Geometric Morphometric Analysis of Arius manillensis and Arius dispar (Siluriformes: Ariidae) Populations in Laguna de Bay, Philippines
Brian S. Santos and Jonas P. Quilang*
Genetics Research Laboratory, Institute of Biology, College of Science,
University of the Philippines, 1101 Diliman, Quezon City, Philippines
Geometric morphometrics has become a widely used tool in studying shape variation in fish populations. In this study, geometric morphometrics was used to examine shape variation in the sea catfishes Arius manillensis and A. dispar. The endemic species A. manillensis and the native species A. dispar constitute major fishery resources in Laguna de Bay. Thus, they are economically important species. The two species look very similar externally, but they can be distinguished by examining the tooth patch morphology on the palate. However, within each species, there are variants of tooth patch morphology. Shape differences between A. manillensis and A. dispar, between populations, and between variants within each species, were determined. Samples were obtained from Binangonan, Tanay, and Calamba areas of Laguna de Bay. Shape differences between species, between morphs within species, and among specimens of different sites were significant, but the groups were difficult to differentiate due to high overlaps in Canonical Variate Analysis (CVA) plots and low Mahalanobis distance-based correct classification percentages. This was attributed to possible introgression between A. manillensis and A. dispar product quality.
The sea catfishes Arius manillensis Valenciennes, 1840 and Arius dispar Herre, 1926 are commercially important to local fishery in the Philippines. A. manillensis is endemic to the Philippines and although A. dispar is native to this country, it is also found in other parts of the world. These two species are locally known as kanduli. In the 1920s kanduli used to be the most abundant fishes in Laguna de Bay, a 90,000-ha lake which is the largest in the Philippines (Mane 1929; Aldaba 1931; Mercene 1978). . . . . . . . . . . . .
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