Allozyme analysis of two polymorphic enzymes in a natural population of Lecithochirium musculus

Genetic variability among 112 individuals of Lecithochirium musculus from Anguilla anguilla from northwestern Spain was examined using allozyme analysis. Starch-gel electrophoresis was used to investigate the genetic variation in two polymorphic enzymes, glucose phosphate isomerase (GPI) and phosphoglucomutase (PGM). The banding patterns obtained for GPI were consistent with a dimeric structure for this enzyme and with single-locus control. The inferred genotype frequencies did not significantly differ as compared with those predicted by the Hardy-Weinberg equation. Two PGM loci were detected (Pgm-1 and Pgm-2). Pgm-1 was polymorphic and showed a striking departure from Hardy-Weinberg predictions (total absence of heterozygotes for alleles in high frequencies), raising the possibility of the existence of two reproductively isolated populations. However, other reasons for this observation are discussed.