Sexual Dimorphism in Mystus Gulio (Hamilton-Buchanan)

Understanding of sexual dimorphism in fish is an uphill task and the phenomenon is paradoxical in different species. Considering the importance, a study was carried out to identify the distinguishing morphological characters between the sexes of M. gulio. It is an edible fish with therapeutic qualities and is recommended by physicians as diet during convalescence. Statistical analysis of various morphological measurements of 383 numbers of freshly collected specimens was the tool of the study. Together, some morphological peculiarities have also been noted for the seasonal sexual dimorphism including, Males are usually smaller than females with a clear white spot in the tip of fork. In addition to this, in the case of males there is a protuberance with a free tapering end lying further back to the body on ventral side. Regarding females, there is an additional aperture behind the anal opening. The generative openings terminate to this aperture behind the anal opening and this probably represents the 'vagina'. In case of the female, the generative aperture is far behind the anal opening and is simple. During breeding season, in male, additionally there exists a spear shaped thickening on the base of the caudal fin ie, caudal thickening. These are absent in the case of females.