Induction of meiotic gynogenesis in Lanzhou catfish (Silurus lanzhouensis) with heterologous sperm and evidence for female homogamety

As a critical factor in the sustainability of fisheries, gynogenesis can be used to provide a shortcut for the genetic improvement of the endangered and degraded germplasm resources of the important Yellow River fish Silurus lanzhouensis. In this study, ultraviolet-inactivated yellow catfish Pelteobagrus fulvidraco sperm were used to induce meiotic gynogenesis in S. lanzhouensis through cold shock, and the optimal conditions for the genetic inactivation of the sperm and cold shock treatment were selected. Using microsatellite markers and gonadal histology, the genetic purity and sex determination of the gynogenetic offspring of S. lanzhouensis were analysed. The optimal induction conditions were as follows: treatment with P. fulvidraco sperm with 107- mu W/cm(2) ultraviolet irradiation for 30 min, fertilization of S. lanzhouensis eggs for 6 min and subsequent cold shock treatment at 4-6 degrees C for 25 min. Flow cytometry and microsatellite markers confirmed the successful induction of meiogynogenesis. The homozygosity of the gynogenetic group (0.63) was higher than that of the normal control group (0.32). The sex ratio was determined through gonad histological observations, and 100% of the offspring in the gynogenetic groups were female, strongly indicating that the sex determination system of S. lanzhouensis is the XX/XY-type. In this study, inactivated heterologous sperm were used to successfully obtain meiogynogenetic individuals of S. lanzhouensis, and the study provides an important basis for the establishment of a pure line of these endangered fish and sex-controlled breeding of S. lanzhouensis.