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Mud
crab
Scylla sp.
Family Portunidae
updated
Oct 10
Where
seen? This enormous crabs is among our favourite seafood.
It is seldom seen and is usually hidden in its burrow in the mangroves.
Sometimes, large individuals are seen in other habitats. These are
likely to be fully grown adults that were taken from seafood markets
and released as part of religious rituals, unfortunately, usually
in unsuitable habitats.
Features: Body width to about
20cm. Mud crabs belong to the same family as swimming crabs and their
last pair of legs are paddle-shaped. But because they are such large,
heavy crabs, they don't use these legs to swim. Instead, the legs
are used like spades to burrow with.
Body somewhat fan-shaped with 9 spines on the sides but the last tooth
is not enlarged as it is in flower crabs.
Unlike flower crabs, mud crabs are able to stay out of water for some
time. They come in various colours ranging from dark green (mostly
those from mangroves) to bluish green (those found in open waters).
What does it eat? This crab is
a predator and will eat any animal that it can catch. It appears to
prefer snails and clams.
Role
in the ecosystem: As predators, these crabs control the
population of their prey and thus the natural balance in the ecosystem.
In turn, they are eaten by animals higher up in the food chain.
Human uses: These crabs are edible
and a favourite dish for many Singaporeans. They are traditionally
caught by hooking them out of their burrows with long iron rods.
There are three species of mud crabs found in Singapore.
The Green mud crab (S. paramamosain) body width to about 15cm,
the Orange mud crab (S. olivacea) to about 18cm, and Purple
mud crab (S. tanquebarica) to about 20cm.
The Mud crab we often eat at restaurants are actually from the Giant
mud crab (Scylla serrata) which can grow to about 28cm. These
come from Sri Lanka (thus sometimes also called the Sri Lankan crab).
This crab is not found in Singapore.
Status and threats: Our mud crabs
are not listed among the threatened animals of Singapore.
However, like other creatures of the intertidal zone, they are affected
by human activities such as reclamation and pollution. Over-collection
can also have an impact on local populations.
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It is better known as Chilli crab!

Changi, Jul 07


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Mud
crabs on Singapore shores

Dead specimen
Changi, May 06
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Links
References
- Ng, Peter
K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema
Brachyurorum: Part 1. An annotated checklist of extant Brachyuran
crabs of the world. The Raffles Bulletin of Zoology. Supplement
No. 17, 31 Jan 2008. 286 pp. (Online
PDF on the Raffles Bulletin of Zoology website).
- Lim, S.,
P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life
and Times of Labrador Beach. Division of Biology, School of
Science, Nanyang Technological University & Department of Zoology,
the National University of Singapore. 160 pp.
- Ng, P. K.
L. & Y. C. Wee, 1994. The
Singapore Red Data Book: Threatened Plants and Animals of Singapore
.
The Nature Society (Singapore), Singapore. 343 pp.
- Jones Diana
S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of
Australian Waters. Reed New Holland. 224 pp.
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