CONTENTS
Flora index
Fauna index
guide to the mangroves of singapore
Crustacea
Peter K L Ng and N Sivasothi (editors)
  Semaphore crabs
Ilyoplax spp.
Family Ocypodidae

Size:
about 0.5-0.8 mm

There are five species of semaphore crabs in Singapore. All are very small crabs and can be easily missed. Crabs communicate in a wide variety of ways. Some are able to stridulate (rubbing granules against a rough surface), making a distinct scraping sound.

Many mangrove species, however, communicate with hand and body signals, much like the days of old before radio when people used a series of coloured flags to get important messages across, like a visual morse code!

Crabs, especially those of the genus Ilyoplax also use semaphore signals in the same manner. Their messages are equally important—signalling territorial rights and a readiness to mate.
close-up of crab signalling
above and below:
Ilyoplax delsmani signalling

close-up of crab signalling

Some males, like those of the White semaphore crab (I. delsmani) even change their body colour to a stunning white which does stand out on a drab mangrove background and then jumping frantically waving their claws. When resting, they turn a dull grey to brown!

Another common species is Tweedies semaphore crab (I. obliqua).

<<Back to crustacea
What is mangrove?
Introduction

The Ecosystem

Abiotic
Biotic

Value
Intro
Products
Indirect uses
Potential uses

About Mangroves
in Singapore

History
Mangroves to visit
Conservation
 
From "A Guide to Mangroves of Singapore", Peter K. L. Ng and N. Sivasothi (editors)
Volume 1: The Ecosystem and Plant Diversity and Volume 2: Animal Diversity
Authors: Kelvin K. P. Lim, Dennis H. Murphy, T. Morgany, N. Sivasothi, Peter K. L. Ng,
B. C. Soong, Hugh T. W. Tan, K. S. Tan & T. K. Tan
BP Guide to Nature Series published by the Singapore Science Centre, sponsored by British Petroleum
2001 Raffles Museum of Biodiversity Research, The National University of Singapore & The Singapore Science Centre