Comparative grazing experiments of various developmental stages and sexes of the inshore marine copepod Pseudodiaptomus marinus on naturally occurring particles were carried out. The feeding behavior was similar between both sexes of the adult, but different between developmental stages. The adult females were capable of consuming almost all particles from 2.8 to 63.3 μm diameter, showing selectivity for larger particles (ca. 50 μm) where the peak of particle concentration occurred. The nauplii consumed mainly smaller particles (<30 μm). The consumption by copepodites was intermediate between that of the nauplii and adult females, since they fed upon both smaller and larger particles. Such intraspecific differences of grazing behavior may lead to the effective utilization of heterogeneous natural food resources.
The ingestion rates of the adult females increased linearly with the increase of particle concentrations, without indications of the threshold nor saturation response. The amount of ingested carbon rarely met the requirement for potential egg production which was observed for the wild population. Thus, it was surmised that the adult females could ingest sufficient food deposited on the sea-bottom during a daytime epibenthic phase to attain predicted egg production
