IMPROVING HYBRID CATFISH PRODUCTION: IMPACTS OF PARENTAL EFFECTS AND GAMETE INTERACTIONS
Catfish farming accounts for nearly 70% of total U.S. freshwater aquaculture production, where the channel catfish, Ictalurus punctatus ♀ × blue catfish, I. furcatus ♂ hybrid constitutes >50% of the harvest. Although the catfish industry has seen sustained growth there are still challenges associated with fertility , broodstock selection, and inconsistent production of hybrid catfish fry. In order to address these challenges, several experiments were conducted with the following objectives: 1) determine optimal sperm density required to fertilize eggs using assisted reproductive techniques, 2) assess sperm performance by incorporating female ovarian fluid into the sperm activation environment, 3) identify mechanisms of sexual selection and gamete interactions, and 4 ) examine gene expression profiles between low vs. high quality eggs at different stages of embryonic development.
Preliminary results demonstrate that previous sperm densities required for fertilization were overestimated (1.25 × 105:1 to 1.2 × 107:1 sperm per egg) and that a ratio of 1 × 104:1 sperm per egg maximizes hatch success of hybrid fry (Fig. 1A). Secondly, our results confirmed ovarian fluid can play a critical role in the fertilization environment by increasing sperm motility, velocity (Fig. 1B), and longevity. Significant sperm-ovarian fluid effects were also evident that caused differential sperm performance and sexual selection at the gametic level. Gene expression analyses are currently underway to decipher biomarkers for egg/embryo quality at "critical" developmental stages. Overall, our research results show the importance of sperm density, individual male-female parental crosses, and sperm-ovarian fluid interactions for hybrid catfish production. Future research will be discussed in light of these findings.
