 |
|
| crabs text index | photo index |
| Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans > Superfamily Ocypodoidea |
| Soldier
crab Dotilla sp. Family Dotillidae updated Aug 10
Where seen? This amusing ball-shaped crab is sometimes seen on natural sandy bars. While the shy crab itself is seldom seen (as it hides as soon as it senses footsteps far away), the balls of sand that it leaves on the shore at low tide indicate where it is active. To spot one, you will have to wait quietly next to a burrow. Stay low and avoid casting a shadow over the burrow. In a few minutes, it and its neighbours will appear. If you stay still, they will go about their amusing business Features: Body width to about 1.5cm. Body spherical, greenish eyes on short thick reddish stalks, pincers long, slender and downward pointing. The crab is well adapted for life out of water: it can absorb air through special parts of its legs which are thinner. It also absorbs water from the sand through silky hairs on the abdomen. Unlike most crabs, the soldier crab can run forwards as well as sideways. And it can move very fast indeed! Dotilla wichmani is smaller (body width up to 1cm) and prefers sandier areas not wandering far from its hole. Dotilla myctiroides is larger (body width up to 1.5cm) and is found in muddier areas often moving around in large groups at low tide. This habit of 'trooping' in numbers gave these crabs their common name. Sometimes mistaken for the sand bubbler crab. The soldier crab is larger and has longer, thinner pincers. What does it eat? The soldier crab eats the thin coating of detritus on sand grains. Sand grains are scraped up with the downward pointing pincers and brought to the mouthparts that then sift out any tiny food particles. The shifted sand is then discarded in a little ball. A soldier crab leaves larger sand balls in untidy heaps, while the sand bubbler crab is much tidier. Status and threats: One of our soldier crab species (Dotilla myctiroides) is listed among the threatened animals of Singapore due to loss of our natural beaches. While somewhat common on Chek Jawa, they are not commonly seen elsewhere in Singapore. Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors can also have an impact on local populations. |
 Chek Jawa, Nov 04   Typical burrow with small and big sand balls around the opening. Chek Jawa, Feb 06 |
They are everywhere on the sandy shore at low tide. Don't
step on them!
 Kusu Island, Feb 07 |
 Creating the sand ball. |
 |
Soldier crabs on Singapore shores
 Chek Jawa, Jun 07 |
 Sealing itself underground ... |
 ... before the tide comes back in. |
Links
References
|
.
The Nature Society (Singapore), Singapore. 343 pp.|
|