Reproductive capacity of triploid loaches obtained from Hokkaido Island, Japan

Abstract

Reproductive capacity was investigated in naturally occurring triploid individuals of the loach Misgurnus anguillicaudatus collected from Memanbetsu Town, Abashiri County, Hokkaido Island, Japan. These triploids have been considered to appear by accidental incorporation of the haploid sperm genome from normal diploid into unreduced diploid eggs from the clonal lineage that usually reproduces unisexually. By fertilization with sperm from the normal male, one triploid female gave many inviable aneuploid (2.1-2.7n) and very few tetraploid progeny, whereas the other produced both diploid and triploid progeny. The results suggest that at least four different types of eggs can be formed in triploid females in this locality. In contrast, no progeny hatched when eggs of the normal female were fertilized with sperm or sperm-like cells obtained from triploid males. These gametes exhibited inactive or no motility after adding ambient water. They had larger head sizes than those of normal haploid sperm and had a short or no tail. Although their ploidy was triploid or hexaploid, a small number of haploid cells were detected in the semen by flow cytometry. Thus, triploid males were generally sterile, but they have a little potential for producing very few haploid sperm.

Simultaneous Mendelian and clonal genome transmission in a sexually reproducing, all-triploid vertebrate

“…In the present paper, we performed sibship analyses with 15 co-dominant microsatellite loci to evaluate genome-wide clonal (males absent), restricted to reptiles [7,8]; Sperm-dependent parthenogenesis (i.e. gynogenesis): clonal, embryogenesis requires trigger from allospecific sperm that is not incorporated (rare 'paternal leakage' might incorporate subgenomic amounts of paternal DNA), occurs in teleost fishes and urodelan amphibians [9]; Kleptogenesis: females acquire full or partial genomes from their mates by a not fully understood mechanism, allowing them to purge genomes from deleterious alleles (here BB); described from urodelan amphibians [10]; Unnamed form of hybridogenesis: clonal diploid eggs are fertilized by sperm from a recombining sexual species that can be diploid or triploid (as in meiotic hybridogenesis); occurs in anuran amphibians and teleost fishes [11][12][13]; Meiotic hybridogenesis: may occur in triploid males and/or females; found in teleost fishes and anuran amphibians [14,15]; ploidy elevation of the diploid offspring, which might produce diploid hybrid gametes, can occur in the next generation (becoming then e.g. ABB 0 ) to restore triploidy (similar to preceding form of hybridogenesis); Pre-equalizing hybrid meiosis: occurring in Batura toads: Both sexes are triploid and exhibit Mendelian segregation and recombination in the B genomes (equivalent to NORþ; this paper), while the A genome (i.e.…”

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

“…Thus, some hybrids mainly produce haploid eggs together with diploid, aneuploid, and other unusual eggs. The simultaneous appearance of various ploidy-types of eggs has been reported in natural triploids and diploid-triploid mosaics, accidentally derived from a natural clonal lineage of the loach (Oshima et al, 2005;Yoshikawa et al, 2007). Similar observations of simultaneous formation of different types of eggs were reported in triploid (diploid x tetraploid) loach (Matsubara et al 1995;Arai andMukaino, 1997, 1998;Momotani et al, 2002), spontaneous triploid in central area of Honshu Island, Japan (Zhang and Arai, 1999) and other triploid teleosts including minnow in the genus Squalius (Alves et al, 2004) and Phoxinus (Dawley and Goddard, 1988;Goddard and Dawley, 1990).…”

“…Clonal diploid loaches produce genetically identical diploid eggs, most of which develop to clonal diploids by gynogenetic activation with sperm of bisexually reproducing diploid males, but some eggs develop to triploids and diploid-triploid mosaics due to the infrequent incorporation of a sperm nucleus before and after cleavage, respectively (Morishima et al, 2002;Itono et al, 2006Itono et al, , 2007. A majority of such clone-derived triploid females were reported to produce fertile haploid eggs (Oshima et al, 2005;Morishima et al, 2008b), but males are sterile (Oshima et al, 2005). Diploid-triploid mosaic individuals revealed more complicated reproductive modes; diploid-triploid mosaic males generate fertile diploid sperm with genetically identical clonal genotypes (Morishima et al, 2004), whereas mosaic females produce haploid, clonal diploid and triploid eggs, simultaneously (Yoshikawa et al, 2007).…”

Detection of hybridization between two loach species (Paramisgurnus dabryanus and Misgurnus anguillicaudatus) in wild populations

“…3). Natural triploids of pond loach were found in Japan (Oshima et al 2005). The triploid males were generally sterile and showed little potential to produce haploid sperm, while the triploid females were fertile and laid a large triploid egg and a normal-size haploid egg (Matsubara et al 1995;Oshima et al 2005).…”

“…Natural triploids of pond loach were found in Japan (Oshima et al 2005). The triploid males were generally sterile and showed little potential to produce haploid sperm, while the triploid females were fertile and laid a large triploid egg and a normal-size haploid egg (Matsubara et al 1995;Oshima et al 2005). Viable reciprocal diploid and triploid hybrids between mud loach, Misgurnus mizolepis (2n=48) and pond loach, M. anguillicaudatus (2n=50) were also recorded in South Korea (Kim et al 1995), in which diploid hybrids (2n=49) were fertile, and triploid hybrids (2n=74), with two sets of pond loach and one set of mud loach chromosomes, were sterile in both sexes (Nam et al 2004).…”