Hydrozoer: Hydractinia monocarpa.

This is a little-known species restricted to Arctic waters. The colonies of H. monocarpa grow preferably on marine snails of the genus Boreotrophon, but unlike other Hydractinia species they seem to be associated with the living snails and are not present when the shell is used by hermit crabs. The combination of their preferred substrate, smooth long pointed spines, and gonozooids without tentacles and with only 1 or 2 gonophores helps to distinguish this species from other Arctic hydractiniids.

Hydractinia monocarpa Allman, 1876
Creative Commons Attribution | Lara Beckmann | Joan J. Soto-Àngel | Aino Hosia | Luis Martell | Universitetsmuseet i Bergen, Universitetet i Bergen
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