Genetic control and variability of phosphoglucose isomerase (PGI) in eels from the Atlantic ocean and the Mediterranean Sea

Abstract

There is evidence in the scientific literature of differences in the genetic control of the enzyme phosphoglucose isomerase (PGI) in the European eel Anguilla anguilla and the American eel A. rostrata. Two PGI loci have been described in the former species, while 3 PGI loci have been reported in the latter. There is also evidence of differences in the tissue distribution of PGI isoenzymes in European eels from the English Channel and the Mediterranean Sea which suggest genetic diversity between the two populations. Studies carried out on two fairly large samples of Mediterranean (coast of Tuscany) and Atlantic (coast of Wales) A. anguilla, and on a small sample of A. rostrata, have permitted a clearer and more complete interpretation of the complex PGI electrophoretic patterns present in the tissues of eels. No difference, however, was observed in PGI genetic control between A. anguilla and A. rostrata: two loci encode PGI in both species. The patterns of tissue activity of PGI isoenzymes in the two samples of A. anguilla were essentially the same. There were, also, no significant differences in the PGI allele frequency between the two samples of European eels. These results, which support the genetic homogeneity of eels from different parts of Europe, are discussed in relation to the classical and more recent theories on the origin of the Atlantic and Mediterranean eels.