The influence of nutritional status on the feeding behaviour of the field slug, Deroceras reticulatum (Muller)

The field slug, Deroceras reticulatum, a common pest of agricultural and ho rticultural crops, is a generalist herbivore with distinct preferences for particular food items. However, these preferences are not fixed, but are in fluenced by the recent dietary history of the slugs. In particular, slugs t end to select novel food items ('neophilia'). We investigated the basis of such influences, using artificial diets in which protein and carbohydrate c omposition could be controlled and non-nutritional ('secondary') chemicals added as flavours. The slugs showed no general inclination for neophilia ba sed on taste alone. There was a possible learned association between protei n content and taste, but this was weakly expressed. However, the slugs sele cted food items, when given a choice, containing nutrients that were defici ent in earlier diets, even though all the food items contained the same fam iliar secondary taste chemicals. Injections of missing nutrients into the h aemocoel of slugs inhibited such changes in food preference, indicating tha t slugs' feeding preferences are influenced directly by their internal nutr itional status. We suggest that neophilia in D. reticulatum is a physiologi cal response to a nutritional imbalance arising from a suboptimal diet. (C) 2000 The Association for the Study of Animal Behaviour.