Liver and muscle composition of mature lampreys.

Abstract

Lengths, weights, liver weights, and color of sea lamprey (Petromyzon marinus) from Cayuga Lake and Lake Superior and of American brook lamprey (Lampetra lamottei) were recorded. Liver and muscle of the sea lamprey samples were analyzed for fat, water, and protein content. American brook lamprey were analyzed only for fat and water content. In both populations of sea lamprey, male livers had a higher fat content and lower water content than female livers, but the protein content was similar in the sexes. The liver composition of the Lake Superior sample, which represented a sample of late migrants, was not significantly different from the liver composition of earlier spawners (Lake Cayuga sample). In both populations of sea lamprey there was no sexual difference in muscle composition; however, the muscle fat was reduced and the muscle water was elevated in the late migrants as compared to the earlier migrants. No sexual differences in the composition of either the liver or the muscle were found in American brook lamprey. Although the brook lamprey examined were early migrants both liver and muscle had a reduced fat content when compared to early sea lamprey migrants.Using Lake Cayuga data, the approximate composition of male sea lamprey liver at the start of the spawning migration was 20% fat, 50% water, and 15% protein. Comparable values for females were 5% fat, 75% water, and 15% protein. The muscle composition, of both sexes at the beginning of the migration, was 8% fat, 70% water, and 20% protein.