Tachypleus ventral view
These are not
true crabs but belong to a very ancient group presently represented
by only four living species, three of which are found in South East
Their long tails are used mainly to right themselves if they get turned
over, and not as a weapon.
Recently, they have
become important in medical science because a purified extract of their
blood can be used to quickly detect many bacterial toxins, and hence facilitate
eggs are relished by some people but have been reported to be poisonous.
The smaller male normally clings onto the back of the larger female,
following her around just before egg-laying.
They are harmless animals, feeding on worms, bivalves and animal matter.
Two species are common throughout South East Asia - the small and
smooth-tailed Carcinoscorpius rotundicauda (diameter up to
15cm) and the larger triangular and serrated-tailed Tachypleus
gigas (diameter up to 25cm).