].


Feeding

Taeniura lymma are predators in benthic habitats within their range, feeding on molluscs, polychaete worms, shrimps, crabs and small fishes[1][4][5][17].They detect their prey via electroreception (read more about Sensory Mechanisms) in which the ray senses electrical fields produced by the prey[5]. However, its potential prey does not include all small fish and invertebrates. This is evident from how some tiny fish and shrimp ‘clean’ T. lymma by picking dead skin and parasites off its body (read more about Predators and Parasites)[5]. Feeding occurs mostly during high tides[4][5] and upon locating the prey, T. lymma excavates sand pits and traps the prey with its body. Using its disc, the ray then carefully manoeuvres the prey into its mouth[1].





DID YOU KNOW? Foraging T. lymma are often followed by other fish, such as the goatfish, that are ready to capture any prey missed by the ray[1].

Predators and Parasites

Hammerhead sharks and bottlenose dolphins are known predators of T. lymma, with other large fish, such as sharks, and marine mammals as potential predators[1][4]



Taeniura lymma is also host to various parasites which include tapeworms, flatworms, nematodes, copepods and protozoans[1].

DID YOU KNOW?
The hammerhead shark avoids injury from the venomous tail spines of Taeniura lymma by using its head to pin the ray to the sea floor while it removes flesh from the dorsal surface of the ray[4].


Reproduction and Breeding

Taeniura lymma, similar to other stingrays, have an (aplacental) ovoviviparous mode of reproduction. This means that female rays give birth to live offspring that have hatched from egg cases within the body[4][5].



During development, the embryos are initially sustained by yolk after which, as they continue to develop and deplete the yolk sac, they receive additional nourishment in the form of histotroph or “uterine milk” (enriched with mucus, fat and proteins) produced by the mother[1][4]. The gestation period is uncertain but has been estimated to last anything from four months up to a year and each time, up to seven offspring can be born[1][4][5]. The young of T. lymma is essentially a miniature version of the adult, measuring 13-14cm across[1][5] and bearing similar markings and the same characteristic blue spots[4][5]. While males reach sexual maturity at a disc width of 20-21cm, not much is known about the maturation size of females[1].

DID YOU KNOW?
The young of stingrays is referred to as a “pup” and a group of them is referred to as a “litter”[1].. To add on to that, a group of stingrays is referred to as a “school” [8].

Breeding usually occurs from late spring and lasts through summer[1][5], with the female T. lymma emitting a chemical signal to indicate to the males that they are receptive. The males, upon detecting the signal with their acutely sensitive ‘nose’[5], start to follow the females and nip at their discs. Eventually, the male will bite and hold onto the female for copulation through internal fertilization[1]. If you like, you can watch the video below from 3:20 onwards.



Defence Mechanisms

It is common knowledge that T. lymma, as a stingray, defends itself using its tail spines and that the two main things that cause the resulting pain are the barbs on the tail spines and the venom that the stingray injects into its victim. But how does a stingray attack? The process is actually pretty simple. The stingray has to first face the victim then all it has to do is to flip its long tail upward and over its body to strike the victim in front[2]. When the tail pierces the skin of the victim, in most cases, the pressure causes the sheath covering the tail spines to tear, thus exposing the sharp barbs of the tail spine and allowing venom to be delivered into the wound through the narrow grooves running lengthwise along the underside of the tail spine (Fig. 7)[2][18] . If you like, you can watch the video below from 1:23 to 2:26.



The venom may not be fatal but it causes excruciating pain for the victim. It consists of the enzymes 5-nucleotidase and phosphodiesterase which essentially cause tissue and cell death, as well as the neurotransmitter serotonin, which causes the severe contraction of smooth muscle. It is the latter that makes the venom especially painful. Fortunately, if the venom is released into an area like the ankle, the wound can usually be treated with the help of heat. Applying heat breaks down the venom and limits the amount of damage it can render. However, in the worst-case scenario, if the wound is not treated in time, amputation might still be necessary[2]. Not to mention that being attacked by a stingray can result in death when the tail spines and/or venom enter critical areas where the major organs are located at.

DID YOU KNOW?
Stingray venom is generally cardiotoxic and even after extracting it from the stingray, the venom remains potent. Yet, despite that, it is said that Ancient Greek dentists once used the venom of stingrays as anaesthetic[8].

As for the barbs on the tail spine, even without the injection of venom, they can do serious damage. While the sharp tip of the tail spine allows it to easily pierce through the skin, having barbs that face the body of the stingray means that any attempts to remove the tail spine will result in the massive tearing of tissue[2].

DID YOU KNOW?
The stingray is able to regenerate its tail spines if it is broken off [18].


Locomotion

In order to generate thrust while keeping their dorsoventrally compressed body mostly rigid[19] , T. lymma exhibits undulatory (wave-like) locomotion in which undulatory waves are propagated down their pectoral fins from the anterior end (nearer the head end of the stingray) to the posterior end (nearer the rear end of the stingray) [20] . To move backwards, all it has to do is to simply reverse the direction of the wave propagation [19].




Taeniura lymma also possess fin muscles that are found throughout the entire length of the pectoral fin and all of them are typically active, except at lower speeds when there is no need for propulsion through the water[18]. [2]Dissection of the pectoral fin muscle has shown that generally, the dorsal (abductor) muscle is used to elevate the fin while the ventral (abductor) muscle is used to depress the fin. To produce the undulatory waves down the pectoral fins, T. lymma alternately lengthens and shortens the dorsal and ventral muscles. The superficial layer was also revealed to mainly consists of red muscle while the deep layer mainly consists of white muscle. The former contributes to the periodic motion of the pectoral fins while the latter is often used for transient motion [19].

Sensory Mechanisms

Ever wondered how stingrays like T. lymma are able to sense their surroundings or even know where to find their prey if their eyes are on the dorsal side while their mouths are on the ventral side? Well, they rely on electroreception to detect prey, navigate and communicate. This is achieved with the help of their peripheral electrosensory system which comprises hundreds to thousands of separate electrosensitive units called the ampullae of Lorenzini, which are tightly grouped into distinct subepidermal clusters. Each of these clusters is linked to an individual pore on the skin via a long canal that is filled with an electrically conductive gel (Fig. 14)[15].

ES pore.jpg
Fig. 14. Image retrieved from Kempster, et al., 2013 [13] (Edited).

Within each individual ampulla, sensory receptor cells line the epithelial wall and these cells have the ability to detect electrical potential differences between the apical side of the gel-filled canal and the basal side of the sensory receptor cell outside the ampulla. These cells allow each ampulla to detect and transduce weak electric fields into electrical impulses which can then be recognized by the nerves of the central nervous system[15]. If that got too technical, then watch this video instead!



For T. lymma, very few electrosensory pores are located on the dorsal side. The majority of them are found on the ventral side of the body instead, concentrated particularly around the mouth. In terms of adaption, this arrangement makes sense since it would facilitate and enhance detection of prey[15].

Taxonomy and Systematics


Taxonomic Hierarchy

Kingdom
Animalia

Phylum
Chordata

Class
Chondrichthyes
(cartilaginous fish)
Subclass
Elasmobranchii
(shark-like fish)
Superorder
Batoidea
(batoids)
Order
Myliobatiformes
(stingrays)
Family
Dasyatidae
(whiptail stingrays)
Genus
TaeniuraMüller and Henle, 1837
(ribbontail rays)
Species
Taeniura lymma(Forsskål, 1775)


Information retrieved from: Integrated Taxonomic Information System (ITIS) and Skates and Rays of Atlantic Canada.
The WoRMS (World Register of Marine Species) taxon tree for the blue-spotted fantail ray can be found here.


Historical Background

The blue-spotted fantail ray, while now known as Taeniura lymma, was not always named as such. The earliest record shows that it was originally described as Raja lymma by Swedish naturalist Peter Simon Forsskål in 1775[1][4] in the book Descriptiones animalium, avium, amphibiorum, piscium, insectorum, vermium / quae in itinere orientali observavit Petrus Forskål. Post mortem auctoris edidit Carsten Niebuhr. Adjuncta est materia medica kahirina atque tabula maris Rubri geographica[21] .

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Fig. 14. Original description. Image retrieved from the Biodiversity Heritage Library (Edited). Click on image to view the full record at Biodiversity Heritage Library.

DID YOU KNOW?
Interestingly, while T. lymma today fall under the class Chondrichthyes for cartilaginous fish, they were actually originally placed under the class Amphibia[21].

It is important to note, however, that sources have inaccurately cited the original description to be in the book Descriptiones animalium quae in itinere ad maris australis terras per annos 1772, 1773, et 1774 suscepto collegit, observavit, et delineavit Joannes Reinlioldus Forster, etc., curante Henrico Lichtenstein. An example is shown in the figure below.
Inaccurate.jpg
Fig. 15. Inaccurate information. Image retrieved from World Heritage Encyclopedia™ [1] (Edited).

In past scientific literature, the blue-spotted fantail ray also went by the name Trygon ornatus after being documented by British zoologist John Edward Gray in 1830[1][4]. In a publication by Gray, titled Illustrations of Indian zoology; chiefly selected from the collection of Major-General Hardwicke[22] , an illustration of T. lymma was included.

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Fig. 16. Illustration by John Edward Gray. Image retrieved from the Biodiversity Heritage Library (Edited). Click on image to view the full record at Biodiversity Heritage Library.

However, as the naming of species works on the Principle of Priority, what Gray had done was to erroneously re-describe a species that already had an assigned species name. Hence, since Trygon ornatus (1830) came after Raja lymma (1775), the former name is now known as a junior synonym. But that is not the end of the story... In 1837, German biologists Johannes Peter Müller and Friedrich Gustav Jakob Henle created the genus Taeniura[1] and grouped the blue-spotted fantail ray within that genus, thus essentially renaming it from Raja lymma to Taeniura lymma

This change in the genus name from 'Raja’ to ‘Taeniura’ was made to better reflect the description of the blue-spotted fantail ray, with particular reference to its tail. ‘Taeniura’ is derived from the Latin word ‘taenia’ meaning ‘stripe’ (or ‘ribbon’ when entered into Google Translate) and the Greek word ‘ουρά’ meaning ‘tail'[4]. Meanwhile, the specific epithet ‘lymma’ is an Arabic word[23] that is said to mean ‘dirt’. No type specimen was designated by Forsskål[1] and no records of the designated type specimen could be found, possibly because it was Johann Christian Fabricius who compiled and edited the manuscript descriptions and names of various fish taxa left behind by Forsskål and Carsten Niebuhr who posthumously published Forsskål's work in 1775[22].

TL name.png

Higher Level Classification

The family Dasyatidae (Order Myliobatiformes) is one of the biggest families of batoid fishes, and the members within this family have a body that is “characterized by a large, oval, circular or rhomboidal disc usually covered with denticles, thorns and tubercles on the dorsal surface and sometimes on the tail”. However, given the large number of species described in the family Dasyatidae as well as taxonomic uncertainties, the classification and status of some species are still subject to change, especially at the family level (read more about Taxonomic Hierarchy)[24] .

Phylogeny and Morphology

There are many taxonomic issues within rays, including the family Dasyatidae. Recently, these issues have become even more contentious based on studies that were conducted just two to three years ago. In fact, the discovery of the new species T. lessoni this year is just the tip of the iceberg. Within the genus Taeniura itself, there are issues of species placement. While some taxonomic sources recognize three species in the genus Taeniura (note that back then, T. lessoni was not discovered yet), others have removed the species T. grabata and T. meyeni and placed them in the genus Taeniurops instead[25] . Of course, this means that T. lymma was the sole member of the genus for a while until T. lessoni came along (read more about T. lessoni at Species Diagnosis and Identification).

A study that proposed such a change in species placement was one that was conducted by Lim et al. (2015) with the following aims[24]:

  1. Elucidate the phylogenetic relationships of stingrays in the family Dasyatidae using COI, ND2 and RAG1 genes
  2. Re-examine the morphological characters used by Last et al. (2010) for species differentiation in the book “Sharks and Rays of Borneo” (Collingwood: CSIRO Marine and Atmospheric Research)

This was the first time these genes (or even any other genes for that matter) were successfully studied at the family level for rays and based on the results, it was suggested that the current family Dasyatidae is non-monophyletic and should be split, instead, into four different families – Neotrygonidae, Himanturidae, Pastinachidae and Dasyatidae – including itself. The results that they obtained are summarized in the respective trees below. Note that for the RAG1 gene, a cladogram was generated instead as the short distances among the taxa resulted in a crowded phylogenetic tree[24].

Done_Combined.jpg
Fig. 17. Trees for the COI, ND2 and RAG1 genes respectively. Image retrieved from Lim,et al., 2015 [22] (Edited). Click on image to view the enlarged trees.

It would be most ideal if a summarized tree using all three of the genes was generated. However, this was not done so in the study proposed by Lim et. al (2015). Nevertheless, all of the trees show that the Dasyatidae family (boxed up in green) is not monophyletic, forming four clades for the COI and RAG1 genes and two main clades (each with two subclades) for the ND2 gene. Hence, in order to maintain monophyly, the researchers proposed the following changes in classification in their discussion[24]:
  • Elevation of the three clusters to family level (three new families)
  • Retain original Dasyatidae family (Dasyatis and Taeniurops spp.)
  • 1st new family: Neotrygonidae (Neotrygon spp. and Taeniura lymma)
  • 2nd new family: Himanturidae (Himantura spp.)
  • 3rd new family: Pastinachidae (Pastinachus spp.)

It is interesting to note that after resolving the problem of non-monophyly, members of the order Myliobatiformes could be accurately and correctly classified into their respective families based on morphology, using nine character measurements that have been identified as useful morphological information and removing previously used characters that caused incertae sedis (uncertain placements) and/or past misclassifications[24].

These characters are relative total length (TL), disc length (DL), tail width (TW), tail height (TH), eye diameter (ED), spiracle length (SPL), interspiracular length (ISL), distance between fifth gill slits (I5) and ventral tail fold length (VFL). These were the findings observed[24]:

  • Neotrygonidae are separated from the other families by their relatively large ED
  • Himanturidae have no fin fold and the longest DL
  • Pastinachidae are separated from the rest by their relatively longer VFL

Genetic Sequences

In early 2015, the complete mitogenome of T. lymma was also sequenced and it was found to be 17,652 basepairs long (GenBank accession number: KM881715), containing 37 mitochondrial genes and a non-coding AT-rich region of 1906 basepairs in length. The base composition of the T. lymma mitogenome is A: 32.09%, T: 27.04%, G: 13.00% and C: 27.87%. Mitogenome comparisons indicate has a closer relationship between T. lymma and N. kuhlii (88%) than between T. lymma and T. meyeni (85%). This is consistent with previous analyses done based on the mitochondrial COI and 16S genes and the nuclear RAG1 markers, as well as the aforementioned phylogenetic study by Lim et al. (2015). Given the many unresolved questions with regards to the taxonomic boundaries in rays, the mitogenomic information for Taeniura will be a useful molecular resource for future studies[25].

A representative barcode sequence (the centroid of all available sequences) for T. lymma is shown below.

Barcode.png
Fig. 18. DNA Barcode. Image retrieved from Encyclopedia of Life.

Beyond This Page


External Links


Animal Diversity Web
ARKive
The Elasmodiver Shark and Ray Field Guide
Encyclopedia of Life
Florida Museum of Natural History
A Guide to Common Marine Fishes of Singapore
IUCN Red List
MarineBio
Wild Fact Sheets (Wild Singapore)


References


  1. ^ “Bluespotted Ribbontail Ray,” by Word Heritage Encyclopedia. Project Gutenberg Self-Publishing Press, n.d. URL: http://www.gutenberg.us/article/whebn0007236481/bluespotted%20ribbontail%20ray (accessed on 8 Oct 2016).
  2. ^ “How Do Stingrays Kill?” by Julia Layton. How Stuff Works, 21 May 2008. URL http://animals.howstuffworks.com/fish/stingray.htm (accessed on 2 Nov 2016).
  3. ^Taeniura lymma,” by Compagno, L. J. V. The IUCN Red List of Threatened Species, 2005. URL: http://dx.doi.org/10.2305/IUCN.UK.2005.RLTS.T39412A10229354.en. (accessed on 2 Nov 2016).
  4. ^Taeniura lymma,” by Cathleen Bester. Florida Museum of Natural History, n.d. URL: http://www.flmnh.ufl.edu/index.php?cID=1861 (accessed on 8 Oct 2016).
  5. ^ “Ribbontailed Stingray (Taeniura lymma),” by Wildscreen ARKive. ARKive, n.d. URL: http://www.arkive.org/ribbontailed-stingray/taeniura-lymma/ (accessed on 8 Oct 2016).
  6. ^ “Species Details: Taeniura lymma (Forsskål, 1775),” by R. Froese & D. Pauly. Species 2000 & ITIS Catalogue of Life, Aug 2016. URL: http://www.catalogueoflife.org/col/details/species/id/d9d9d9cb5f1f291499fe981486841924 (accessed on 8 Oct 2016).
  7. ^Neotrygon kuhlii,” by Fahmi, W. T. White & I. P. Jacobsen. The IUCN Red List of Threatened Species 2015, n.d. URL: http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T161590A68636167.en (accessed on 2 Nov 2016).
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  9. ^Taeniura lessoni – A New Species of Blue-spotted Stingray,” by Joe Rowlett. Reefs.com, Aug 2016. URL: https://reefs.com/2016/08/05/taeniura-lessoni-new-species-blue-spotted-stingray (accessed on 2 Nov 2016).
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  11. ^ “Blue Spotted Fantail Ray,” by Elasmodiver. The Elasmodiver Shark and Ray Field Guide, n.d. URL: http://www.elasmodiver.com/Blue%20spotted%20fantail%20ray.htm (accessed on 20 Oct 2016).
  12. ^ “10 Stunning Facts About Stingrays,” by Michele Debczak. Mentalfloss, 26 Aug 2015. URL: http://mentalfloss.com/article/67758/10-stunning-facts-about-stingrays (accessed on 8 Nov 2016).
  13. ^ http://www.memidex.com/dimorphism+biology
  14. ^ “5 Things You Never Wondered About Shark Sex,” by Anastacia Darby. Discovery.com, 7 Aug 2015. URL: http://www.discovery.com/tv-shows/shark-week/shark-feed/5-things-you-never-wondered-about-shark-sex/ (accessed on 8 Nov 2016).
  15. ^ Kempster, R. M., E. Garza-Gisholt, C.A. Egeberg, N.S. Hart, O.R. O’Shea & S.P. Collin, 2013. Sexual Dimorphism of the Electrosensory System: A Quantitative Analysis of Nerve Axons in the Dorsal Anterior Lateral Line Nerve of the Blue-Spotted Fantail Stingray (Taeniura lymma). Brain, Behaviour and Evolution, 81: 226-235. DOI: 10.1159/000351700
  16. ^ “Blue-spotted Stingray,” by Ria Tan. Wild Fact Sheets (Wild Singapore), Oct 2013. URL: http://www.wildsingapore.com/wildfacts/vertebrates/fish/dasyatidae/kuhlii.htm (accessed on 7 Nov 2016).
  17. ^ Ferreira, A. S., 2013. Breeding and Juvenile Growth of the Ribbontail Stingray Taeniura lymma at Oceanário de Lisboa [Dissertação] Mestrado em Biologia da Conservação. Univeridade de Lisboa.
  18. ^Taeniura lymma,” by J. Miller. Animal Diversity Web, 2002. URL: http://animaldiversity.org/accounts/Taeniura_lymma/ (accessed on 2 Nov 2016).
  19. ^ Zhang, Y., J. He & K. H. Low, 2012. Parametric Study of an Underwater Finned Propulsor Inspired by Bluespotted Ray. Journal of Bionic Engineering, 9: 166-176.
  20. ^ Rosenberger, L. J. & M. W. Westneat, 1999. Functional Morphology of Undulatory Pectoral Fin Locomotion in the Stingray Taeniura lymma (Chondrichthyes: Dasyatidae). The Journal of Experimental Biology, 202: 3523-3539.
  21. ^ //Forsskål, P. S., 1775. Descriptiones animalium, avium, amphibiorum, piscium, insectorum, vermium; quae in itinere orientali observavit Petrus Forskål. Post mortem auctoris edidit Carsten Niebuhr. Adjuncta est materia medica kahirina atque tabula maris Rubri geographica. Hauniæ: ex officina Mölleri, 1775. URL: http://www.biodiversitylibrary.org/item/18564 (accessed on 7 Oct 2016).
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  23. ^ Fricke, R., 2008. Authorship, Availability and Validity of Fish Names Described by Peter (Pehr) Simon Forsskål and Johann Christian Fabricius in the ‘Descriptiones animalium’ by Carsten Niebuhr in 1775 (Pisces). Stuttgarter Beiträge zur Naturkunde A, Neue Serie 1: 1-76. URL: http://www.naturkundemuseum-bw.de/sites/default/files/publikationen/serie-a/ans01-01fricke.pdf
  24. ^ Lim, K. C., P-E. Lim, V. C. Chong & K-H. Loh, 2015. Molecular and Morphological Analyses Reveal
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