Comparative studies on the physiological ecology of five euryhaline Gammarus species.

Comparative investigations on the physiological capacities of Gammarus locusta (L.), G. oceanicus Segerstråle, G. salinus Spooner, G. zaddachi Sexton and G. duebeni duebeni Liljeborg obtained from German coastal and estuarine areas were carried out under uniform experimental conditions. In order to assess the adaptation of these species to the abiotic conditions of their particular habitats, the following criteria were examined: (a) oxygen consumption as related to temperature, (b) time course of acclimation to a new steady state of metabolic rate following sudden temperature changes, (c) resistance to oxygen deficiency, and (d) resistance to aerial exposure. Considerable interspecific differences were found among the five amphipods studied. G. locusta reveals the highest O uptake rates and longest thermal acclimation periods as well as lowest resistance capacities to oxyten depletion and air exposure. The other species occupy an intermediate position as indicated in the above-cited order, but contrast with G. duebeni which exhibits comparatively high resistance capacities. The significance of the findings obtained is discussed in relation to the environmental requirements of the five crustaceans considered.