Measurement of tissue lipid reserves in the American lobster (Homarus americanus): hemolymph metabolites as potential biomarkers of nutritional status

Abstract

Evaluation of hepatopancreas (HP), pincher claw muscle (PCM), crusher claw muscle (CCM), and abdominal muscle (AM) lipid content in 86 recently caught, adult, male and female American lobsters, Homarus americanus, in the Northumberland Strait, PE, Canada, using the Folch method identified lipid as a significant metabolic reserve. The HP was the primary lipid reservoir in male and non-berried females. Among five moult categories (late inter-moult (mc-1), early pre-moult (mc-2), mid pre-moult (mc-3), late pre-moult (mc-4) and post-moult (mc-5)), devised for the study, the prominent trend observed was a post-moult depletion of lipid reserves in the HP, PCM, and AM. An increased lipid index (LIn) in both CCM and PCM at late pre-moult suggested a differential distribution to provide needed energy in the immediate post-moult foraging period. Hemolymph plasma concentrations of triglyceride (TG), cholesterol (CHOL), and total protein (TP) were highly correlated (TG > CHOL > TP) with HP lipid content in male lobsters only, with the highest values obtained for inter-moult animals. Use of all three parameters in multiple linear regression model improved fit from 0.6656 using TP alone to 0.8226. Hemolymph evaluation presents a non-lethal alternative to assess hepatopancreas lipid content in American lobsters when sex and moult stage are taken into account. These data emphasize the importance of timing and subject selection when using blood chemistry to aid in the monitoring of lobster populations, e.g., for predicting growth on an individual or population basis, response to changing environmental conditions and reproductive capacity.