Sunday, January 10, 2010

An Ambush Predator In the Mangroves of Langkawi

This aggressive mangrove crab is a fierce predator that would snap its claws at anything it thinks it can eat including your feet! (White, 1847)

Forceps Crab (Epixanthus dentatus) picture taken from http://www.madeinnys.com/mangrove/e_dentatus.htm 

According to Dahdouh-Guebas et al., 1999; this Forceps Crab Epixanthus dentatus (White 1847) is an omnivorous crab but preys mostly on crabs and as well as climbing on mangroves roots (Cannicci et al., 1998). 
A forceps crab can grow only up to the carapace size width of 8cm. It can be identified with scattered orange granules on its carapace that normally hides under driftwood, rocks or debris. Like a male fiddler crab, this forceps crab E.dentatus has an abnormal claw. Unlike the male fiddler crab, the forceps crab E.dentatus has one thin claw and the other is a thick crushing claw. See above picture.
The stout right claw has a special tooth used for opening gastropods or crustaceans. While the other thin claw is like a forceps tool (or like tiny chopsticks) extracting the flesh of its prey. Wow! No wonder E.dentatus is called Forceps Crab.

I can't recall having to encounter a live E.dentatus yet but I was fortunate to find its exoskeleton or carapace. This carapace was found on the mudflat at low tide while I was kayaking in the narrow tributaries of Tanjung Rhu mangroves. From the shape of the carapace,  I believe that this E.dentatus must have gone through the molting process. Aha, it had became a soft-shell crab. I hope to see a live one with its claws ready to strike.



Classification: Biota > Animalia (Kingdom) > Arthropoda (Phylum) > Crustacea (Subphylum) > Malacostraca (Class) > Eumalacostraca (Subclass) > Eucarida (Superorder) > Decapoda (Order) > Pleocyemata (Suborder) > Brachyura (Infraorder) > Eubrachyura (Section) > Heterotremata (Subsection) > Eriphioidea (Superfamily) > Oziidae (Family) > Epixanthus (Genus)


This latest classification was taken from : World Register of Marine Species (WoRMS) 


References: 
2.  A Guide to the Mangroves of Singapore II; published by Singapore Science Center.


Acknowledgement:
1. Thank you to A Field Guide to Kenyan Mangroves website for the picture (hope you don't mind)

2 comments:

  1. Informative. Next time I will be careful when walking near the mangroves in Langkawi. You don't want to get caught on the wrong end of this crab.

    ReplyDelete
  2. Hi Dr Monyet;
    Aiyo... is not easy to look for this unique crab-lo. would be fun to be caught by a mysterious crab like this...hahhahaha...

    Give me a buzz when you are up here. Take you for a walk in the swamp!

    ReplyDelete

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