Effects of cold-shock triploidy induction treatment on cell cleavage, hatching rate, and survival of triploid larvae of spotted sand bass (Paralabrax maculatofasciatus)

Three experiments assessed the effects of cold-shock induced triploidy on (1) the incidence of abnormal cell cleavage during embryogenesis, (2) hatching success and the proportion of live yolk-sac larvae in normally cleaved versus abnormally cleaved embryos, and (3) survival of triploid larvae of spotted sand bass (Paralabrax maculatofasciatus). All spawns were obtained by hormonal induction (LHRHa). Triploidy was induced by cold shock shortly after fertilization. In experiment 1, the percentage of abnormal cell cleavage was significantly higher (P < 0.05) in the cold-shocked group than in the control group, while the hatching rate and the proportion of live yolk-sac larvae were significantly lower (P < 0.05). In experiment 2, when normally and abnormally cleaved embryos from the control and cold-shocked groups were incubated separately, normal cleaved embryos in the cold-shocked group showed a significantly higher hatching rate and proportion of live yolk-sac larvae than abnormally cleaved embryos in the same group. No difference was observed in the control group. In experiment 3, a significant decrease (P < 0.05) in the triploidy count was observed throughout the larval period. Final survival was drastically lower for triploid larvae compared to cold-shocked diploids and untreated eggs. Low triploidy percentages at the end of the larval period would seriously hinder the development of triploid sand bass culture. Se realizaron 3 experimentos para evaluar los efectos de la triploidia inducida por choque frio sobre (1) la incidencia de division celular anormal durante la embriogenesis, (2) la tasa de eclosion y la proporcion de larvas vitelinas vivas en los embriones con division celular normal contra los embriones con division anormal y (3) la supervivencia de larvas triploides de la cabrilla arenera (Paralabrax maculatofasciatus). Los desoves se obtuvieron por induccion hormonal (LHRHa). La triploidia se indujo por choque frio poco despues de la fecundacion. En el experimento 1, el porcentaje de embriones con division anormal fue significativamente mas alto (P < 0.05) en las larvas tratadas con choque frio que en el grupo control, mientras que la tasa de eclosion y la proporcion de larvas vitelinas vivas fueron significativamente mas bajas (P < 0.05). En el experimento 2, cuando los embriones con divisiones normales y anormales de ambos grupos fueron incubados por separado, los embriones con divisiones celulares normales en el grupo de choque frio presentaron una tasa de eclosion y una proporcion de larvas vitelinas vivas significativamente mas altas que los embriones con division celular anormal del mismo grupo. No se observaron diferencias en el grupo control. En el experimento 3, se observo una disminucion significativa (P < 0.05) en la cantidad de triploides a lo largo del periodo larvario. La supervivencia final fue drasticamente menor para las larvas triploides en comparacion con las larvas que resultaron diploides despues del choque frio o que no recibieron tratamiento. Los bajos porcentajes de triploides al final del periodo larvario limitan el desarrollo del cultivo de la cabrilla arenera triploide.