Effects of Temperature, Pressure, and Oxygen Concentration on the Oxygen Consumption Rate of the Hydrothermal Vent Crab Bythograea thermydron (Brachyura)

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Abstract
Oxygen consumption rates of the brachyuran crab, Bythograea thermydron, from the Galapagos hydrothermal vents were measured at temperatures of 2, 8, 12, 18, and 25 C; pressures of 272, 136, and 1 atm; and varying oxygen concentrations. The oxygen consumption rates were comparable to those of both shallow-living and deep-sea benthic decapods. Temperature had a minimal effect on oxygen consumption over the range of 8-18 C, and its effects increased at temperatures outside this range. Decompression of the crabs from their environmental pressure (272 atm) to 136 atm had no significant effect on oxygen consumption. Further decompression to 1 atm led to increased oxygen consumption. Vent crabs are able to regulate their rate of oxygen consumption down to an oxygen partial pressure of 13 mm Hg; this is unaffected by temperatures from 2 to 25 C and pressures from 1 to 272 atm. The crabs have an anaerobic capability exceeding 12 h. The results provide insight into the relative role of ecological factors (predation, competition) as opposed to environmental conditions (temperature, pressure, food) in selecting the characteristics of deep-sea species. The importance of temperature, pressure, and food availability in influencing metabolic rates in the deep sea are discussed. Habits and physiological capabilities of the crabs in the unusual vent environment are suggested on the basis of the crabs' physiological tolerances.