Energetic costs of amino acids exudation in the interaction between the predatorGammarus pulex L. and the preyAsellus aquations L.

The amphipodGammarus pulex L. displayed aggregative behavior when stimulated by exudates from the isopodAsellus aquaticus L. in laboratory experiments, while the isopod avoided its predator by chemotaxis. Nonvolatile exudates from the amphipod significantly increased the respiration rate of the isopod. Exudation of free amino acids was greatly enhanced when both species were present in the same water, and it was calculated that the increased exudation by the prey was equivalent to a loss of 4-5% of its assimilated energy.