Feeding of Naupliar and Adult Carnivorous Cyclopoids (Crustacea : Copepoda)

Abstract

The problem. Little is known about the feeding of naupliar cyclopold copepods, though they are often abundant in the zooplankton.The objective of the current study is to compare feeding of naupliar and adult cyclopoids by testing them on prey types they commonly encounter. Procedure. In-laboratory feeding experiments, using prey difference counts, radiolabeled prey, and predator survivorship, were carried out on a variety of prey types. Predator species included "Cyclops bicuspidatus thomasi", "Mesocyclops edax, and "Cyclops vernalis". Findings: Adult cyclopoids predated on cyclopoid nauplii, "Bosmina", "Asplanchna", and "Paramecium", but not on "Ceriodaphnia", ostracods, "Selenastrum", nor bacteria. One-day old nauplii fed on bacteria mixed with diatomaceous earth and dissolved organics, but not on "Ceriodaphnia", "Bosmina", "Asplanchna", "Paramecium", "Selenastrum", nor free bacteria. The prey difference method worked well for detecting predation of forms larger than 150 ~, while the survivorship method was useful for testing bacteria and algae. The experiment with radiolabeled prey worked poorly. Conclusions. Carnivorous cyclopoid adults and their nauplii differ in food habits, so they do not compete for this resource. Predation by adults is selective against small bodied animals, and is capable of influencing zooplankton community structure, while nauplii have little effect. Cannibalism can regulate cyclopoid populations. Neither adults nor nauplii survive very long on unispecific cultures. Recommendations. Future studies should concentrate on comparing the feeding of cyclopoid stages NI-NIII, NIV-NV and NVI-CIII on bacteria-coated detritus (known size fractions), algae, and dissolved organics: The best methods to use for these foods are predator survivorship, and radiolabeled prey, with modifications in the method of the current study.