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: 

1.  A Field Guide to Kenyan Mangroves

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

3. A Guide to Seashore Life in Singapore

Acknowledgement:

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

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Behind the Scene of Yummy, Crunchy Soft-Shell Crabs

When crabs grow larger, their shells or carapaces (or exoskeletons) will not be able to accommodate their sizes because their shells will not grow. They must remove the shells and grow a new and bigger ones. This process is known as molting. They molt the exteriors or exoskeletons and have soft coverings for a few days. At this stage, they are now soft-shell crabs until their soft coverings harden. 

In the wild, molted crabs are vulnerable to predators such as stingrays, larger fishes or even fall prey to cannibalism. During this stage, molted crabs will normally find shelter from the predators by hiding in between rocks. That is why it is difficult to catch soft-shell crabs in the net.
Ever wonder how your deep fried crunchy soft-shell crabs made their way to the restaurants and then onto your plate? If you think these soft-shell crabs are caught wild, please allow me to enlighten you.

Indeed that these crustaceans were initially from the wild either caught in the traps or fishing nets.  In the beginning, these crustaceans were juvenile or sub-adult crabs with their hard shells still intacted. Since these crabs were too young to be eaten like ordinary crabs, why not turn them to soft-shell crabs? To do the conversion, these juveniles will have to go through three stages:

Stage 1: TORTURE
Juvenile crabs' walking legs and claws are pulled out. Only the paddling legs remain untouched to allow them to swim around in the enclosure. There is a reason to the legs been pulled out.

   Legless male (left) and female (right) crabs . Note the swimming crabs in the tank.

Stage 2: IMPRISONMENT

These juevys will be in an enclosure tank with sea water and oxygen pump. They will be in there for frequent checks on signs on the areas where the legs were detached. As a juvenile crab begins to grow bigger, the areas of the detached legs will become swollen.

                                  
Note the swollen patches on the legless areas. With such indication, the juvenile crab will be going through molting stage soon, probably between two to five days.

Stage 3: FREEZED TO DEATH
When the juvenile crab has detached its hard shell, it must be removed from the tank within 24 hours. If possible, the earlier the better. If the molted crab takes too long to be removed from the tank, the new exoskeleton will harden and this will lower the quality.  A small translucent plastic bag is ready where the molted crab will be inserted. The tight space in the plastic bag will stop the crab from moving too much. The bag will be folded and then straight into the freezer. The frozen soft-shell crab will be stored in the freezer until more of its comrades follow its fate before being sold to the restaurants.

Harvesting soft-shell crabs is one of the fishery industries being practised in Kuala Gula, Perak. I am sure there must be other way to "harvest" soft-shell crabs in different areas. If anyone have witnessed other methods of process, do share with us.

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The Digger and The Waver. Also the Cutter...?

The digger and the waver I'm refering to is the crustacean that can be found on our mudflats of the mangroves forest. Most crustaceans are diggers. They dig into the mud to make tunnels while aerating the soil at the same time. What about the waver? Ever wonder which crustacean family that does the waving? Fiddler crab (Family: ocypodidae, Genus: uca). Particularly the male that has only one abnormally enlarged claw. A female doesn't have the large one. Depending on the waving action, it may be a display of courtship or even a territory defense.

So, what about being a cutter? If you are curious to find out, click on this link (please be patient with lots of shaking at the beginning and is not a HD movie. I'm aiming to buy a camera with a HD video...soon) :

What you had just watched was a uca vocan cutting a piece of mud to close the burrow when the tide was rising up. Once the burrow closed, the fiddler crab did some patching work so it helped to seal it from water. As a result, the air will be trapped within the tunnel and the fiddler crab will be able to survive till next low tide.

With the right timing, some patience and then a perfect cut. I wonder how he did it without having to measure. Wow, nature is awesome!

I wonder why homosapiens claim themselves as superior and clever...? Where did that come from, huh?

Here is an information posted on how a fiddler eyes work. Click :

http://wildshores.blogspot.com/2009/10/eye-of-fiddler.html

And here is another information on how a female fiddler crab has the ability to defend her territory how-do-girl-fiddler-crabs-defend.

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