Genetic variation of phosphoglucose isomerase isoenzymes in fish of the orders Ostariophysi and Isospondyli

Isozymes of glucosephosphate isomerase (PGI) in fishes of the subclass actinopterygii

A compilation of the species of fishes of the subclass Actinopterygii for the study of the PGI isozyme system is given. PGI appears to be codified by more than one locus in fishes; 65% of the species analysed here have two loci for PGI. PGI duplication in fishes and the relationship of isozymes of PGI with temperature and metabolism are discussed.

Gene action in fish of tetraploid origin. II. Cellular and biochemical parameters in clupeoid and salmonoid fish

By use of cell size, protein and hemoglobin content, and enzyme activities as markers, it becomes apparent that in the course of evolution the gene expression of anciently tetraploid fish of the order Ostariophysi was diploidized, but no such regulatory mechanism has evolved in the phylogenetically tetraploid species of the order Isospondyli. This finding is discussed in terms of possible selective neutrality of tetraploid expression and the phylogenetic age of Isospondyli.

Gene action in fish of tetraploid origin. I. Cellular and biochemical parameters in cyprinid fish

In phylogenetically diploid and tetraploid Cyprinid fish species, erythrocyte volumes, protein contents, and mean activities of the enzymes LDH, 6PGD, and PGI per cell per active gene locus decline with increasing DNA contents. These findings are assumed to reflect an evolutionary tendency of polyploids to regulate their genic activity down to the level of the diploids.