Pharyngeal movements during feeding sequences in Navanax inermis: a cinematographic analysis

Pharyngeal movements during feeding in Navanax inermis were filmed and correlated with known neural activity controlling the pharynx. Seven distinct components of feeding were identified. Occurrence of a component was in some cases fixed, in that once initiated the act went to completion, and in other cases reflex, in that tonic stimulus control was needed for the act to be maintained. As few as 2 or as many as 7 different motor acts could occur in a feeding sequence. The specific acts which make up a sequence were dependent upon the nature of the prey stimuli that elicited feeding: qualitatively as well as quantitatively different feeding sequences were elicited by prey of differing sizes or by prey which was withdrawn from Navanax at different stages in a movement. The data indicate that the sequence of pharyngeal movements is not preprogrammed, but rather the sequence is appropriate to a specific type of prey. Flexibility in fitting a feeding sequence to the prey that elicits the sequence is achieved by combining in different ways a limited number of specific, fairly stereotyped motor acts.