Commensalism between a liparid fish (Careproctus sp.) and stone crabs (Lithodidae) photographed in situ using a baited camera

The commensal relationship between a snailfish, tentatively identified as C areproctus sp. (Osteichthyes: Liparidae), and the lithodid crab Paralomis f ormosa (Crustacea: Lithodidae) was photographed in situ using a baited came ra vehicle, deployed at depths of 625-1525 m around Shag Rocks and South Ge orgia in the Southern Ocean. The series of time-lapse photographs taken cle arly showed that the small liparid fish 'hitched rides' on the crabs, presu mably attaching to the dorsal carapace and legs of the crabs by means of th eir ventral sucking disk. Liparid fish of 20-90 mm total length, correspond ing to juveniles and adult sizes, were observed on the crabs and indicate t hat Careproctus sp. is closely associated with P. formosa for the whole of the life cycle of the fish. Such an association may provide the snailfish w ith protection from potential predators as well as a means of transport tow ards food-falls but at no apparent cost to the crabs.