Naxia tumida Click to enlarge image
Decorator Crab on rock, Naxia tumida Image: Dr Isobel Bennett
© Australian Museum

Fast Facts

  • Classification
    Species
    tumida
    Genus
    Naxia
    Subfamily
    Majinae
    Family
    Majidae
    Suborder
    Pleocyemata
    Infraorder
    Brachyura
    Order
    Decapoda
    Class
    Malacostraca
    Subphylum
    Crustacea
    Phylum
    Arthopoda
    Kingdom
    Animalia
  • Size Range
    4 cm

Introduction

The Decorator Crab looks like seaweed on the move.

Identification

The Decorator Crab's carapace is covered with hooks to attach algae, seaweed or anything in the environment that will assist in camouflage.

Habitat

The Decorator Crab lives on intertidal rocky shores.

Distribution

The Decorator Crab is found in the temperate waters of Australia in New South Wales, Victoria, Tasmania and Western Australia.

Other behaviours and adaptations

Once a suitable covering is found, the Decorator Crab snips it off with its pincers, coats the end with a special gland secretion that hardens in seawater, and deliberately places it onto its carapace. The crab continues the process until it is sufficiently covered. The algae continue to grow once attached, helping the concealment.

This and other decorator crabs belong to the 'spider crab' family, Majidae. This group includes the largest crab in the world - the Giant Japanese Spider Crab (Macrocheira kaempferi) with a leg span of over 2 m.