The United States catfish industry is playing a significant role in advancing the national aquaculture industry, coinciding with a cultural shift towards increased consumption of farmed fish. The hybrid catfish (♀ channel catfish, Ictalurus punctatus, × ♂ blue catfish, I. furcatus ) accounts for ~70% of the catfish market due to its superior performance compared to its parent species. To continue advancing the hybrid catfish industry, efforts are being made to advance reproduction techniques such as xenogenesis. Xenogenesis has successfully enabled the production of hybrid catfish embryo by transplanting undifferentiated stem cells derived from donor diploid blue catfish fish into a triploid channel catfish. However, a critical aspect is establishing the ideal quantity of donor cells for transplantation, a factor pivotal for boosting both colonization and proliferation efficiency. Thus, the present study is focused on identifying the optimal quantity of blue catfish stem cells for transplantation to produce xenogeneic catfish. Triploid channel catfish fry were injected with either 80,000 or 100,000 blue catfish stem cells labeled with PKH26 dye from 4-, 5-, and 6-days post-hatch (DPH). Then at 45 and 90 DPH, total length (TL), weight (BW), and survival of recipients were evaluated. Colonization of donor cells in recipients was evaluated using PKH26 dye fluorescence by calculating the percent cell (<150 μm2) and cluster areas (>150 μm2 ) and PCR was used to determine the percentage of xenogens from gonadal tissues.
Quantity of stem cell injected had no overall significant impact on survival (p>0.05) of recipient fish at both sampling periods, but TL (p<0.05) and BW (p<0.05) were significantly different at times which can be explained by stocking density variation. At both sampling intervals, no significant difference was seen for percent cell area fluorescing (p>0.05), but cluster area was found to be significantly higher in individuals injected with 100,000 stem cells (p=0.001 & 0.003). PCR analysis showed, 83.7% and 79.3% of xenogens were detected when recipients were injected 80,000 and 100,000 cells, respectively. O verall, introduction of 100,000 cells/fry led to better proliferation and colonization of blue catfish donor cells in channel catfish hosts. These findings will further enhance the efficiency and feasibility of germ cell transplantation for commercial-scale hybrid catfish production.
Key words: Xenogenesis, Blue catfish, Stem cells, Colonization