New Zealand Hermit Crab

Hermit crabs can be identified by the colouration of their antenna and their antennules (a small structure resembling antennae which sits in front of the actual antennae). The hermit crab is approximately the size of a coin and on average 56mm in length, but this is slightly limited by the size of the shells available. Its body is up to 16 millimetres (0.63 in) wide.

Pagurus novizealandiae is widespread on the eastern coast of New Zealand, throughout both North and South Island. It is also found on the Auckland Islands 465 km south-east of New Zealand.

In Australia, the species has been reported in northern and eastern Tasmania from 2013, eastern Victoria, and southern New South Wales. Its identity was confirmed by specimens collected and examined at Museums Victoria. The New Zealand hermit crab is presumed translocated and established.

Hermit crabs are scavengers, they will forage during the night for dead or injured animals and feed off their remains. They can also be found moving about in rock pools during the day. They sometimes partially bury themselves into the sediment and feed on the organic matter, as well as algae, immobile invertebrates and filtered plankton and food particles. They are detritus feeders and eat a fairly broad and assorted diet. The hermit crab has one large powerful pincer/ claw and one small one. The large pincer is strong enough to rip apart the hard outer parts and armour on some of its prey such as tough fish scales, and skeletons so that it can access the soft fleshy parts within and break them into small enough pieces to eat.

Moulting is a vital part of the Pagurus novizealandiae life cycle in order to grow and develop, for the repair of any damaged limbs or other body parts on its abdomen and in the process of preparing for reproduction. Moulting has to occur so that the crab can mature, the hermit crab sheds its exoskeleton, while the crab is still inside of the small, enclosed space of its shell. Underneath is its new soft shell, it must wait until this has hardened so that it can protect its abdomen for when it leaves to find a new shell. The hardening and thickening process only takes a few days. After the moult this results in an increase in the hermit crabs size so it must find a larger shell to house its body. Their shells also just wear out naturally over time, are damaged by predators or become overgrown.