Overripening of ovulated eggs in goldfish, Carassius auratus: II. Possible involvement of postovulatory follicles and steroids

Abstract

Changes in steroid hormone levels in the serum and ovarian fluid during overripening were studied in goldfish. Ovulated eggs retained in the ovarian cavity became overripe at around 12h after ovulation based on loss of fertilizability, with advanced degeneration by 24h. Blood and ovarian fluid were taken at 0, 3, 6, 12, 18 and 24h after ovulation. Both serum and ovarian fluid progesterone (P) showed a highly significant decline by 18h with a further decline by 24h; P levels were higher in the ovarian fluid. Serum 17α,20β-dihydroxy-4-pregnen-3-one(17,20β-P) levels showed a progressive and more rapid decline, decreasing significantly by 12h with further decreases by 18h and 24h. Serum testosterone (T) levels increased significantly at 3h and remained high till 18h, thereafter they declined to the 0h level. No significant changes in estradiol-17β (E2) levels were observed in the serum, except for a significant difference between 6 and 24h. There were no significant changes in ovarian fluid E2, T or 17,20β-P levels.The postovulatory follicles (POFs) showed degenerative changes which corresponded to the decline in P and 17,20β-P. The hypothesis that overripening may be associated with declining levels of P or 17,20β-P was tested in vivo by immersing just ovulated females (0h) in P or 17,20β-P solutions for 12h, and in vitro by immersing just-ovulated eggs (0h) in ovarian fluid with an anti-serum against P (Anti-P). In the former, P at 0.05 ppm significantly enhanced the fertilization rate of ovulated eggs stripped from the females at 12h while 17,20β-P did not produce a significant effect at the tested concentrations (0.025 and 0.05 ppm) on the fertilization rate. In the latter, anti-P significantly lowered the fertilization rate of 0h ovulated eggs after 6h incubation. The evidence suggests a role of P in the maintenance of viability of ovulated eggs.

Fish Oocyte Ageing and its Effect on Egg Quality

“…No significant changes in the estradiol-17(E2) levels were observed in both the ovarian fluid and serum as well as in ovarian fluid E2, T or 17 ß,20-P levels. The role of progesterone in the maintenance of egg viability after ovulation was suggested (Formacion et al, 1995). Liley et al (1986) reported that increased hormone levels might contribute to an acceleration or synchronization of breeding or be responsible for vigorous sexual activity.…”

“…In goldfish, Carassius auratus, both the serum and ovarian fluid progesterone levels were highest at the time point of ovulation and decreased significantly 18 hr post ovulation, when the eggs completely lost their fertilizing ability (Formacion et al, 1995). The progesterone levels in the ovarian fluid decreased during oocyte overmaturation (Formacion et al, 1995). The serum 17a,20ß-dihydroxy-4-pregnen-3-one levels showed a progressive and more rapid decline during ageing of oocytes in goldfish, while the hormone generally increased in the ovarian fluid.…”

Ovarian fluid in the three‐spined stickleback Gasterosteus aculeatus: effects of egg overripening and sex steroid treatment

“…P4 treatment resulted in copious amounts of ovarian fluid in both spawned and overripe fish, whereas the effect of E2 was less clear. Formacion et al (1995) showed that immersion of newly ovulated female C. auratus (ovulation induced by hCG) in a solution containing P4 increased the fertilisation rates of stripped eggs at 12 h while 17,20β-P did not. Also, immersions in vitro of just ovulated eggs in ovarian fluid containing anti-serum against P4 decreased the fertilisation rates after 6 h incubation suggesting a role of P4 (or other progestogens cross reacting with the antiserum) in delaying overripening (Formacion et al, 1995).…”

“…The time that this takes depends on species and temperature (Bromage et al, 1992(Bromage et al, , 1994Gillet, 1991;Springate et al, 1984). In most fishes, ovulated eggs undergo a rapid decrease in quality over a few hours (turbot Scophthalmus maximus (L. 1758) McEvov, 1984; goldfish Carassius auratus (L. 1758) Formacion et al, 1993Formacion et al, , 1995Atlantic halibut Hippoglossus hippoglossus (L. 1758) Bromage et al, 1994). On the other hand, salmonids can hold their ovulated eggs for several days without loss of egg viability (Aegerter & Jalabert, 2004;Springate et al, 1984).…”

Effects of delayed fertilization on embryo viability in walleye Sander vitreus (Mitchill): the role of maternal effects

“…: þ1 705 671 3828; fax: þ1 705 671 3857; email: tjohnston@laurentian.ca a series of changes following ovulation that generally render them less viable over time, a process termed overripening (Sakai et al, 1975;Mollah & Tan, 1983;Hay, 1986;Fitzpatrick et al, 1987). Changes in the morphological and histological appearance of ova and postovulatory follicles (Formacion et al, 1995;Lahnsteiner, 2000), biochemical composition of ova and ovarian fluid (Craik & Harvey, 1984;Lahnsteiner, 2000; and in the abundance of specific mRNA transcripts (Aegerter et al, , 2005 all occur in the postovulation period. Decreases in viability can take the form of reduced rates of fertilization and hatching success (Bromage et al, 1994) and increases in developmental abnormalities and numbers of aneuploid, polyploid or mosaic offspring (V´arkonyi et al, 1998;.…”