Feeding behavior of the Antarctic krill, Euphausia superba DANA. II. Effects of food condition on particle selectivity

摘要

Effects of particle size distribution, total particle concentration, and animal size on selective feeding of the Antarctic krill, Euphausia superba DANA, were studied using natural particles as food. Percent particle retention efficiency calculated from the filtering rate for each particle size spectrum increased abruptly for large size particles. This selective feeding for large particles was apparent regardless of abundance of smaller particles. However, the minimum particle size with 50% retention efficiency (half-retention size) increased with increasing total particle concentration. These results suggest that the feeding of the krill shows intensive selection for large particles when food is abundant, but its feeding is rather passive when food is scarce. This flexible feeding seems to be an adaptive behavior to obtain the energy more effectively in the food scarce ocean.