Genetic variation in Ophiomusium lymani (Echinodermata) populations in the deep sea

Gene and genotype frequencies in a polymorphic esterase isoenzyme system were measured in collections of the brittle-star Ophiomusium lymani taken at approximately 2000 meters off the coast of North Carolina. Frequencies varied with the depth of the collections but not with their geographical location along the contours. An excess of a homozygote above Hardy-Weinberg expectation was observed in the deeper samples.