Short-term storage of oocytes from the neotropical teleost fish Prochilodus marggravii

The loss of oocyte viability after ovulation is one of the limiting factors in controlled reproduction of several fish species. Experiments were performed with 15 feral Prochilodus marggravii female fish induced to spawn with crude carp pituitary extract to evaluate the viability of oocytes retained within the ovarian cavity (in situ storage) and outside of the ovarian cavity (ex situ storage). Because fertility rates rapidly declined after ovulation, simultaneously with an increase in the number of deformed larvae, P. marggravii oocytes could only be successfully stored for 1 h ex situ at room temperature ( approximately 26 degrees C). There was a highly negative correlation (r = -0.82) between fertilization and deformed larvae during in situ storage at approximately 26 degrees C. Ex situ cooling (18 degrees C) caused a drastic reduction in fertilization rates as compared with storage at approximately 26 degrees C. Oocyte structure was preserved during 2 h storage and the cortical reaction was induced before spawning. Since the micropylar apparatus remained open, it was not the primary cause for the loss of oocyte fertility. The cytoskeleton of the oocyte appeared to be affected since ooplasmic segregation was altered after 2 h storage.