Moult cycle of the decapod Nephrops norvegicus (Linnaeus, 1758): Description of stages and sequential changes in haemolymph protein and haemocyanin

Crustacean life is dominated by the moult cycle, a series of regular physiological and behavioural changes that enable the organism to grow. A method is described to determine the individual stages in the cycle of the species Nephrops norvegicus. Based on a combination of carapace hardness and pleopod morphology, 14 stages and substages are identified. The technique is used to investigate changes in haemolymph total protein and haemocyanin across the cycle. Peaks are detected in both parameters at the final stage of intermoult and during active pre-moult suggesting an increase in metabolic activity. In addition to validating the moult staging method, the results highlight the importance of considering the underlying physiology of lobsters in either experimental or ecological studies.