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episesarma singaporense; brachyura
Singapore vinegar crab
One of the most common crabs in the
plays an important role in its habitat. It primarily feeds on leaves, and lives within burrows and on trees (Sivasothi, 2000). Like other tree-climbing crabs,
possesses a carapace (shell) with reticulated (net-like) patterns on the area next to its mouthparts (Tan et al., 1988). However, the Singapore vinegar crab is characterised by its claws that are completely red.
Table of Contents
Links to other websites:
Other names people have used in the past
for more information)
How the crab got its name
This crab species was first discovered in Singapore; hence it was named in reference to the location of first collection (i.e. Singapore).
How to tell
apart from other crabs in the mangroves
In Singapore, there are currently
described species of
These three species can be
differentiated from other mangrove crabs
by the following features:
1) The quadrangular (squarish) and dorsally flattened (flat on top) carapace (shell).
2) High carapace (shell) and sharply deflexed (angled downwards) front ("face").
3) Reticulated (net-like) patterns with fine setae (hairs) on the pterygostomial regions (area around mouth-parts).
4) On the palm of the male chela (claw), there are small raised teeth (sharp bumps) that run from the
(towards the body) to the
end (away from the body).
Among these three species,
from the rest by the
colour of their chelae
claws is completely
(with the fingers a darker shade than the palm); while the other two species have white and purple colourations.
, like other species from the genus, feeds mainly on foliage (Sivasothi et al., 1993; Sivasothi, 2000). However, it has also been known to feed on other plant material (leaf-litter, flowers and propagules) and scavenge on meat (Sivasothi et al., 1993; Lim et al., 1999).
, inhabits estuarine conditions their entire adult lives. Gravid females produce numerous small eggs (Soh, 1969), that develop into larvae much like other sesarmine crabs. These stages include four zoea and one megalopa stage; and morphological differences can be used in identification (see description
). These larval stages eventually develop into adults of carapace width 30-38 mm (see description
). Reproduction and spawning cycles of
have yet to be determined.
The crabs normally climb trees to avoid aquatic predators like fishes. However, when threatened by other animals while on the tree, the crabs leap into the water, and climb another tree thereafter (Sivasothi, 2000).
are mainly found in
(Sivasothi, 2000). They tend to live within burrows excavated at the roots of mangrove trees and
) mounds, only climbing up trees during high tide events. Additionally, they tend to be found in greater numbers at inland mound systems (Sivasothi, 2000).
Mangroves of South-east Asia— E.g. Brunei Darussalam, Indonesia, Malaysia, Singapore and Thailand.
crabs are not evaluated by IUCN red-list assessment,
currently appears to be abundant in the mangroves of Singapore.However, while they are unlikely to face threats from pollution and eutrophication (Lee, 1998), they are susceptible to habitat loss due to the fact that their range is restricted to the mangroves (Sivasothi, 2000). This, coupled with the fact that mangroves of South-east Asia are facing increasing destruction (Alongi, 2002), indicates that habitat loss could present a potential threat to these crabs in the future.
Like other crabs from the family Sesarmidae,
plays a vital role in nutrient cycling. Their consumption of leaves and plant propagules (Sivasothi, 2000) helps breakdown vegetative materials, increasing the speed of recycling of mangrove leaf-litter (Lee, 1997, 1998). Moreover, their burrowing activities can alter the substrate topography and biochemistry as well (Kristensen, 2000).
, like other Sesarmine crabs, is known to be consumed as food in several cultures. The Teochews preserve the crabs in black vinegar, then cook and eat them with porridge (left). Additionally, the Thais and Cambodians also preserve the crabs in salt, eating it with variations of a papaya salad (Lim et al., 1999).
Relative position of
in higher order groupings
(This allows one to identify biological groupings of the crab. Note that taxon ranks were intentionally omitted due to subjectivity in namings.)
- Animalia Linnaeus, 1758
- Arthropoda Latreille, 1829
-Crustacea Brünnich, 1772
-Malacostraca Latreille, 1802
-Decapoda Latreille, 1802
-Brachyura Linnaeus, 1758
-Grapsidae Macleay, 1838
-Sesarmidae Dana 1851
de Man 1895
Relative (phylogenetic) position of
among other crabs.
(This figure only highlights the position of
amongst other members of the subfamily Sesarmidae and family Grapsidae)
This figure shows that
are monophyletic, thus providing support for their genus grouping.
The history of how the name of the crab changed from
(This history allows for one to easily establish which particular species past researchers were referring to)
Originally described by
, this species was later reassigned to genus
Serene & Soh
(1970), due to confusion regarding the original genus (
Tan & Ng, 1994
was later determined to be synonymous with
with the latter having nomen nudum (Holthuis, 1978; Tan & Ng, 1994). Hence,
is currently used as the genus name and the tense of the species name (
) was altered to
to accommodate the genus
Where the original specimens (that were first described) are stored in
(The type provides a reference point for when a species was first named. This is often important for determining the correct application of a species name in taxonomic research)
, syntypes (two specimens that were listed in description of species) were used, and a holotype was not designated.
These syntypes (one male and one female) were collected by Tweedie in June 1935 (Tweedie, 1936). Specimens were deposited and are currently stored in the Raffles Museum of Biodiversity Research (Singapore).
Morphological features of
that can be used for identification
(Both adult and larval forms have been described)
Carapace— High with sharply deflexed front (Soh,1969). Free edge of which is less sinuous than other allied species (Tweedie, 1936). Carapace is almost quadrangular and dorsally flattened (Serene & Soh, 1970), with width of 30-38 mm (Tweedie, 1940). Epibranchial teeth are present along the lateral margins, behind the external orbital teeth,the latter of which is typically acute (Soh, 1969).
Pterygostomial regions— Pterygostomial regions around mouth has a reticulate pattern with numerous setae.
Chela— Colouration of entire chela is entirely red (with both dactylus and pollex of a deeper shade) (Tweedie, 1936). Few coarse teeth are located on the pectinated ridge of the palm of males; females do not possess the pectinated ridge, but rather a raised line of granules (Tweedie, 1936). The tubercles on the upper margin of dactylus typically range from 36-46 in males and roughly 30 in females (Tweedie, 1936, 1940). The number of tubercles on dactylus normally increases with age and size of specimens (Tweedie, 1940). In males, tubercles are typically small, transverse and parallel-sided in the proximal end, but larger and more triangular-shaped at the distal end (Tweedie, 1936). The length of tubercles (measured along axis of dactylus) increases gradually from the proximal end to the distal end, with the latter being more than twice as long as the former (Tweedie, 1940). In females, tubercles only occupy the proximal two-thirds of the dactylus, and are typically smaller and less developed than males (Tweedie, 1936).
Ambulatory legs— Posterior border of meri pereopods (2nd-5th) lack denticulations. Merus width of third pereopod are generally equal to or greater than half its length (Soh, 1969).
Pleopod— First male pleopods is very slightly expanded at the tip, and quite distinct from other allied species (Tweedie, 1940)
There are morphological differences between the different larval stages, namely the four zoeal and single megalopa stage. These differences are determined by the number of setae on the various body parts. Teo (unpublished) described these stages and determined that they can be used for differentiating between various species of sesarmine crabs. However, as the author is currently in the process of publishing his work, these stages would not be displayed on the website presently.
Links to other websites:
World Register of Marine Species (WoRMS)
Guide to Mangroves of Singapore
Alongi, D. (2002) Present state and future of the world's mangrove forests.
De Man, J. (1895) Bericht über die von Herrn Schiffscapitän Storm zu Atjeh, an den westlichen Küsten von Malakka, Borneo und Celebes sowie in der Java-See gesammelten Decapoden und Stomatopoden. Zweiter Theil.
Zoologische Jahrbücher. Abteilung für Systematik, Geographie und Biologie der Thiere
Fratini, S., Vannini, M. & Cannicci, S. (2005) Tree-climbing mangrove crabs: a case of convergent evolution.
Holthuis, L. (1978) A Collection of Decapod Crustacea From Sumba, Lesser Sunda Islands, Indonesia.
Kristensen, E. (2008) Mangrove Crabs as Ecosystem Engineers; with Emphasis on Sediment Processes.
Journal of Sea Research
Lee, S. (1997) Potential Trophic Importance of the Faecal Material of the Mangrove Sesarmine Crab Sesarma Messa.
Marine Ecology-Progress Series
Lee, S. (1998) Ecological Role of Grapsid Crabs in Mangrove Ecosystems: a Review.
Marine and Freshwater Research
Lim, K., Murphy, D., Sivasothi, N., Ng, P.K.L. & Tan, K. (1999)
A guide to the mangroves of Singapore II
(PKL Ng and N Sivasothi, Eds.). Singapore Science Centre, Singapore.
Schubart, C.D., Cannicci, S., Vannini, M. & Fratini, S. (2006) Molecular phylogeny of grapsoid crabs (Decapoda, Brachyura) and allies based on two mitochondrial genes and a proposal for refraining from current superfamily classification.
Journal of Zoological Systematics and Evolutionary Research
Schubart, C.D., Liu, H.-C. & Ng, P.K.L. (2009) Revision of Selatium Serene & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), with Description of a New Genus and Two New Species.
Serene, R. & Soh, C.L. (1970) New Indo-Pacific genera allied to Sesarma Say 1817 (Brachyura, Decapoda, Crustacea).
Sivasothi, N., Murphy, D.H. & Ng, P.K.L. (1993). Tree climbing and herbivory of crabs in the Singapore mangroves. In: A. Sasekumar (ed.), Mangrove fisheries and connections. Proceedings of the ASEAN-Australian Marine Science Project: Living Coastal Resources Workshop: 220-237. (ASEAN-Australia Marine Science Project, Malaysia).
Sivasothi, N. (2000) Niche preferences of tree-climbing crabs in Singapore mangroves.
Soh, C.L. (1969)
Studies on some biological aspects of Sesarma (Decapoda, Brachyura) of Singapore
. Thesis (M.Sc.) - Dept. of Zoology, University of Singapore, 1970.
Teo, G. Y.J. (2011)
Complete morphology of the larvae of Singapore’s mangrove tree-climbing crabs (Decapoda: Brachyura: Sesarmidae)
. Thesis (Honors)- Dept. of Biological Science, National University of Singapore (2011).
Tan, C.G.S. & Ng, P.K.L. (1994) An Annotated Checklist of Mangrove Brachyuran Crabs From Malaysia and Singapore.
Tweedie, M. (1936) On the Crabs of the Family Grapsidae in the Collection of the Raffles Museum.
The Bulletin of the Raffles Museum
Tweedie, M. (1940) New and interesting Malaysian species of Sesarma and Utica (Crustacea Brachyura).
Bulletin of the Raffles Museum
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