Snail Fur

Hydractinia echinata

Hydractinia echinata is a colonial marine hydroid that typically forms pinkish-brown patches on the shells of marine gastropods occupied by hermit crabs. These patches can appear brown when the hydroid is dead. The structure consists of a horny mat that is about three millimetres thick, featuring jagged spines that can reach the same height. The hydroid has three types of polyps: feeding polyps that grow up to thirteen millimetres long, male and female reproductive polyps with short tentacles, and specialized defensive stinging polyps with long, coiled threads. This species is particularly common in the northwestern Atlantic, especially on shells occupied by the flat-clawed hermit crab, Eupagurus bernhardus, in sandy substrates along the lower shore. Hydractinia echinata thrives in a range of environments from the Arctic Ocean to the Gulf of Mexico, and it can be found at depths ranging from 0 to 662 metres. However, most occurrences are shallower than 40 metres. It is often found in bay and nearshore areas, where it lives symbiotically with its host gastropods. The reproductive cycle involves the release of planula larvae from the gonozoids, which then seek out moving gastropod shells to colonize. Encountering Snail Fur while diving can be intriguing, as divers may notice its distinctive furry appearance on shells. The hydroid's colonial nature and its association with hermit crabs make it an interesting subject for underwater observation. Conservation status for this species is not evaluated, and it is considered common in its distribution range.