[Histological study of rainbow trout [Oncorhynchus mykiss] after administration of 17 alpha- methyl testosterone]

ABSTRACT

Study of histological changes in gonads of fish received a variety treatment of 17-alpha methyl testosterone. Rainbow trout [Oncorhynchus mykiss]. Descriptive study. Application of 17 - alpha methyl testosterone [MT] using immersion and/or oral administration methods in two seasons and in 5 and 11 treatments along with a control group with no hormonal treatment for each season, respectively. In immersion method eyed eggs and larvae were immersed in 250 mg/l MT bath for 2 hours twice 4 and 8 days apart. In oral administration method newly feeding larvae were fed with food containing 0.5, 1, 2, 3 and 30 ppm MT for 60, 70, 90 and 120 days after commencing active feeding. Histological examination was carried out on gonads of 20 fish from each treatment as well as control group at the age of 11 and 24 months for two seasonal groups of fish, respectively. Masculinization and sterilization were successfully carried out on rainbow trout by using a variety treatment of MT. A range of histological changes were observed in gonads of different treatment groups. This included histologically normal males, normal females, intersex, totally atrophic gonads and sterile fish. In some testes a number of follicles were seen among the mass of spermatozoa. In intersex gonads both male and female cell types were observed alongside each other. Sterile gonads could be categorized as sterile males, sterile females as well as completely sterile containing residual male cells, residual female cells and no cells at all, respectively. in a number of specimens spermatozoan cysts were typically observed. Application fo 17-alpha methyl testosterone to rainbow trout at early stages of development could dramatically change the histological profile of gonads ranging from functional testes, to intersex, to sterility