Hybrid Male Sterility between the Fresh- and Brackish-water Types of Ninespine Stickleback Pungitius pungitius (Pisces, Gasterosteidae)

Abstract

-Two ecologically distinct forms, fresh-and brackish-water types, of ninespine stickleback coexist in several freshwater systems on the coast of eastern Hokkaido. Recent genetic analyses of 13 allozyme loci revealed genetic separation between the two types even though their spawning grounds were in close proximity. On the other hand, there is only a small difference in mitochondrial DNA (mtDNA) sequence between the two types suggesting that they diverged quite recently or that mtDNA introgression occurred between them. To test for postzygotic reproductive isolating mechanisms and hybrid mediated gene flow, we examined the viability and reproductive performance of reciprocal F 1 hybrids. The hybrids grew to the adult size normally and both sexes expressed secondary sexual characters in the reciprocal crosses. The female hybrids were reciprocally fertile, while the male hybrids were reciprocally sterile. Histological and flow-cytometric analyses of the hybrid testis revealed that the sterility pattern was classified as 'gametic sterility,' with gonads of normal size but abnormal spermatogenesis. To our knowledge, the present finding is a novel example of one sex hybrid sterility in the stickleback family (Gasterosteidae).

Heteromorphic sex chromosomes in the ninespine stickleback Pungitius pungitius

“…Such male‐related chromosomal polymorphism indicated an XX–XY sex chromosomal determination system in the P. pungitius . Although the existence of an XX–XY system in the P. pungitius has been proposed (Takahashi et al , 2005), this is the first report describing morphologically differentiated X and Y sex chromosomes in this species. The absence of a cytogenetically visible Y chromosome in the P. pungitius sampled in brackish coastal waters in North America and Europe (Chen & Reisman, 1970; Klinkhardt & Buuk, 1990) might result from differences in the techniques used in the previous and current studies.…”

A phylogenomic perspective on diversity, hybridization and evolutionary affinities in the stickleback genusPungitius

“…Third, current understanding of phylogenetic relationships in the Pungitius species complex resides heavily on mitochondrial DNA sequences (e.g., Bae & Suk, 2015;Takahashi & Goto, 2001;Teacher, Shikano, Karjalainen, & Merilä, 2011;Wang et al, 2015), and only a few studies-all based on either limited geographical or taxon sampling-have utilized nuclear genetic information (Aldenhoven, Miller, Corneli, & Shapiro, 2010;Bae & Suk, 2015;Haglund et al, 1992;Natri, Merilä, & Shikano, 2019;Shikano, Ramadevi, Shimada, & Merilä, 2010;Takahashi et al, 2016;Takata, Goto, & Yamazaki, 1987b;Wang, Shikano, Persat, & Merilä, 2017). Phylogenetic studies based on a large number of nuclear loci are motivated by the well-known limitations of phylogenetic and phylogeographical inferences based on mitochondrial information (e.g., Ballard & Whitlock, 2004;Hey & Machado, 2003;Toews & Brelsford, 2012), as well as by the evidence for weak post-zygotic isolation (Kobayashi, 1959;Takahashi, Nagai, & Goto, 2005;Tsuruta & Goto, 2006;Ziuganov & Gomeluk, 1985), and hybridization in this genus (Denys et al, 2018;Niwa, 1987;Takahashi et al, 2016;Takahashi & Takata, 2000;Wang et al, 2017;Natri et al, 2019).…”

Male Hybrid Sterility in the Mule Duck is Associated with Meiotic Arrest in Primary Spermatocytes

“…Reproductive isolation mechanisms that restrict gene flow between different species can be categorized into two main types: one is the prezygotic (before the formation of zygotes/before fertilization) isolation mechanism, which prevents the eggs from being fertilized by the sperm of different species by gamete isolation due to gametic incompatibility and the environmental/ spatial and behavioral isolation of two populations; and the other is the postzygotic (after gamete fusion) isolation mechanism, which prevents the formation of fertile offspring after fertilization (Wu and Palopoli, 1994). When animals of genetically diverged populations hybridize, the resulting hybrids exhibit various abnormalities in development and/or reproduction, being lethal or sterile depending on the combination of parental species (Forejt and Iványi, 1974;Iwamatsu et al, 1984Iwamatsu et al, , 1986Iwamatsu et al, , 2003Matsuda et al, 1991;Hale et al, 1993;Sakaizumi et al, 1993;Yoshiki et al, 1993;Shimizu et al, 1997;Safronova et al, 1999;Elliot et al, 2001Elliot et al, , 2004Takahashi et al, 2005;Borodin et al, 2006;Sakai et al, 2007;Oka et al, 2010). Postzygotic barriers such as hybrid inviability, sterility, and/or breakdown (F 1 hybrids are viable and fertile while further hybrid generations such as F 2 and backcrosses are inviable or sterile) ensure reproductive isolation for fixing and maintaining species by preventing hybrids from passing their genes to the other population.…”