Indices of nutritional state in the western rock lobster, Panulirus longipes1 (Milne Edwards). I. Blood and tissue constituents and water content

Blood protein concentration in the western rock lobster, Panulirus longipes (Milne Edwards), decreased with starvation, but this decrease was due to increase in blood space as solid tissues were metabolized. The total amount of blood protein remained constant during starvation and throughout the moulting cycle, and may be used as a reliable measure of blood volume. No qualitative changes could be detected in blood protein constituents either during starvation or during the moulting cycle.Concentrations of blood non-protein amino acids were also related to blood volume, but there was a small, significant decrease in total amount after 4 weeks starvation.Concentrations of blood non-precipitatable total carbohydrates and blood glucose did not change significantly with starvation, but there were large changes due to the stress of handling.The water content of whole legs, whole abdomen, and abdominal muscle increased significantly with starvation. Protein and non-protein amino-acid concentrations in leg muscle did not change, but protein concentration in abdominal muscle was significantly lowered. Of all solids, those of the digestive gland showed the greatest decrease during starvation.It is concluded that quantitative measurements of blood constituents are meaningless unless related to blood volume. Blood total protein in conjunction with whole leg water content could provide a practical, simple, and non-destructive means of assessing nutritional state in populations of larger rock lobsters if the moulting history were precisely known, but would not be of use for smaller juveniles because of their relatively high moulting frequency. Other constituents (blood amino-acid or abdominal muscle protein concentrations, digestive gland solids, whole abdomen weights) are either not feasible as a field method or involve destruction of the animal. No satisfactory single index of nutritional state, suitable for field use with wild populations, has been found.