Hermit crab: a very social hermit

A crab who squats in other houses with flatmates and secret friends.

This hermit crab (Diacanthurus rubricatus) lives in an abandoned helmet shell that fits snugly, but despite its name, it shares its whare with others.

Hermit crab, Diacanthurus rubricatus, from NIWA Station 0254 off Kaikoura, depth 80-100 metres, [date unknown]. Photo by Ken Grange, courtesy of NIWA

House-sharing is good for the whole group. The smaller animals get scraps of the crab’s kai. Anemones like the Anthothoe albocincta (white stripe sea anemone) in the next image sting predators and protects the community.

Hermit crab with white stripe anemones on its shell. Photo by Rob Wilson/Ghost Fishing NZ

The hermit crab is super adaptable – it can live between 15 metres and 2 kilometres deep. Most animals that can live in deep water spread to many parts of the world, but this crab lives only around Aotearoa.

But wait, there’s more: the crab’s secret friend

A tiny copepod also lives with hermit crabs and spends its whole life in the tip of the hermit crab’s shell. Copepods are a type of crustacean, like shrimp and crabs.

Hermit crab copepod, Kioloaria tapui, 2000. Photo by Jean-Claude Stahl. Te Papa (TMP032398)

The species, Kioloaria tapui, was discovered in 1982 by Te Papa scientists. It was named ‘tapui’, or ‘close friend’, because it’s always found with hermit crabs and their shells.

This page is part of Te Ika Whenua | Unique NZ section of Te Taiao | Nature at Te Papa.