 |
|
|
Sand
bubbler crab
Scopimera and Dotilla spp.
Family Dotillidae
updated
Dec 2019
if you
learn only 3 things about them ...
 They are everywhere on the sandy shore at low tide. Don't
step on them!
The tiny sand balls are processed sand. Not excretion
or from burrowing.
They
are related to fiddler crabs. |
|
Where
seen? This tiny ball-shaped crab is often seen on our sandy
shores, just below the high water line. Resembling the little sand
balls that it creates all over the shore at low tide, the crab itself
is often missed. It is also very nervous and disappears instantly
into its burrows at the slightest sign of danger. To spot these crabs,
you will have to wait quietly next to their burrows. Stay low and
avoid casting a shadow over the burrow. In a few minutes, they will
appear. If you stay still, they will go about their amusing business.
Do avoid stepping on sand balls on the shore as you might be stepping
on a little crab!
Features: Body width 1-1.5cm.
Body spherical with eyes on short stalks. These can fold away into
grooves along the bodies when the crabs scurries into its burrow.
Pincers long, flattened and downward-pointing. Males may have larger
and longer claws than females. The crab is generally the same colour
and pattern as sand. It has stiff hairs on the legs which absorb water
from the wet sand. This allows the crab to stay out of water for some
time. |
Chek Jawa, Feb 05 |
Mating
sand bubbler crabs held in the hand.
Chek Jawa, Sep 03. |
Shore
covered with tiny balls of sand
created by busy sand bubblers.
Chek Jawa, Apr 07
|
What does it eat? The sand bubbler
crab eats the thin coating of edible particles on sand grains. Sand
grains are scraped up with the downward pointing pincers and brought
to the mouthparts that sift out these tiny particles. The shifted sand is then discarded in a little ball. As
it processes sand, a little path is scraped out from the burrow entrance.
Little balls of sifted sand is piled up on either side of this path.
Sand patterns: Sand bubbler crabs
are responsible for the delicate patterns of tiny balls on the sandy
shores at low tide. The crabs emerge as soon as the tide recedes.
You can almost tell how long the tide has been out by the patterns
of their sand balls. The more intricate the pattern of sand balls,
the longer the tide has been out. |
Chek Jawa, Mar 05 |
Creating little balls of sand. |
|
| Status and threats: Our sand bubbler
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. Trampling by
careless visitors also have an impact on local populations. |
| Sand
bubbler crabs on Singapore shores |
| Other sightings on Singapore shores |
Coney Island, Jun 20
Photo shared by Richard Kuah on facebook. |
Coney Island, Oct 20
Photo shared by Richard Kuah on facebook. |
|
Chek Jawa, Jul 16
Photo shared by Heng Pei Yan on facebook. |
Chek Jawa, Jun 17
Photo shared by Marcus Ng on facebook. |
Berlayar Creek, Oct 15
Photo shared by Loh Kok Sheng on facebook. |
|
|
Cyrene Reef, Feb 16
Photo shared by Heng Pei Yan on facebook. |
 Terumbu Hantu, Jul 19
Photo shared by Toh Chay Hoon on facebook. |
Beting Bemban Besar, Jun 21
Photo shared by Richard Kuah on facebook. |
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.
- 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.
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
- Edward E.
Ruppert, Richard S. Fox, Robert D. Barnes. 2004.Invertebrate
Zoology
Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963.
|
|
|
