A PROPOSED DUAL ROLE OF ODOR IN FORAGING BY THE CALIFORNIA SPINY LOBSTER, PANULIRUS INTERRUPTUS (RANDALL)

¹ Department of Biological Sciences and the Marine Sciences Institute, University of California, Santa Barbara, California 93106

A dual influence of odor on foraging is proposed for Panulirus interruptus, on the basis of laboratory and field tests using abalone muscle effluence as a stimulant. Food search consisted of three major components: detection (increased antennule flicking), locomotion, and non-locomotor probing by pereiopod dactyls. Detection occurred at lower concentrations (l0^-8 to 10^-10 g/l) and was initiated before probing and locomotion in laboratory tests. Probing occurred at concentrations 10^-6 g/l and was initiated before locomotion. Locomotion was limited to higher concentrations ( 10^-4 g/l) and its induction frequently followed introduction of an effective chemical stimulus by 60 s or longer. The response hierarchy in Panulirus indicates that concentrated chemical stimuli may initiate only local searches for food.

Traps were baited with abalone muscle for field experiments. Effective effluent concentrations in immediate trap environments were estimated by a three-dimensional Fickian diffusion model. The minimum concentration attracting lobsters was estimated to be nearly identical to the laboratory-determined threshold for detection, 4-6 log units lower than the threshold for induction of locomotion. Lobsters were captured in traps primarily at night, the period of greatest normal, endogenously initiated activity. Consequently, low concentrations may act by modifying behavior of animals already aroused, rather than by initiating foraging or feeding from the quiescent state.

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