Particle Captures and the Method of Suspension Feeding by Echinoderm Larvae

Motivated by discrepancies between two recent descriptions of the suspension-feeding mechanism employed by echinoderm larvae, I describe particle captures by the larvae of seven species of temperate eastern Pacific echinoderms from four classes. When videotape recordings of free-swimming larvae clearing plastic spheres from suspension were analyzed, two modes of particle capture were observed to operate. The majority of captured spheres were caught at the peripheral ciliated band and then transported to the mouth, often by repeated capture on portions of the band progressively nearer to the mouth. This description is consistent with the ciliary reversal model of suspension feeding described by R. R. Strathmann. A small minority of captured spheres followed broad, curving paths directly into the larval mouth without interception at the ciliated band. These particle paths resemble those described by T. H. J. Gilmour. The videotape recordings also permitted a quantitative comparison of suspension feeding by these larvae. Several aspects of this behavior varied among developmental stages or among types of larvae, including: the distribution of particle captures among different segments of the ciliated band, the number of captures for single particles en route to the mouth, and the frequency of particles lost after initial capture. This variation raises a number of questions regarding the feeding performance of different larval species and the efficacy of these different larvae as elements of a reproductive strategy.