A study of the metabolism of Daphnia

Abstract

The literature concerning the metabolism of Daphnia is surveyed and in part re-interpreted to act as a frame for new work.

The size factor in relation to reproductive phenomena is analysed in detail. An account is given of the pre-adult growth of Daphnia. based on 207 individuals belonging to 9 species reared in standard conditions. The greatest growth increment does not always occur at the end of the adolescent instar; it may occur at the and of the pre-adolescent instar or, more rarely ever, earlier. The effects of environmental factors on growth and reproduction are reviewed; it is shown that lack of oxygen inhibits the growth of D. magna. A mature female of D. magna can assimilate enough material during each instar to produce eggs with a dry weight at least equal to that of her body after the eggs have been laid. The dry weight of the parthenogenetic eggs of D. magna diminishes by 16--25 per cent during embryonic development.

Storage metabolism and energy sources, respiratory metabolism, heart beat rate, caroterold metabolism and osmotic regulation are treated briefly. Some new observations on carotenoid-proteins in Daphnia are presented. The relation between the fat body and the ovary of Chydorua sphaericus is described.

Two critical methods of correcting the haemoglobin index and a means of comparing the abilities of intra-specific groups to synthesise haemoglobin are given. Intrinsic factors influencing the ability to synthesise haemoglobin are analysed. Males gain and lose haemoglobin more quickly than females. Specific, racial and age effects are described. The present state of knowledge concerning haem metabolism in Daphnia is reviewed.

The thesis concludes with a general summary which indicates the extent and limitations of our knowledge of the metabilism of Daphnia.