Disruption of normal meiosis in artificial inter-populational hybrid females of Misgurnus loach

Abstract

Artificial cross between two genetically different populations of JapaneseMisgurnus loach was made to examine the reproductive capacity of the artificial inter-populational hybrid females. Ploidy status and microsatellite genotypes of the eggs laid by these hybrids were inferred from those determined in progenies developed by normal fertilization with haploid loach sperm, induced gynogenesis with UV-irradiated goldfish sperm and/or hybridization with intact goldfish sperm. Some hybrid females laid unreduced diploid eggs genetically identical to the mother. However, these diploid eggs could not develop by spontaneous gynogenesis, but grow to triploid by incorporation of a sperm nucleus. Other hybrid females laid haploid eggs together with diploid eggs and/or various aneuploid and polyploid eggs. Thus, a disruption of normal meiosis occurred in inter-populational hybrid females. The results suggested that the two populations should be so distant as to give rise to atypical formation of unreduced and other unusual eggs in their hybrids.

Hybrid origin of gynogenetic clones and the introgression of their mitochondrial genome into sexual diploids through meiotic hybridogenesis in the loach, Misgurnus anguillicuadatus

“…However, in the inter-populational (or inter-clade) Misgurnus hybrids, females might have generated genetically identical unreduced eggs to recover fertility, and very few such eggs might have acquired the developing mode of gynogenesis through mutation for clonal reproduction. The unreduced diploid egg formation was reported in inter-populational M. anguillicaudatus hybrids between group A and B-1, as inferred from mtDNA-CR sequences (Arias-Rodriguez et al, 2009). Recently in the genus Cobitis spinous loaches, clonality and polyploidy were artificially synthesized by hybridization: F 1 hybrids between two bisexual species produced unreduced eggs, a few of which initiated gynogenesis in nature (Choleva et al, 2012).…”

“…It is also been shown that inter‐populational Misgurnus hybrids derived from genetically different groups are generally sterile or undergo unusual reproduction. Experimental Misgurnus hybrids from groups A and B‐1 produce a small number of haploid eggs, a large number of unreduced diploid eggs, and other genetically abnormal eggs, including aneuploids and mosaicisms (Arias‐Rodriguez et al, ). The inter‐populational male hybrids generated a very small number of fertile haploid or/and diploid spermatozoa (Arias‐Rodriguez et al, ).…”

“…Recent molecular phylogenetic studies on Misgurnus from the Far Eastern region of Russia also suggested the presence of different species within M. anguillicaudatus (Perdices et al, 2012). Disruption of normal meiosis and subsequent gametogenesis was also reported in inter-populational M. anguillicaudatus hybrids between group A females and group B males as in atypical reproduction occurred in inter-specific hybrids: most hybrids generated unreduced diploid and other types of unusual gametes (Arias-Rodriguez et al, 2009. All these studies support the hybrid-origin theory for the occurrence of gynogenetically reproducing clones in nature.…”

Reproductive capacity of neo-tetraploid loaches produced using diploid spermatozoa from a natural tetraploid male

“…Consequently, reproductive capacity of the resultant progeny from neo-tetraploid males may be determined by pairing capacity between two chromosomes transmitted from the ancestral tetraploid and those from wild type diploid individuals. In Misgurnus loaches, disruption of normal meiosis and gametogenesis has been reported in inter-specific hybrids (Fujimoto et al, 2008) and sometimes in inter-populational hybrids between genetically distinct groups (Arias-Rodriguez et al, 2009). Genetic difference between ancestral natural tetraploid loach with unknown origin and wild type diploid loach collected from central or southern Hokkaido, Japan (Morishima et al, 2008a) may involve the expression of fertility or sterility in neo-tetraploid loach and its progeny, because these are presumably regarded as being hybrids that lie between different genotypes.…”

The occurrence of hypertetraploid and other unusual polyploid loaches Misgurnus anguillicaudatus among market specimens in Japan

“…Inter-populational hybridization between genetically different groups in M. anguillicaudatus resulted in disruption of regular meiosis and normal gametogenesis, causing formation of unreduced diploid and other unusual aneuploid and polyploidy eggs in females [17] and sterility in males [18]. Molecular genetic relationship between Japanese and Chinese loach populations is still fragmentary and inconclusive, and it is impossible to distinguish them based on morphological characteristics.…”