Creature Feature - The Striated Hermit Crab

Andrew Hosie's blog | Created 1 decade ago

The Striated Hermit Crab, Dardanus arrosor (Herbst, 1796); or Lonesome No More!

The striated hermit crab is a very widespread species found in the Mediterranean Sea, west and southern Africa, the Philippines, Japan, New Zealand as well as Australia. This species can be found in waters 30–400 m deep. Dardanus arrosor is one of the largest marine hermit crabs reaching around 15 cm long and belongs to the family of left handed hermits where the left claw is usually the largest. Hermit crabs are generally scavengers, but this one may be able to capture its own prey.

Like other hermit crabs, the striated hermit crab inhabits empty gastropod (snail) shells to protect their soft abdomens. While this hermit will withdraw into the shell when threatened, it certainly isn’t as alone as its name suggests. This species will often have sea anemones attached which act as a further deterrent to potential predators like octopus and large fish. The specimen in the photos not only had the sea anemones (possibly a Calliactis species) but was also host to a diverse array of other animals. This included the small stalked barnacle Poecilasma inequilaterale which will attach to the aperture of the shell and the crab’s limbs where they presumably feed on scraps of food left by the hermit crab. Inside the shell a colony of orange and red amphipods (deepwater cousins of the sandhopper) had found shelter. Also attached to the shell were a number of species of filter-feeding tubeworms (family Serpulidae), and a colony of lace coral (Phylum Bryozoa). The sea anemones had also attracted their own community of dependent animals. A tiny parasitic snail (family Eulimidae) was embedded in one of the anemones. A second species of stalked barnacle, Koleolepas avis, actually attaches to the shell under the anemone. Unlike the first species which has long limbs for catching food drifting on the current, K. avis has short, spiny limbs which they use to snatch and eat the anemone’s tentacles!

The striated hermit crab, Dardanus arrosor – with and without the shell!
Photo by Andrew Hosie
Image copyright of WA Museum

Top row: sea anemone, Calliactis sp, sadly the tentacles are retracted; stalked barnacle, Poecilasma inequilaterale, that was attached to the claw of the hermit crab. Middle row: a male amphipod found inhabiting shell with the hermit crab; the parasitic snail that was embedded in one of the sea anemones. Bottom row: the stalked barnacle Koleolepas avis, found attached to the shell (originally underneath a sea anemone); the pinkish-orange tube of a tubeworm (left) and the colony of lace coral (right).
Photo by Andrew Hosie
Image copyright of WA Museum