Heloecius cordiformis Click to enlarge image
Semaphore Crab, Heloecius cordiformis Image: Dr Isobel Bennett
© Australian Museum

Fast Facts

  • Classification
    Species
    cordiformis
    Genus
    Heloecius
    Subfamily
    Heloecinae
    Family
    Ocypodidae
    Suborder
    Pleocyemata
    Infraorder
    Brachyura
    Order
    Decapoda
    Superorder
    Eucarida
    Class
    Malacostraca
    Subphylum
    Crustacea
    Phylum
    Arthopoda
    Kingdom
    Animalia
  • Size Range
    25 cm

Introduction

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

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.

Habitat

The Semaphore Crab lives in intertidal mangroves.

Distribution

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

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.