(26) Histological Changes of Testis Stages in Oreochromis Andersonii

     The aim of this study was to gain knowledge of reproductive stages of the testis in order to understand male reproduction in Oreochromis andersonii (three-spot tilapia). As far as we are aware, there are few resources... [ view full abstract ]

     The aim of this study was to gain knowledge of reproductive stages of the testis in order to understand male reproduction in Oreochromis andersonii (three-spot tilapia). As far as we are aware, there are few resources dealing with gonadal staging of three-spot tilapia. Testis histology was completed for 27 sexually mature males collected from five sites in the Okavango River Delta from March to April 2016. Of the fish examined, 15 specimens were stage 1, six specimens were stage 2, four specimens were stage 3, and one specimen was stage 4. In fish reproduction, stages refer to degree of testis “ripeness,” with stage 4 being the most progressed stage. Microscopy reveals spermatogonia, spermatocytes, spermatids, and spermatozoa collected inside cysts in the lobules of the testis.  Mature spermatozoa also aggregate in the sperm ducts for later release during fertilization.  In the riper stage 3 and 4 specimens, lobules are filled with more mature spermatozoa, while the less ripe stage 1 and 2 specimens contained more of the earlier sperm stages.  Some stage 1 specimens also display empty lobules as well as lobules that have degraded spermatozoa from previous mating cycles. Knowledge of male gonadal stages has implications for tilapia aquaculture and conservation.  It is important to understand how the fish matures and reproduces in order to effectively manage commercial and wild populations.