Animal Species:Semaphore Crab

The Semaphore Crab is the most abundant crab found in mangroves and estuaries, and usually lives among the mangrove roots.

Semaphore Crab on sand

Dr Isobel Bennett © Australian Museum

Standard Common Name

Semaphore Crab

Identification

The Semaphore Crab is easily identified by its mottled purple carapace and eyes on the end of long stalks. Juveniles have orange claws while the claws of adults are purple.

Size range

25 cm

Distribution

The Semaphore Crab is found from Brisbane in Queensland, New South Wales to Port Philip Bay in Victoria, and eastern Tasmania.

Habitat

The Semaphore Crab lives in intertidal mangroves.

Other behaviours and adaptations

The word 'semaphore' means a type of signalling apparatus with moving arms or flags, and refers to the males' habit of standing by their burrows and signalling to other crabs by waving their claws up and down. Exactly what they are signalling is unclear. Perhaps they are trying to grab the attention of females by showing off their large claws, or they may be warning other males to stay out of their territory.

Classification

Species:
cordiformis
Genus:
Heloecius
Subfamily:
Heloecinae
Family:
Ocypodidae
Infraorder:
Brachyura
Suborder:
Pleocyemata
Order:
Decapoda
Superorder:
Eucarida
Class:
Malacostraca
Subphylum:
Crustacea
Phylum:
Arthopoda
Kingdom:
Animalia

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Tags crabs, crustaceans, arthropods, invertebrates, wildlife of sydney, identification,