Histological and histometrical study of common carp ovarian development during breeding season in Khouzestan province in Iran

This survey was aimed at detecting histological and histometrical changes of Common Carp ovaries in Khouzestan Province climate conditions. The goal was to determine the ovarian status in the breeding period of the reproductive cycle. Ovaries of 49 Common Carp brooders were collected from April to October, 2010. The samples were taken from the anterior, median and posterior portions. 5-6µ sections were made by the paraffin embedding method and stained by H&E and PAS. The results showed that the breeding season in Common Carp in this area takes at least 7 months and spawning continues from April to October. It seems that the previtellogenesis and vitellogenesis stages are short in the Khouzestan climate conditions and this species rapidly enters into the maturation phase. It seems that Common Carp have the ability to spawn three times during an annual cycle in the Khouzestan climate conditions. Histological and histometrical results showed that in the three stages, from anterior to posterior, the mean percentage of vitellogenic follicles increased significantly (p<0.001). The minimum diameters of follicles were observed in the chromatin nucleolus and the maximum diameters were observed in the secondary vitellogenic follicles. Zona pellucida appeared in the cortical alveolus follicles and reached to a maximum thickness in the secondary vitellogenic follicles. The diameter of the nucleus increased gradually and it reached to a maximum diameter in the primary vitellogenic follicles. There was a significant difference in parenchyma percentages between the three stages of the reproductive cycle from the previtellogenesis stage to the vitellogenesis stage, and then the maturation stage. This ratio increased significantly (p<0.05).