Diving the Helford estuary in Connwall - August 2018

Parasitic anemone (Calliactis parasitica) with hermit crabs
The parasitic anemone, Calliactis parasitica, is sometimes seen on large hermit crabs.

The anemone is in fact not a parasite and the symbiotic relationship between crab and anemone is of mutual benefit. The crab gets protection from certain predators by having the anemone's stinging tentacles on its shell and in turn the anemone gets free transport and scraps of food kicked up by the feeding crab.

This one was photographed in the Helford estuary in Cornwall, which always proves a reliable location to find them.

Nikon D850, Nikkor 60 mm