The feeding response of a marine planktonic copepod to quantity and quality of particles

Abstract

Particles of varying food quality but similar size were offered singly and in mixtures to copepodid Stage V of Eucalanus pileatus to determine the rates at which calanoid copepods ingest naturally occurring particulate matter. The sequence of ingestion rate was: living phytoplankton cells > dead phytoplankton cells > fecal pellets > polystyrene spheres. Cinematographic observations revealed that both long range and short range chemoreception contributed to these differences. Living phytoplankton cells were ingested at rates 1.2 to 3 times higher than similarly-sized non-living food particles. Non-food particles offered alone were not ingested. In mixtures, the rate at which non-food particles were ingested was a function of the feeding rate on food particles. At environmental concentrations the presence of non-food particles does not appear to reduce feeding rates on food particles.

Coprophagy and coprorhexy in the copepods Acartia tonsa and Temora longicornis: clearance rates and feeding behaviour

“…In this study, it is shown that Acartia tonsa and Temora longicornis clear their own fecal pellets at similar rates when offered in a mixture with Thalassiosira weissflogii. Both species are common in coastal waters and a low clearance of fecal pellets may be an adaptation to optimize the intake of high quality food particles in an estuarine environment where non-living particles usually dominate the particulate matter available to copepods (Paffenhöfer & Van Sant 1985). Supporting this, Roman (1984) found that only 10% of a laboratory population of A. tonsa survived 7 d on a detritus diet and that eggs could not be reared to adults on detritus.…”

“…There are some reports with evidence of coprorhexy, coprochaly and coprophagy, and a few estimates of actual pellet grazing rates (Paffenhöfer & Strickland 1970, Paffenhöfer & Knowles 1979, Paffenhöfer & Van Sant 1985, Ayukai & Nishizawa 1986, Lampitt et al 1990, González et al 1994a. The reported grazing rates are, however, highly variable.…”

“…Fecal pellets were visibly opened, macerated and even cut in half during rejection. Eucalanus pileatus females have also been observed to inflict damage to fecal pellets during rejection (Paffenhöfer & Van Sant 1985) and Acartia clausi and Calanus finmarchicus were observed to fragment rather than ingest fecal pellet material (Noji et al 1991).…”

“…Centropages hamatus also lacks a functional response when grazing solely fecal pellets (Lampitt et al 1990), and Eucalanus pileatus similarly has a higher fecal pellet grazing rate in the presence than in the absence of phytoplankton (Table 5, Paffenhöfer & Van Sant 1985). Paffenhöfer & Van Sant (1985) concluded that the feeding rate on non-living food particles was a function of the feeding rate on living food particles and that the increased ingestion of pellets in the presence of T. weissflogii was attributed to an increased filtration activity similar to what we observe here for Acartia tonsa. Calanus helgolandicus nauplii, however, have been observed to have a very different feeding response to fecal pellets and other food particles (Green et al 1992).…”

“…Supporting this, Roman (1984) found that only 10% of a laboratory population of A. tonsa survived 7 d on a detritus diet and that eggs could not be reared to adults on detritus. Other copepod species such as Eucalanus pileatus, Temora stylifera, and Oithona similis may be better adapted to coprophagous feeding since they clear and ingest fecal pellets at high rates (Table 5, Paffenhöfer & Knowles 1979, Paffenhöfer & Van Sant 1985, González et al 1994a. Copepodites of the more oceanic Calanus helgolandicus have been reared to adulthood on a pure diet of fecal pellets in the laboratory (Paffenhöfer & Knowles 1979) and Acartia omorii has been shown to even prefer fecal pellets over Thalassiosira decipiens when offered in a mixture (Ayukai 1987).…”