Resolving Species Delineation of Four Portunid Crab Species of the Gulf of Mannar using Truss Morphometry
Resolving Species Delineation of Four Portunid Crab Species of the Gulf of Mannar using Truss Morphometry
Preetysh Nanda Patnaik1, V.K. Venkataramani1, N. Jayakumar1, R. Durairaja1, Adyasha Sahu 1 and C. Sudhan2*
ABSTRACT
The present study used truss morphometry to investigate species delineation of four portunid crab species from the Gulf of Mannar coast. Four closely related commercially significant portunid crab species such as Portunus pelagicus, Portunus sanguinolentus, Charybdis natator and Portunus gladiator were selected based on body morphometry and morphology to delineate them by employing a truss network. With regard to conventional morphometry in portunid species, only few characters are seemed to be diagnostic and many characters are found to be overlapping. Hence, Truss morphometry was attempted. Eleven truss distance landmarks were fixed on the cephalothorax dorsal surface using tpsUtil and digitized using tpsDig computer software package. A set of multivariate methods (Principal component analysis and Discriminant function analysis) was performed to make detailed investigation on distinction and pattern of morphological variations among all the four studied species, which revealed that there is significant variation in morphometrics of the portunid species. The first two components of the principal component analysis explained 99.99% of the overall variation. The first principal component (PC1) explained 83.74% while second principal component (PC2) accounted for 16.24% of the total variation. Four distinct species were confirmed by the scatter-plot from PCA and DFA. Wilks’ lambda tests of discriminant function analysis revealed highly significant (P < 0.001) differences in morphometric characters across all the species. The findings of this study justify the use of truss networks for diagnostic identification for several species of portunid crabs apart from conventional morphometry. The study will be of immense use particularly in providing intriguing insights for species identification and characterization, besides, this will also clearly reveal any ambiguity in taxonomical clarification.
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