The Crustacea

Nippers and claws

Red rock crab      Common swimming crab      Hermit crab      Pink barnacle      Common crayfish

Crustacea have an external, jointed skeleton which covers the body and limbs like a suit of armour. They belong to the great group of joint-legged animals (anthropods).

Red Rock Crabred rock crab

(Plagusia chabrus)

Habitat: Lives in cracks of rocks along exposed coasts.

Identification: A large red crab which grows to about 8 cm across the back.

General: Becomes active at night and may venture out onto exposed rock platforms at dusk. It can run swiftly and clings to the rock surface to prevent being washed away by the waves.

Common Swimming Crab

Other Names: Paddle crab. (Ovalipes catharus)

Habitat: Common in sandy areas.

Identification: A large crab which grows to about 9 cm across the back. The last joint across the last pair of legs is flattened to form a paddle.

General: Uses its paddles either for swimming or digging backwards into the sand. When in the sand it will remain hidden with only the eyes and antennae visible.


Hermit Crabhermit

(Pagurus novaezelandiae)

Habitat: Lives in an empty univalve shell.

Identification: Uses a shell to protect its soft, twisted abdomen. One nipper is usually larger than the other.

General: Protects itself by pulling back into the shell and folding the larger claw across the opening. As it grows, it discards the smaller shell and moves into a slightly larger one.

Pink Barnacle

(Balanus decorus)

Habitat: Lives at or below low tide level and is often attached to shells, particularly dead ones inhabited by hermit crabs.

Identification: Pink limy shell conceals the crustacean inside. Grows to about 4 cm across.

General: Only the larval stage can move about. Once the barnacle settles down and builds its first shell, it remains fixed for life. Fixed, in fact by its head so, to feed, it waves its curved feet through the water and passes anything collected inwards to the mouth. Each barnacle has both male and female sex organs.


Common Crayfishcrayfish

Other Names: Spiny or red crayfish. (Jasus edwardsii)

Habitat: Rocks and crevices.

Identification: Colour a mottled deep purplish-red and orange. Has rows of depressions across the tail segment.

General: Smaller than the smoothtail (packhorse) crayfish found further north. Female has pairs of pleopods (flappy things) under the tail and has small pincers on the rear pair of legs. The male has no extra pincers and only a single line of pleopods beneath each side of the tail.


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