On the Nutrition and Metabolism of Zooplankton II. The relationship between the marine copepodCalanus helgolandicusand particulate material in Plymouth sea water, in terms of amino acid composition

Abstract

The amino acid composition of adult female Calanus helgolandicus Claus and particulate material at station L4 has been analysed from March to December. The average concentration of amino acid nitrogen in Calanus was 7·7% of the dry body weight and accounted for 83% of the total nitrogen. The average level of amino acid nitrogen in the particulate material was 11·9 μg/1. and accounted for 54% of the total nitrogen.The relative quantities of amino acids in Calanus remained remarkably constant throughout the year. The relative quantities of amino acids in particulate material were more variable.The rate of respiration of Calanus measured at 8°C varied from 31 μl. O2/mg. dry body weight/day in winter (December–February) to 79 μl. O2/mg dry body weight/day in summer (April–August).Starving winter Calanus lost 1·8% and starving summer Calanus 2·1% of their dry body weight as amino acids each day. In order to replenish its daily losses of amino acids winter Calanus must sustain a filtering rate of about 30 ml./animal/day: the corresponding value in summer is greater than 50 ml./animal/day.The amino acid composition of Skeletonema costatum is so close to that of the particulate material in the sea, that, as far as amino acids are concerned, Calanus would gain no nutritional advantage by selecting the diatom in preference to the amino acid containing fraction of particulate material as a whole.