The triploid chromosome condition was induced in Thai silver barb Ž . Puntius gonionotus by
application of cold shock 2Ž . 8C 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
2–9-month-old, cold shock group 0.1–6.2 g Ž . rmonth did not differ from that of the control
Ž . Ž. 0.1–5.7 grmonth . 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% Ž
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 RBCs of triploid fish was Ž .
1.63 times larger than that of diploids