Sulcus and outline morphometrics of sagittal otolith variability in freshwater fragmented populations of dwarf gourami, Trichogaster lalia (Hamilton, 1822)

Abstract

Studies on the anatomy of sulcus and outline morphometrics of the three population groups of Trichogaster lalia were carried out to examine the effects of anthropogenic stressors (dams and barrages) on the function-related morphological variability of the fish. Altogether 150 samples of the fish were procured from three geographically isolated rivers namely Ganga, Gomti and Yamuna. The features based on images and morphological indices of sulcus, otolith and body shape of the fish were analysed and compared using uni and multivariate statistical procedures. Rostrum, anti-rostrum and margins of sagittal otolith and cauda of sulcus predominantly varied among three population groups of the fish. Variations in geometric morphometrics of sulcus, otolith-outline, combination of both and body shape indicated the existence of three distinct groups of the fish where individuals of river Gomti and Ganga were found to be closer to each other compared to that of river Yamuna. Mantel test showed an overall good correlation between the morphometric data-sets based on otolith and body shape in delineating three groups of the fish. Understanding of the environmental factors influencing the variations in function-related morphology of the different groups of T. lalia is essential to identify the boundaries of the different groups of the fish and to implement the appropriate strategies for their conservation.