Histological Study of gonads in Euryglossa orientalis from Persian Gulf

Among more than 600 fish species in Persian Gulf، Soles are considered as one of the most economically important species. These fish is different from other fishes in morphological، functional and structural organs and like many other flatfish are less well known. The present study was designed to investigate the histological structure of gonads of Sole (Euryglossa orientalis) in two breeding and rest seasons. 40 Sole fish were collected from Zangi estuary (located in Mussa creek in the north of Persian Gulf) in early July and early October (non- breeding and breeding seasons) 2013. After biometry، gonadal tissues were dissected and weighed to determine Gonadosomatic Index (GSI). Then fixed in Bouin ''s solution. Histological specimens were transported to the histological laboratory. Tissue sections were prepared according to conventional methods include dehydration، clearing and paraffin. And then were cut down to 5 micron sections and stained. These tissue sections were studied by light microscopy. The result showed that different stages of germ cells in both male and female gonads. Although in breeding season mature cells were noticed، GSI index of testis and ovary in Sole showed significant difference between the two seasons.