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Lactate Dehydrogenase Isozymes of Gadiform Fishes: Divergent Patterns of Gene Expression Indicate a Heterogeneous Taxon

1981; American Society of Ichthyologists and Herpetologists; Volume: 1981; Issue: 3 Linguagem: Inglês

10.2307/1444560

1938-5110

James B. Shaklee, Gregory S. Whitt,

Fish biology, ecology, and behavior

The lactate dehydrogenase (LDH) isozyme patterns of 35 species of gadiform fishes were analyzed by starch gel electrophoresis and immunochemical procedures. All species exhibited the three expected homopolymers of LDH-A4, B4 and C4. Although the specific properties (absolute net charge and tissue abundance of each isozyme) of the LDHs of each species were unique to that species, certain general features of the LDH patterns characterized most or all species in a given higher taxon (genus, family, suborder). Thus, gadids generally exhibited a highly anodal LDH-A4 homopolymer while ophidiids had one which was nearly isoelectric; macrourids had high levels of LDH-B4 in nearly all tissues while zoarcids only expressed the B4 homopolymer in eye and brain, and so forth. In contrast to the homogeneity of LDH-C4 expression characteristic of nearly all higher teleost groups, a major dichotomy of LDH-C4 patterns was observed within the Gadiformes. The 19 species examined in the suborders Gadoidei and Macrouroidei all possessed a cathodally migrating, liver-predominant C4 isozyme while all sixteen species examined in the suborders Ophidioidei and Zoarcoidei exhibited a highly anodal, eye-specific LDH-C4. Because each of these forms of LDH-C gene expression represents a derived or specialized state relative to the situation in lower bony fishes, and because of the debatable nature of the morphological evidence originally used to justify the inclusion of these four groups in the same order, we suggest that the order as presently defined represents an unnatural grouping. We recommend revision and suggest that the ophidioids and zoarcoids should be removed from the Gadiformes.