The first case of gynogenesis induced by cold- and heat-shock treatment in Thamnaconus modestus

Gynogenesis is an effective technique for establishing homogeneous lines and confirming potential chromosomal mechanisms of sex determination in fish. The objective of this study was to induce meiotic gynogenesis in Thamnaconus modestus through the application of cold-or heat-shock treatment, with the ultimate goal of establishing a foundational population to enhance breeding outcomes. Firstly, we obtained the optimal dosage of ultraviolet irradiation (55 mJ/cm2) required to render the sperm genome inactive while still allowing egg activation without any contribution of genetic material to the progeny. After fertilization with the inactivated sperm, diploidization was achieved through either cold-shock (12 degrees C for 45 min) or heat-shock (38 degrees C for 1 min), which suppressed the extrusion of the second polar body. Gynogenetic offspring were confirmed through gen-otyping using 12 microsatellite markers with parental specificity. The heterozygosity of meiotic gynogenesis group decreased by 35.14% when analyzed using SNP markers through whole genome resequencing technique, compared with the wild populations. Overall, the meiotic gynogenetic families were successfully induced, and this is the first protocol described for the induction of gynogenesis in T. modestus, which establishing a complete method of meiotic gynogenesis induction. The procedure described herein may be used to produce a clonal line of fish or for the breeding of improved varieties of T. modestus and other related species.