Meiotic chromosome configurations in triploid progeny from reciprocal crosses between wild-type diploid and natural tetraploid loach Misgurnus anguillicaudatus in China

Abstract

Here, we showed meiotic chromosome configurations prepared from oocyte germinal vesicles and spermatocytes of triploid loaches produced from reciprocal crosses between wild-type diploids (2n = 50) obtained from Dalian, Liaoning Province, China and natural tetraploids (4n = 100) from Chibi, Hubei Province, China. Major meiotic cells in triploids comprised 25 bivalents and 25 univalents, but cells with one to five trivalents were also observed. When three homologous chromosomes bearing nucleolar organizing regions (NOR) were identified with the detection of signals or positive sites by silver staining, chromomycin A 3 staining and fluorescence in situ hybridization with a 5.8S ? 28S rDNA probe, two third of selected triploid cells gave a configuration including one bivalent with two NORs (association of two homologous chromosomes) and one univalent with one NOR. However, other triploid cells showed three univalent each of which had one NOR, suggesting a failure of synapsis between homologous chromosomes. These results suggested that triploid female and male should produce aneuploid gametes with the theoretical mode at 1.5n (37 or 38 chromosomes).

Aneuploid progenies of triploid hybrids between diploid and tetraploid loach Misgurnus anguillicaudatus in China

“…22IIs ? 3IIIs and so on (Li et al 2015). In our previous study, we also reported failure of synapsis between homologues and thus formation of gametes with unbalanced genetic materials was also predicted (Li et al 2015).…”

“…3IIIs and so on (Li et al 2015). In our previous study, we also reported failure of synapsis between homologues and thus formation of gametes with unbalanced genetic materials was also predicted (Li et al 2015). Hamphrey (1950, 1954) observed a shift toward the lower chromosome numbers in diploid 9 triploid axolotl progenies and suggested that this was caused by the elimination of some lagging chromosomes and the resultant failure of gametogenesis in gametes with higher numbers of extra chromosomes.…”

“…The 1.5n gametes can be predicted by equal segregation of 25IIs formed by 25 pairs of homologous chromosomes and random assortment of the extra 25Is of 75 chromosomes in triploid, according to the binominal distribution previously reported by Zhang and Arai (1999) and Li et al (2015). In the 3n 9 3n-3 Chromosome distributions in progenies from 2n 9 3n-3 (a), 3n 9 2n-3 (b) and 3n 9 3n-3 (c) crosses using the triploid hybrids (diploid female 9 tetraploid male).…”

“…Triploid hybrids were reciprocally produced between tetraploids from Hubei Province, China and diploids from Liaoning Province, as previously described in Li et al (2012Li et al ( , 2013Li et al ( , 2015. Using two females and two males selected from each triploid (tetraploid females 9 diploid males) hybrid, diploid, and tetraploid brood-stock, we produced the two sets (nos.…”

“…Since we observed that meiotic cells most frequently exhibited 25IIs and 25Is in triploid hybrids, we predicted the formation of gametes with a mode at 1.5n (37 or 38) chromosomes as a result of equal segregation of 25IIs and random segregation of 25Is (Li et al 2015).…”