Hermit crabs

Malta's big hermit crabs are the red hermit crab (Dardanus calidus) and the greater hermit crab (Dardanus arrosor). Both are startlingly colourful once you light them: scarlet to orange-red legs and claws, often furred with fine hair, and stalked eyes with green or blue highlights. The left claw is much the larger and works as a door, plugging the shell mouth when the animal pulls in. Body length reaches about 10 to 12 cm, and they carry correspondingly large gastropod shells, usually old tun or triton shells. Two much smaller species also turn up: the dark, red-legged Clibanarius erythropus in shallow pools and the tiny Calcinus tubularis under stones.

The big ones live on rocky reef, mixed sand and rubble, and the edges of Posidonia meadows, from a couple of metres to 100 m, with most sightings between 5 and 40 m. They are scavengers, working over anything dead or rotting, and they are permanently busy, so a hermit crab is one of the easier animals to watch behaving naturally.

The detail worth knowing is the anemone. Dardanus commonly carries one or more Calliactis parasitica anemones cemented to its shell. The anemone's stinging tentacles deter octopus, and the crab gets the scraps thrown up by the crab's feeding. When it changes shell it carefully prises the anemones off the old one and presses them onto the new.