The Responses of the Marine Amphipods Corophium Arenarium and C. Volutator to Gradients and to Choices of Different Oxygen Concentrations

Abstract

A gradient or choice apparatus, based on the ‘fluviarium’ principle and suitable for testing the responses of amphipod crustaceans such as Corophium volutator and C. arenarium to different dissolved oxygen concentrations is described. In a gradual oxygen gradient between 6·99 (100% air-saturated) and 0·17 ml O2/l (2·5% air-saturated) C. arenarium shows a significant preference for the oxygenated water while C. volutator is indifferent. The difference between the species is emphasized in experiments with a choice between the above-mentioned oxygen concentrations. Furthermore, in this situation C. volutator shows a greater preference for the deoxygenated water. The response in the choice situation becomes more definite after a period of time. Both Corophium species react immediately at the abrupt oxygen gradient in the choice chamber; C. arenarium is the more sensitive. It is concluded that C. arenarium responds to the dissolved oxygen gradient through an orthokinetic mechanism and that the difference between the two species of Corophium may be correlated with a difference in the oxygen regimes of their respective habitats.