Effects of submersion on the oxygen consumption of the estuarine sandhopper Transorchestia Chiliensis (Milne Edwards, 1840)

Abstract

Oxygen consumption of Transorchestia chiliensis (Milne Edwards) was measured in air and following submersion in sea water of salinity 34%.. In all experimental conditions oxygen consumption increased with dry body weight; the weight exponent in air was 0.76 ( sd ± 0.16) and 0.63 ( sd ± 0.08) in aquatic conditions. At exposure temperatures > 10°C, aquatic rates were consistently below the aerial rate of oxygen consumption, which increased with temperature up to 20°C in winter amphipods and up to 25°C in summer samples. Following submergence, winter-collected amphipods showed maximal oxygen consumption at 10° C and lower oxygen uptake at15°C than at 5°C. For summer amphipods seasonal adjustment in the slope of the R-T curve for aquatic respiration resulted in a plateau of temperature-independent metabolism at temperatures between 5 and 20°C. Oxygen consumption of winter- and summer-collected Transorchestia stored at a constant temperature of 15°C showed a similar relationship between size and oxygen uptake to seasonally collected amphipods. In all acclimated amphipods the oxygen consumption in water remained markedly temperature-dependent up to an exposure temperature of 25°C. Although aerial oxygen consumption of winter-acclimated amphipods approximated the summer values, storage at constant temperatures could not effect completely the changes observed in the aquatic oxygen consumption of seasonally collected amphipods. The ability of Transorchestia to maintain its oxygen uptake at various temperatures following submergence is discussed in relation to the submersion tolerance and its position as a semi-terrestrial member of the supralittoral fringe of New Zealand shores.