Dry weight and chemical composition (CHN) in relation to population density of cultivatedTisbe holothuriae (Copepoda, Harpacticoida)

Abstract

The harpacticoid copepodTisbe holothuriae was cultivated at different densities in a running-water system. Dry weight and chemical composition (CHN) of both females and egg-sacs have been determined. Dry weight decreased significantly with increasing density from 3,48 to 1.94μg in egg-sacs, and from 10.80 to 6.58μg in females. Increasing density in both egg-sacs and females results in decrease of carbon, nitrogen and hydrogen contents, expressed as a percentage of dry weight of egg-sacs and females, respectively. Carbon decreases from 52.56 to 50.57% (egg-sacs) and 45.80 to 39.95% (⧫), nitrogen from 12.63 to 11.94% and 10.72 to 9.73% and hydrogen from 9.08 to 7.78% and 7.47 to 6.17%. The dry weight and elemental compositions of the egg-sacs varied in accordance with that of the females, however, a higher percentage of elemental content was observed in egg-sacs. The energy equivalents were calculated from the carbon content. This indicates that more energy was transferred from the maternal body into egg-sacs. The ratio of carbon to nitrogen did not show any marked variations; no clear relation appeared between C:N and density, indicating a relatively constant chemical composition in both females and egg-sacs.