The influence of food concentration and container volume on life history parameters of Diaptomus dorsalis Marsh from subtropical Florida

Abstract

IntroductionTwo experiments were conducted with a subtropical calanoid, Diaptomus dorsalis Marsh 1907, to determine the influence of food concentration and the volume of medium per copepod (one copepod in each of several containers of different volumes) on post-embryonic development rates, adult body size, clutch size, survivorship and sex ratio. Low concentrations of food (Chlamydomonas reinhardti) decreased development rates, body size, clutch size and survivorship; the sex ratio did not vary significantly from 1:1. Small container volumes had the same effects as low food concentrations, except that naupliar development time was not affected and survivorship showed greater variability. Because the copepod parameters exhibited maximum responses when food was abundant, even in the smallest container volume, it was concluded that container volume did not directly influence these parameters but exerted its effect through food availability.Larger life history stages were affected more than smaller life history stages by low food levels. In part, this was attributed to a laboratory artifact in which depletion of food by larger animals was greater than by smaller animals and, in part, to a real effect of low food concentration. A possible explanation of this real effect came from comparisons of these results to data from D. dorsalis fed phytoplankton from a Florida lake. The comparisons suggested that nauplii may be more efficient feeders on, or utilizers of, small food items such as Chlamydomonas.Numerous studies of natural zooplankton populations have correlated concentration of food with responses of various life history parameters. Although such studies have been useful in suggesting factors which may influence these parameters in nature, it has often been impossible to separate the effects of food from other factors, e.g., temperature, water quality and predation.For this reason, laboratory studies have been undertaken to elucidate the relationships between food concentration and zooplankton life history parameters. There have been many studies of the effects of food concentration on rotifers (e.g.

Food Resources, Survivorship, and Reproduction of the Omnivorous Calanoid Copepod Epischura Lacustris

“…Similar relationships between algal concentration and egg production have been reported for several herbivorous copepods from both marine (Checkley 1980, Uye 1981, Durbin eta!. 1983, Runge 1984, Smith and Lane 1985 and freshwater environments (Woodward and White 1981, Elmore 1982, Williamson eta!. 1985.…”

A perspective on the use of cohort analysis to obtain demographic data for copepods1

“…Thus T,, 1 is typically close to T,, albeit usually somewhat longer (Geiling and Campbell 1972). Similar data exist for freshwater copepods, for which Ti+ ,/T, typically falls in the range 2/3-3/ (Elmore 1982).…”

Food limitation in naupliar and adult Diaptomus pallidus1

“…In Calanus pacificus, stage VI nauplii are more vulnerable to starvation than are stage III nauplii, but both stages die within a week without food (Fernandez 1979). Elmore (1982) reported that nauplii of Diaptomus dorsalis are less sensitive than copepodites to low food concentrations. This suggests that developing copepodites are more vulnerable to low concentrations of food than both nauplii and adults or that there are real interspecific differences in vulnerability of the two species to low food or, as Elmore suggests, his results may be an artifact of his experimental design.…”