Histological Study of Ovarian Development and Sexual Maturity of Kutum (Rutilus frisii kutum Kamenskii, 1901)

Abstract

Studies were conducted on the changes occurring in the ovaries of adult female Kutum, (Rutilus frisii kutum Kamenskii, 1901) in Bandar-e Kiashahr in Southwestern of Caspian Sea during a yearly cycle (between two spawning period) from October 2007 to April 2008. No abnormalities or pathological changes in the ovarian or body of the investigated fish were detected. The aims of this study were confirm to timing, frequency and duration of the spawning period, monitor changes in the gonado-somatic index (GSI), relate (GSI) to the histological characteristics of the ovaries and describe the stages of Kutum oocyte and ovarian development. Gonadal samples were taken monthly from the females stained with HandE stain and Samples were studied by light microscope. Different stages of oocyte development (nucleus changes, oocyte diameter and forming of yolk vesicle, yolk granules and lipid droplets) were surveyed. Six maturity stages were observed during our study that included: Virgin stage (I), Maturing virgin (II), Developing (III), Gravid (IV), Spawning (V) and Spent (VI). This study has shown that gonadosomatic index (GSI) began to increase in March and reached the highest value (29.47±4.2) in April and then decreased sharply in early may. According to the results gonad development of Kutum was synchronous group.