Particle selection in the nauplius of Calanus pacificus

Abstract

Food selection by the nauplius of Calanus pacificus is defined as the ability to ingest certain kinds of particles in behavioral preference to others that occur simultaneously in the same environment. Using mixtures of planktonic algae and plastic beads of different or similar sizes, the nauplii strongly selected the algal cells, consuming them almost exclusively, and at similar rates to the controls with only algae. In some cases, however, ingestion rates on the algae were lower than the in the controls, mainly when the mixture was composed of algal cells and plastic beads of smaller sizes able to be captured by the nauplii. Selection of algal particles was also observed when pollen grains or detritus were used instead of the plastic beads. Selection behavior also occurred when mixtures of two algae of different sizes were offered to the nauplii, and it was dependent on the proportion and concentration of both kinds of algae in the mixture. The possible effect of particle production on the observed selective patterns is discussed.