Two sympatric forms (I and II) of the estuarine grapsid crab Hemigrapsus penicillatus from the Nanakita River (Sendai, Japan) were detected by starch gel electrophoresis. Form I consists of individuals possessing the allele 6PgdB, while Form II has the allele 6PgdC. Heterozygote individuals (genotype of B/C ) were not observed at the 6Pgd locus. Form I is also characterized by the alleles Aat-2C and PgmA, while Form II has the alleles Aat-2B and PgmB. Morphological analysis revealed that the patch of soft hairs on the male chela in Form II individuals is much larger than that in Form I. The above results suggest that the two sympatric forms are reproductively isolated and represent sibling species.
The Japanese Association of Benthology