A quantitative description ofMelibefeeding behavior and its modification by prey density

Abstract

The feeding behavior of the nudibranch Melibe leonina is unusual because it lacks a buccal mass. When sufficient prey are present in the water column, rhythmic feeding movements commence. A typical feeding cycle can be divided into 5 phases, beginning with the oral veil opened, and then followed by closing of the oral veil, squeezing and tilting of the head and veil, transfer of food into the mouth, and finally opening of the oral veil. This pattern is then repeated at 0.5–3 cycles/min, depending on the prey concentration. As the feeding rate increases, the duration of each feeding cycle decreases, but the proportion of a cycle occupied by a given phase of the behavior remains the same. When the density of prey are very low, animals will often initiate a feeding cycle and then terminate it just before the tilt and squeeze phase. These data, taken together, suggest that Melibe feeding is a fixed action pattern which is modulated by the availability of prey in the water column.