Amino acid and protein changes in the haemolymph of developing fourth instar Chironomus tentans

Abstract

The concentration of free amino acids, total soluble protein, and haemoglobin in the haemolymph of fourth instar Chironomus tentans was investigated. The concentration of the free amino acid pool increases between the early (15.7 mM/l) and mid-(33.9 mM/l) fourth larval stages followed by a decline during the late (16.9 mM/l) fourth larval period. Alanine, serine, and the amides of aspartic acid and glutamic acid are the predominant free amino acids at all stages. Physiological fluid analysis of late fourth instar haemolymph detected 32 ninhydrin positive components including 18 common amino acids plus homoarginine, ornithine, citrulline, β-alanine, α-aminoadipic acid, α-aminoisobutyric acid, and sarcosine. The concentration of total soluble protein steadily increases during fourth instar larval development to a maximum of 9.3 g 100 ml followed by a decline during the pharate pupal period. A similar pattern of variation occurs in haemoglobin content which comprises from 51 to 66% of Chironomus tentans haemolymph protein. The mM percentage of individual amino acids of total haemolymph protein varies little during the fourth instar. At all stages alanine and aspartic acid are the predominant amino acids.