Sexual dimorphism in sphaeromatid isopods (Sphaeromatidae) recorded from Pakistan coast, Northern Arabian Sea

Sexual dimorphism is one of the important and striking diagnostic features in sphaeromatid isopods. In all genera primary dimorphism is evident between ovigerous and non-ovigerous females and males based on the presence or absence of secondary sex characters i.e. appendix masculine and penes in males, oostegites in females. Uptill now sixteen Species in 11 genera belonging to the family Spaheromatidae have been recorded and described from the Pakistani waters. Among eleven genera, four genera Clianella Boone. 1923; Cymodoce Leach. 1814: Paracilicae Stebbing, 1910 and Poracerceis Hansen. 1905 show pronounced sexual dimorphism. In the present work these differences in the male and female individuals of the same species and genera have been discussed and shown by drawings, oil the basis of which in the past they were supposed to belonging to different species.