Morphological and biochemical heterogeneity in populations of Microgadus tomcod (Walbaum, 1792)

Varacalli, Vincenzo (1973) Morphological and biochemical heterogeneity in populations of Microgadus tomcod (Walbaum, 1792). Masters thesis, Memorial University of Newfoundland.

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Abstract

The tomcod, Microgadus tomcod, as compared to the other species of the same family, Gadidae, is a little known species. It inhabits both marine and freshwater environments and seldom undertakes long migrations. -- The muscle myogen, lactic dehydrogenase (LDH) and liver esterase patterns obtained by starch gel electrophoresis and the morphometric variation in specimens of the tomcod (Microgadus tomcod) from five localities are compared. The pattern variations observed in the electrophoretic analysis and the variations observed in the morphological analysis are discussed in relation to geographic location and temperature. -- The morphological and meristic data revealed a strong northward latitudinal cline. The main muscle myogen, LDH and esterase patterns are similar for all the populations but with polymorphism occurring in each. The populations can be separated using the ratios of the main patterns obtained. -- Numerical clustering analysis revealed three populations using the morphometric data. Using the biochemical data it revealed the New York population as differing the most.

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