Impacts of Host, Cell Density, and Timing of Injection on Efficiency for Xenogen Production in Ictalurid Catfish

Optimization of xenogenesis for hybrid catfish (♀ channel catfish, Ictalurus punctatus × ♂ blue catfish, I. furcatus) embryo production was the goal. The effect of density of unsorted gonadal cells (80,000, 100,000, or 120,000 cells/fry) from blue catfish (BGCs) injected into triploid channel catfish surrogates, and BGCs or channel catfish (CGCs) into triploid white catfish (Ameiurus catus) surrogates on proliferation and colonization rates in surrogates injected at 4-, 5-, or 6-days post-hatch (DPH) was evaluated. At 45 and 90 DPH, survival and size of surrogates, and colonization/proliferation of donor cells (cell area < 150 μm² and cluster area > 150 μm²) were evaluated. Survival and size of all surrogate species were not impacted by cell density or donor. All surrogate species injected with 100,000 cells/fry had larger cluster cell areas than those injected with 80,000 cells/fry. White catfish surrogates with BGCs and CGCs had larger cell areas when injected with 100,000 cells/fry than those injected with 80,000 cells/fry. Both cell and cluster area increased by 90 DPH for all surrogates. PCR and PKH26 red fluorescence analysis confirmed that > 89% and > 86% of surrogates were positive xenogens at 45 and 90 DPH, respectively. No surrogate type or donor was superior to the others regarding colonization and proliferation, survival or growth, thus, channel catfish or white catfish were equally effective surrogates. Potential advantages of white catfish are small size, early sexual maturity, and spawning early in the season. These findings enhance the efficiency of germ cell transplantation for commercial hybrid catfish production.