Ultrastructure of the chorion and the micropyle of an endemic cyprinid fish, Cyprinion tenuiradius Heckel, 1849 (Teleostei: Cyprinidae) from southern Iran

 The scanning electron microscope was used to investigate the ultrastructures of the egg membrane surface (unfertilized egg) of an endemic cyprinid fish, Cyprinion tenuiradius Heckel, 1849. The eggs of this species were almost circular in shape, had a smooth surface and one type II micropyle consisting of the flat pit and a long canal in the animal polar region. The micropyle region was not flat, micropyle was circular or oval in shape and the micropyle canal was located in its center. Round or oval accessory pores were also observed in the pit around of the micropylar canal. The surface of zona radiata was smooth with a uniform distribution of almost round pores with lips.