FUNCTIONAL CONSEQUENCES OF TROPHIC SPECIALIZATION IN PUFFERFISHES

1. Trophic breadth may be correlated with behavioural and functional v ersatility or flexibility (Liem 1984), such that species with limited diets would be predicted to be less versatile or flexible in their fee ding capabilities than would trophic generalists. The relationship was examined between the trophic breadth of a species and the degree to w hich muscle activity is influenced by prey type in two species of puff erfishes: Chilomycterus schoepfi, a specialist on hard-shelled prey, a nd Sphoeroides nephalus, a generalist predator. It was predicted that the specialist would show a decreased ability to alter its motor patte rn in response to prey type and an increased amount of motor-pattern v ariability when feeding on different prey. 2. Electromyographic record ings of five feeding muscles were made from five individuals per speci es feeding on four prey types that differed in their hardness and esca pe abilities. Muscle-activity duration, relative onset and integrated rectified area were analysed for prey capture and manipulation behavio urs for each prey type, 3. Prey-type effects on mean motor-pattern var iables for capture were limited to one of 14 variables in each species . Prey effects on buccal manipulation were not significant for any of the 14 variables for C. schoepfi, but S. nephalus exhibited prey effec ts for seven out of 14 variables. No differences in motor-pattern vari ation were found for the strike, but-species differed significantly in overall motor-pattern variability during buccal manipulation; C. scho epfi, the dietary specialist, exhibited greater motor variability than S. nephalus, the dietary generalist. 4. The results therefore support a direct relationship between the trophic breadth of a species and it s functional versatility for buccal manipulation. In contrast, prey ca pture was a relatively stereotyped behaviour for both species, as few prey-type effects were found.