Effects of Donor Size, Host and Technician Skill for Success of Xenogenesis for Sturgeon or Catfish Gametogonium Transplantation into Triploid Catfish

Abstract

Xenogenesis is an innovative reproductive technology for the gamete production of biologically and commercially important species. As the primary source of caviar sold commercially, wild sturgeon populations have been experiencing declines linked to over exploitation and habitat alterations. However, cultural and demographic shifts along with increased incomes and the improved availability of premium products is leading to increased customer demand for such luxury products. An increased demand for caviar as well as pressure being placed on natural sturgeon populations provide opportunities to explore xenogenic solutions, specifically the use of ictalurid hosts as surrogates for producing sturgeon gametes. Oogonial and spermatagonial stem cells from two sturgeon species, Siberian sturgeon (Acipenser baerii) and lake sturgeon (A. fulvescens) were isolated and transplanted into white catfish, Ameiurus catus ♀ x blue catfish, Ictalurus furcatus ♂ hybrid catfish and channel catfish (I. punctatus) hosts. Results from this study indicate that there were significant increases in cell area (P = 0.002) and cluster area (P = 0.006) over the sampling points for white x blue hybrid catfish injected with lake sturgeon gametogonium. Moreover, a total of 88.9% of sampled fish displayed fluorescence from dyed donor cells during the post injection sampling period, indicating that the donor stem cells from this biologically important species can successfully proliferate in triploid white x blue hybrid catfish recipients. Although there were no statistically significant increases in cell area (P = 0.702) or cluster area (P = 0.150) in triploid channel catfish transplanted with Siberian sturgeon OSCs, there were still observed increases for both metrics. Furthermore, 76.7% of the triploid channel catfish transplanted with donor Siberian sturgeon OSCs sampled displayed fluorescence during the sampling period, indicating that these cells can survive in triploid channel catfish hosts. The results from the current study suggest that white catfish may be better xenogenic hosts for increasing cell and cluster proliferation compared to channel catfish hosts. A second study investigated the relationship between body size characteristics and live gametogonium quantity for channel catfish (I. punctatus). Xenogenesis is becoming a well-documented technology for overcoming the reproductive barriers to produce the valuable hybrid catfish (channel catfish ♀ with blue catfish ♂). Currently, there are limited resources available for selecting the optimal size donor fish to maximize cell quantity and quality, which is critical to increase the efficiency of xenogenesis procedures. Therefore, a study was conducted to determine the relationships between total length (TL), total weight (TW), and the quantity and quality of extracted gametogonium in channel catfish donors. Relationships were observed between TW and the number of extracted live OSCs (r2 = 0.460; P = < 0.001) as well as the TL and number of live OSCs (r2 = 0.449; P = < 0.001), indicating that an approximate TW of 150 to 350 g and TL of 28 to 38 cm yield the largest quantity of stem cells. Similarly, in males TL (r2 = 0.149; P = < 0.001) and TW (r2 = 0.233; P = < 0.001) revealed a relationship to the number of extracted live SSCs, where 20 to 40 cm and 350 to 600 g males yielded the highest number of extracted live stem cells. These observed relationships are intended to be used as biomarkers to aid in the donor selection process. Lastly, a third study assessed the impact of technical aspects in the xenogenesis procedure on xenogen production by examining the impact of microinjection techniques as well as technician skill level. Although no significant relationships were found between low and high experience classes using the manual or automatic injectors (P = 0.387 and P = 0.369 respectively) and no significant improvements for experience classes as they became more familiar with injection methods after subsequent repetitions (low experience class, manual and automatic, P = 0.362 and P = 0.875 respectively; high experience class, manual and automatic, P = 0.193 and P = 0.086 respectively). This is likely due to highly variable data points, but some trends were observed. Slight improvements were made in both experience classes between their first and final repetitions using the manual injector indicating technicians were becoming more proficient with more experience. Furthermore, slight decreases in injection success were noted for both experience classes using the automatic injector between their first and final repetitions. This potentially stems from blockage issues with the glass needles used in the automatic injecting apparatus. Observations were also made comparing the success of individual technicians. Technicians had higher success rates while using the manual injector compared to the automatic injector (57.5% compared to 49.4%, respectively). The two lowest experience technicians also made notable improvements while using the manual injector and automatic injector, respectively. Technicians’ preference to either injection method was also examined. In 4 of 5 cases, the percentage xenogens produced was very similar between the preferred and non-preferred methods. In one case, the technician preferred the automatic injector but produced almost double the xenogens using the manual injector.