The effects of whole drilling muds on the normal activity of walking leg chemosensory neurons of the lobster, Homarus americanus, were examined using extracellular neurophysiological recording techniques. Exposure of legs for 3–5 min to 10 mg/L drilling mud suspended in seawater altered responses to food odors of 29% of the chemoreceptors examined (data pooled for the two drilling muds tested); similar exposure to 100 mg/L drilling mud resulted in interference with 44% of all receptors studied. The effects of both of these concentrations are statistically significant, although they are not different from each other. Interference was usually manifested as a marked reduction in the number of action potentials in a response. In one preparation, the exposure to drilling mud caused a change in the temporal pattern of the spikes without affecting the total number of spikes. Other chemosensory neurons were excited by 10 mg/L drilling mud itself. However, not all chemoreceptors are inhibited by these drilling muds since responses to feeding stimuli were recorded from the legs of lobsters that had been exposed to drilling mud for 4–8 d before the neurophysiological experiments.Antennular and leg chemoreceptors are important in eliciting normal feeding behavior in lobsters. Although behavioral assays have demonstrated that feeding behavior is altered following exposure to drilling muds and petroleum fractions, there is no conclusive proof for a causal relationship between chemoreceptor interference and behavioral deficits. The two techniques complement each other as pollution detection assays, perhaps reflecting a common interference mechanism.Key words: chemoreception, drilling mud, feeding behavior, lobster, pollution, neurophysiology
