Biochemical Studies on Marine Zooplankton XII. Further Investigations on Euphausia Superba Dana

Interest has developed recently in the biochemical composition of zooplankton, particularly in relation to seasonal changes. An earlier study (Raymont, Srinivasagam & Raymont, 1971b) on deep frozen Antarctic krill, Euphausia superba, collected over approximately 5 weeks in December/January 1968/69 suggested that protein was the main constituent and lipid much more variable. Despite the variability the mean lipid content during January was distinctly higher than in the previous month, thus supporting the findings of Kryuchkova & Makarov (1969) that lipid content of krill tends to increase as the summer advances. However, collections of material from the Antarctic have tended to be limited both in location and season while methods of preservation have varied. It seemed desirable to follow changes in the biochemical composition of krill collected from a somewhat wider area and over a longer period. Moreover, the more extensive material gave opportunity for a more detailed examination of specific fractions, such as the amino acids of Euphausia superba. Preliminary investigations (Srinivasagam, Raymont, Moodie & Raymont, 1971) on the amino acid composition of protein hydrolysates showed good agreement with the results of some other authors. However, the findings of Burkholder, Mandelli & Centeno (1967) and especially of Moiseev (1970) showed certain differences.