Post-ovulatory egg viability in the snapper Pagrus auratus (Sparidae)

Abstract

The role of gonadal steroids in maintaining post-ovulatory egg viability was investigated in the snapper (Pagrus auratus), a daily-repeat-spawning teleost. Ovulated eggs were held in vitro in L15 medium, or in L15 medium supplemented with gonadal steroids or gonadotrophin, to investigate any direct effects of reproductive hormones on post-ovulatory egg viability. The viability of eggs retained in the oviduct decreased with increasing time after ovulation, to give fertilization of below 50% after 6 h. The viability of eggs held in L15 medium was at least as good at that of eggs held in vivo. Storage of eggs in L15 medium supplemented with the reproductive hormones testosterone, 17α-hydroxyprogesterone, 17α,20β-dihydroxy-4-pregnen-3-one and human chorionic gonadotrophin did not improve or reduce viability relative to controls, suggesting that the hormones investigated have no direct effect on post-ovulatory egg viability.