Horizontal starch gel electrophoresis was used to analyze muscle tissue for the variation in 11 enzymes at 17 allozymic loci in three proposed species of the genus Scylla: S. serrata, S. tranquebarica, and S. oceanica. Seven loci were polymorphic at the 17 loci, and at three loci, EST*, LAP-2*, and SOD* gene replacement occurred. The average genetic distances between S. serrata and S. tranquebarica, S. tranquebarica and S. oceanica, and S. serrata and S. oceanica were 0.059, 0.126, and 0.187 respectively, with the relationship between S. serrata and S. tranquebarica being relatively similar. The genetic distances between local populations were very small (0-0.003) within the respective species. The gene replacement at the three loci and the genetic distances between species suggest that the genus Scylla includes at least three species.
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