The visual pigment of the North Pacific coast chimaeroid fish, Hydrolagus colliei was extracted and analyzed by the method of partial bleaching. The prosthetic group was identified from the difference spectrum of the product formed by bleaching in the presence of NH2OH. The visual pigment in the extract was found to be P4841, a deep-sea type of visual pigment. This is interesting because field studies have indicated that Hydrolagus colliei is not always a deep-water fish. The nature of the visual pigment does not accord with this. It is tentatively concluded, however, that the ecology of this holocephalus fish is insufficiently known to warrant its classification as a strictly surface water inhabitant. In fact, there are reasons to suggest that it is basically a deep-water fish, like other chimaeroids, and that it can migrate vertically, perhaps in response to temperature. © 1969.
