Reproductive and genetic capacity of spermatozoa of inter-populational hybrid males in the loach, Misgurnus anguillicaudatus

Abstract

Summary Reproductive capacity was analyzed in inter-populational hybrid males between geographically different populations of the loach Misgurnus anguillicaudatus, which were suggested to be genetically distinct by previous studies. Hybrid males exhibited high percentages of spermatozoa with poor or no motility, when compared with wild type diploid males. Sperm volume was apparently less than that from wild type. Scanning electron microscopy (SEM) revealed that spermatozoa of hybrid males showed abnormal morphology such as no flagellum, double or more flagella, ill-developed mid-piece and significantly larger head sizes. Three different cell populations with haploid (1C), diploid (2C) and tetraploid (4C) DNA content were flow-cytometrically detected in sperm samples collected from hybrid males, whereas diploid males showed only haploid spermatozoa. Fertilization of eggs of wild type females with sperm of hybrid males gave very few diploid and triploid survivors. Microsatellite analyses showed that haploid spermatozoa of hybrids were produced by meiotic segregation, while diploid spermatozoa were formed by unreduced spermatogenesis. The present results showed that inter-populational loach hybrid males were almost sterile, but a few fertile haploid and diploid spermatozoa were generated. Such traits of inter-populational hybrid males are similar to those reported in inter-specific hybrids. Hybridization disrupted regular meiosis and normal spermatogenesis in the loach from the cross between different