PHYSIOLOGY OF TWO SPECIES OF DEEP-WATER CRABS, CHACEON FENNERI AND C. QUINQUEDENS: GILL MORPHOLOGY, AND HEMOLYMPH IONIC AND NITROGEN CONCENTRATIONS

ABSTRACT The general physiology of two species of deep-water crabs, Chaceon fenneri and C. quinquedens, found in thermally stable environments at moderate depths, was investigated. Structurefunction relationships of the gills indicate animals that are typical of environments characterized by high and stable salinity. The gill lamellae are composed entirely of respiratory epithelium; no ion-transporting "chloride cells" were observed. Carbonic anhydrase, a marker enzyme for ion transport in the gill, was present in very low levels of activity, and blood osmotic and ionic concentrations were not different from ambient at salinities of either 35 or 20 ppt. Animals failed to survive in salinities lower than 20 ppt. Oxygen uptake values were typical of coldwater, benthic species, regardless of habitat depth. Chaceon quinquedens appears to have both a higher rate of oxidative metabolism and a higher rate of protein metabolism than C. fenneri, which may be indicative of a higher rate of growth. Both species, however, appear to be physiologically similar to stenohaline marine decapods from cold, shallow-water habitats.