STABILITY AND MODULATION OF APLYSIA FEEDING-BEHAVIOR - A PARAMETRIC STUDY

The ingestion of Ulva strips 10 cm long, 1 or 2 cm wide (narrow and wi de ribbon) was automatically recorded and analysed in Aplysia depilans . Graphs expressing ribbon displacements as a function of time were ob tained. They showed a sequence of alternate slow and fast movements (s low and fast ''phase''). The duration of a slow phase was positively c orrelated with the fast phase following it, but not with the one prece ding it. The elementary cycle was characterized in standard conditions by three parameters: 1) length ingested (L); 2) time duration (D); 3) ratio between fast phase duration and whole cycle duration (F). The p arameters remained stable during a sequence. Compared with narrow ribb on ingestion, wide ribbon ingestion led to a rise in D and a fall in L , and resulted in a reduction of the feeding efficiency. D rose in par tially fed animals. With a narrow ribbon, the application of loads exe rting a traction opposing ingestion did not induce significant variati ons in L, D, or F; with a wide ribbon - L and F fell as load increased .