Responses of the crayfish Orconectes virilis to chemical cues depend upon flow conditions.

The responses of individuals of the crayfish Orconectes virilis to the same set of chemical cues were tested under flow (lotic) and non-flow (lentic) conditions. The cues presented to the crayfish were food cues, alarm (=crushed conspecifics) cues, and the combination of food + alarm cues. Crayfish behavior (time in burrows) and posture (lowered posture) were significantly affected by the odor treatment, the flow environment, and an interaction of treatment and environment. While the general patterns of responses to odors (more time spent feeding when food cues were introduced, and more time spent in lowered posture and in burrow when alarm cues were introduced) were qualitatively similar in the two environments, responses were stronger (especially to food odors) in the environment with flow. However, the different strength of these responses seemed not to be related to the directional information provided by the flow but rather was probably the effect of a difference in crayfish behavior between lentic and lotic environments in the control (no added chemical cues). In flow, crayfish spent less time executing feeding movements and more time in the lowered posture and in the burrow than in no-flow conditions.