Xenogenesis, a form of reproductive stem cell-based surrogacy, is an emerging technology for increasing farmed fish production and reducing overharvesting of overexploited fish populations. For the catfish industry in the United States, xenogenesis is a sustainable method to produce the hybrid catfish (channel catfish, Ictalurus punctatus ♀ × blue catfish, I. furcatus ♂). Traditionally, xenogenic catfish we re produced using immature germ stem cells (spermatogonial stem cells or oogonial stem cells) derived from an immature donor of a different species and transplanted into sterile surrogates. The gonads of these donor individuals can essentially be ’cloned’ and multiplied into large populations through xenogenesis, allowing mating of superior combining pairs for perpetuity without inbreeding, to maximize performance of hybrid progeny. However, a major limitation of this method is that brooders with the highest combining ability are only identifiable at sexual maturity. By this time, their isogenic gonadal stem cell count is low, reducing the number of xenogenic offspring that can be produced. Thus, alternative methods for producing xenogenic catfish are needed . The objective of this study was to explore new donor cell options , beyond gonadal stem cells, for transplantation into sterile surrogates for the creation of xenogenic catfish.
Triploid channel catfish and white catfish (Ameiurus catus ) surrogates were injected with fresh or cryopreserved kidney, spleen, intestine, skin, or gonadal cells at 5 days post-hatch (DPH). At 45 and 90 DPH, survival, total length, body weight, and colonization of donor cells (measured by percent cell area [<150 μm²] and cluster area [>150 μm²]) of xenogenic catfish were assessed. PCR and PKH26 fluorescent imaging analysis determined the percentage of xenogens from gonadal tissues harvested from surrogates. Results indicated that kidney, spleen, and traditional gonadal cells are viable donor cell options , while skin and intestine cells are not (p < 0.05). Donor gonadal cells outperformed kidney cells, and both gonadal and kidney cells outperformed spleen cells (p < 0.05). Fresh cells outperformed cryopreserved cells across all donor tissue types and surrogate survival (p < 0.05). Surrogate performance did not differ between channel catfish and white catfish (p > 0.05). These results suggest kidney cells are a promising future donor cell source for the creation of xenogenic catfish, with spleen cells showing potential. Cryopreservation is also a feasible method, though with some limitations. Expanding the range of donor cell sources for transplantation may increase efficiency, improve consistency, reduce the number of donor fish needed to produce xenogenic hybrid catfish, and allow us to create generations of populations with fixed combining abilities.