Effect of Seasonality for Optimization of Germ Cell Extraction from Mature Blue Catfish

Abstract

Xenogenesis is an innovative tool for hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) seed production, accomplished by transplanting undifferentiated germ cells derived from a donor diploid fish into a sterile recipient, which then enables recipient fish to produce donor‐derived gametes. There is potential to collect donor‐derived germ cells from mature fish during certain times of the year depending upon seasonal temperature and serum sex steroid hormonal fluctuations. The objective of this study was to evaluate seasonal variations in germ cell counts and serum sex steroid hormonal profiles in mature Blue Catfish. Mature fish were collected monthly over the full annual cycle to quantify the number of live germ cells (spermatogonia A, oogonia), viability of germ cells, and levels of serum sex steroid hormones, including testosterone, 11‐ketotestosterone, and 17β estradiol. Extracted spermatogonia A counts were highest from April to June, whereas a significant decline was detected from July to November. Extracted live oogonia counts were highest in April and gradually decreased to zero over the months of May to August. Seasonal variations in serum testosterone, 11‐ketotestosterone, and 17β estradiol followed a similar pattern as the live spermatogonia A and oogonia counts. Even though spermatogonia A counts were relatively lower in mature than in immature Blue Catfish males, extracting spermatogonia A from mature Blue Catfish males during April to June provides an added advantage to the process of artificial fertilization, as it is required to sacrifice these fish to collect sperm.

Advancing aquaculture: Production of xenogenic catfish by transplanting blue catfish (Ictalurus furcatus) and channel catfish (I. punctatus) stem cells into white catfish (Ameiurus catus) triploid fry

“…The potential of hybrid catfish embryo production through xenogenesis has been highlighted in the literature by transplanting BSCs into a triploid channel catfish host [12,[15][16][17]. However, having a surrogate with a short maturation time and a smaller body size than channel catfish would be ideal for commercial applications.…”

“…Fuller's earth solution was prepared by adding 6 g of powdered Fuller's earth to 1 L of pond water. After 3 min, triploid induction was carried out according to standard protocols [12,[15][16][17]. Briefly, the fertilized eggs were transferred into a steel chamber and after an additional 2 min hydrostatic pressurize was applied at 7,000 PSI for 5 min.…”

“…After transplantation, these cells can migrate, colonize and proliferate, giving rise to female or male germ cells, after which the gonad differentiates into an ovary or a testis, depending on the hosts' genetic sex [14]. Due to these unique characteristics, significant work has been devoted to transplant blue catfish SSCs and OSCs for xenogenic applications to support hybrid catfish production [12,[15][16][17].…”