Moult stage-dependent variability of haemolymph ammonia and total protein levels of Crangon crangon (L.) (Crustacea, Decapoda)

Abstract

Abstract Haemolymph ammonia and total protein levels showed similar patterns of quantitative change, and a positive, linear relationship, during the moult cycle of Crangon crangon (L.) (Crustacea, Decapoda), Concentrations were generally lowest after ecdysis (120.5 μmol ammonia l-1; 3.7 g total protein 100 ml-1) and increased through intermoult and early premoult. Premoult (stages D0 ED3) ammonia concentrations were relatively constant (192.1–212.2 μmol ammonia l-1), whereas total protein values were more variable (5.7–7.8 g 100 ml-1). Ecdysis was accompanied by significant (P<0.05), near-identical decreases (34.9% & 35.1% respectively) in haemolymph ammonia and total protein concentrations. Two different mechanisms appear responsible for these changes: a passive drop in protein levels (attributed to haemolymph dilution), and a regulated decrease of ammonia levels. These data show moult stage-dependent ammonia efflux rates to be independent of haemolymph ammonia concentrations.