The biochemical profiles of shell-diseased American lobsters, Homarus americanus Milne Edwards

The proximate (% of dry weight), amino (% of total amino acids) and fatty a cid (% of total fatty acids) profiles of tissues (muscle, hepatopancreas, h emolymph and exoskeleton) of American lobster, Homarus americanus (Milne Ed wards) affected with shell-disease, were compared with those of healthy, un affected animals. Muscle tissues of affected lobsters had significantly low er levels of carbohydrate and the protein profile had significantly lower r atios of arginine, threonine, serine and total essential amino acids. Howev er, the ratio of glycine was about 50% higher than in muscle tissues of hea lthy lobsters. Muscle tissues of affected lobsters had slightly higher rati os of 20:4n - 6 and 22:6n - 3. Affected lobsters had significantly lower he patosomatic indices. Their hepatopancreas contained significantly higher le vels of protein, 35% less lipid and 266% higher levels of ash, than healthy lobsters. The protein profile had significantly lower ratios of phenylalan ine, threonine, and proline, but significantly elevated ratios of arginine. The ratio of 20:5n - 3, was about half that of healthy lobster hepatopancr eas. Hemolymph of affected lobsters contained about 40% less protein, about 35% higher levels of ash and significantly higher histidine ratios in its protein profile than corresponding ratios in healthy lobsters. Ratios of ph enylalanine and threonine were slightly but significantly lower and ratios of 18:2n - 6 and 20:4n - 6 were significantly elevated than in healthy lobs ters. The ulcerated exoskeleton of affected lobsters had significantly lowe r levels of total carotenoids and ash, and significantly higher moisture co ntent and proportions of protein and lipid than the non-ulcerated parts, or the exoskeleton of healthy lobsters. The amino and fatty acid profiles of the exoskeleton of healthy lobsters and the non-ulcerated exoskeletal parts of affected lobsters were not significantly different from each other. How ever, the non-ulcerated exoskeleton of affected lobsters had slightly but s ignificantly lower total carotenoid content than the exoskeleton of healthy lobsters. The ulcerated exoskeleton had higher ratios of 20:4n - 6 and 22: 6n - 3. There are differences in the biochemical profiles of tissues betwee n healthy and shell-diseased lobsters. The higher accumulation of ash in th e hepatopancreas and hemolymph of affected lobsters may indicate problems i n the transport/deposition of minerals to the exoskeleton, or withdrawal of these nutrients from the shell. (C) 2000 Elsevier Science B.V. All rights reserved.