Inhibition of mating in Aplysia fasciata by food stimuli in the environment, but not by post-ingestion stimuli causing satiation

Aplysia mating is inhibited when animals have steady-state access to food. We examined which stimuli provided by food inhibit mating. Pre-feeding animals to satiation caused a decrease in mating immediately after the meal. This effect could be mimicked by placing food into the water for the length of time of a meal just before the animals were allowed to mate, but not by filling the gut with non-nutritive bulk, which inhibits feeding. The presence of food in the water while animals were allowed to mate caused a stronger inhibition of mating. When food was maintained in the water for 24 h, animals adapted to this stimulus, indicating that the maintained presence of food could not alone account for the inhibition of mating in steady-state conditions of access to food. However, food in the water for 24 h, coupled with an occasional touch of food to the lips while animals had access to mates, caused strong inhibition of mating. We tested the hypothesis that food initiates a state of food arousal, which competes with sexual arousal, and thereby inhibits mating. If this hypothesis is correct, gut fill should facilitate mating, by inhibiting food arousal. However, this effect was not observed. The data support the hypothesis that food stimuli directly inhibit sexual arousal, rather than acting via an excitation of food arousal.