Preliminary study on performance of triploid Thai silver barb, Puntius gonionotus.
The triploid chromosome condition was induced in Thai silver barb (P. gonionotus) by application of cold shock (2°C) to eggs at time intervals after activation of 0.5 min with a duration of 10 min which resulted in mean triploidy yield of 72.5% at 9 months of age. Growth rate of the 2- to 9-month-old, cold shock group (0.1-6.2 g/month) did not differ from that of the control (0.1-5.7 g/month). Gonadal somatic indices (GSI) of presumed triploid males and females were lower than that of control (GSI values of the presumed triploids were 35.0-60.2 and 28.7-75.9% of control males and females, respectively). Spermatogenesis and oogenesis were retarded in triploids. However, all stages of spermatogenic cells were observed in triploid males, including few spermatozoa. Oocytes of triploid females did not undergo vitellogenesis while normal oogenesis was observed in diploids. Nuclear volume of red blood cells of triploid fish was 1.63-times larger than that of diploids.