Fecal pellet production between molts in a cyclopoid copepod: Patterns, individual variability and implications for growth and development

We measured the fecal pellet production rate (FPR) of a cyclopoid copepod (Cyclops cf. sibiricus) individually through the copepodite 5th stage in order to describe the molt-cycle dependent variations in the FPR and the relationship between the FPR and growth and development. Even though individuals of C. cf. sibirucus were kept in the same environmental condition (food quantity, etc.) throughout the development, the FPR was not constant. In general, the FPR was low just after molting into C5, but increased with time and reached the maximum a few days after the molt, and then decreased toward the next molt. More fecal pellets were produced during the earlier part of stage duration time, irrespective of variations in the stage duration time. The total volume of fecal pellets voided through C5 (tCFP) also varied individually with females tending to void more than males. However, neither the weight-specific FPR nor the weight-specific tCFP were different between the sexes. The weight-specific FPR was positively correlated with the individual stage-specific growth rate, suggesting that better growers had a higher ingestion rate, given that the FPR is proportional to the ingestion rate as suggested by other studies.