Gill tissue respiration in two species of crabs, Hemigrapsus nudus and Hemigrapsus oregonensis

Oxygen consumption of gill tissue of Hemigrapsus nudus and H. oregonensis has been measured at four levels of experimental salinity (35%, 75%, 100%, and 125% sea water), three levels of experimental temperature (5°, 12,5° and 20°C) in all combinations for both winter and summer animals. Summer animals of both species were found to have higher weight-specific oxygen consumption than winter animals when measured at the average summer (20°C, 35% sea water) and winter (5°C, 75% sea water) field conditions. At other experimental conditions respiration rates of summer-adapted animals were found to be higher for the majority of conditions, but there were examples of equal seasonal rates and examples of winter rates exceeding those obtained from summer animals. Winter animals were found to be less temperature-dependent than summer animals. No laboratory compensation to temperature of biological significance could be found in either species. Hemigrapsus nudus demonstrated a higher weight-specific oxygen consumption than H. oregonensis. Both species showed with minor differences, similar responses to the various factors investigated. The weight-specific oxygen consumption data present indirect evidence which indicate that the gills of both species are involved in regulating blood ions. The indications are that regulation of ions by the gills is more pronounced in summer than in winter. The regression coefficient of weight-specific oxygen consumption as a function of whole body weight was found to have a value of -0.169. This value was similar for both species and not affected by experimental conditions. The differences in physiological response between species indicate that the less variable Hemigrapsus nudus may be a select population which has migrated into this area from the outer coast and that H. oregonensis may be indigenous to this locality.Science, Faculty ofZoology, Department ofGraduat