Abstract
Caprellids were described partially by the setation on the antennae; they are either with or without long, plumose setae on the ventral surface termed "swimming setae." Species with swimming setae have 2 patterns of setal spacing. A logarithmic spacing occurred in those species that could sustain themselves by filter-feeding, while a linear spacing was found in those species needing periphyton (a scraping mode of feeding) for survival. Species without swimming setae are frequent in the plankton and only a 9.0% decrease in swimming rate was measured after removing swimming setae from test animals. Swimming setae have a greater function in food acquisition than in locomotion. Caprella has 49% of the described species in the suborder, excluding Cyamidae, and the species proliferation of this genus is probably related to swimming setae and a new feeding mode for the suborder.