Classification of Three Crab Morphs in the Genus Scylla using Morphometric Analysis

Abstract

One hundred and fifty-four male mud crabs in the genus Scylla were collected from different coastal areas of the Gulf of Thailand and the Andaman Sea, including Trat, Ranong and Surat Thani Provinces. They were classified into three morphs, “black”, “white” and “violet” based on their phenotypes and body colors. Fifty-one morphometric characters were observed and used for canonical variate analysis (CVA) and Mahalanobis’ Distance analysis. CVA results showed completely separation of three morph clusters with true correlation to its phenotypes and without overlapping among different clusters. Morphological differences among crab morphs were confirmed by considerably high value of Mahalanobis’ Distance in the range of 53.283 – 60.806 but those within morphs were in the range of 6.922 – 15.027. Both CVA and Mahalanobis’ Distance as well as their morphological data suggested that these three crab morphs of “black” “white” and “violet” should be classified into three distinct species of S. olivacea, S. paramamosain and S. tranquebarica, respectively.