Study On Cytogenetic In Hybrid Triploid Loach Misgurnus Anguillicaudatus

Loach (Misgrunus anguillicaudatus) is a kind of small fish, which is popular with consumers due to highnutrition contained. However, since natural survival environments of loach were destroyed, and over-fishing,the productions and qualities of nature loach decline gradually, it is difficult to meet the need of markets. So, itis necessary to breed advantage property of new variety and do some researches on the respects of cytogenetics.Polyploidy phenomenon was found in loach, there are not only diploid loaches, but also triploids andtetraploids. The researches on triploid fish are becoming a hot point due to some excellent features, such aspoor fertility, high rate in growth and so on. Whereas the researches are mostly focusing on aspects of somaticchromosomes, no reports on meiotic chromosome, especially the respects of behavior and bandings werefound in hybrid triploid loach in China. In this study, hybrid triploid loaches from2n x4n and4n x2n wereselected for the research, which focused on the behavior and bandings of meiotic chromosomes, bandings wereobtained by Ag-NORs、CMA3/DA/DAPI and FISH. At last, we also performed the research on C banding ofembryonic chromosomes in diploid and triploid loaches, the results showed as bellows:1, No matter the hybrid triploid loaches from2n x4n or4n x2n, Univalents and bivalents were all foundin meiosis of spermatocytes or oocytes, but no trivalent was observed; what is more, the phenomenon ofduplications of genomes was also detected; in testis, both two kinds of progenies of4n x2n and2n x4ncontain polyploid cells from hyper-diploid cells to hypo-triploid cells (23.3%,17.2%) respectively, triploidcells (26.0%,50.9%), from hyper-triploid cells to hypo-tetraploid cells (37.6%,26.4%). Besides few numbersof polyploid cells from tetraploid to hyper-hexaploid cells (3%,5.5%) are found; in ovary, there were alsodifferent numbers of hypo-triploid cells (12%,5.9%), eutriploid cells (80%,86.3%) and cells fromhyper-triploid to hypo-tetraploid cells (8%,7.8%).2, The number of Ag-NORs in chromosomes during meiosis I of spermatocytes showed polymorphism inhybrid triploid loach, two Ag-NORs were found, but some located on one terminal of a univalent and abivalent respectively; and some located on two terminals of a bivalent, situation of three Ag-NORs was alsoobserved, located on two terminals of a bivalent and one terminal of a univalent, but two obvious signals andone faint signal; there was only one Ag-NORs found, located on one terminal of a bivalent, and no Ag-NORsexist on other terminal of the bivalent. The result of CMA3/DA/DAPI showed that polymorphism also exist, two positive signals were observed, located on one terminal of a univalent and a bivalent respectively, orlocated on two terminals of a bivalent. Moreover, FISH signals showed polymorphism in a certain degree, twosignals was observed, located on one terminal of a univalent and a bivalent respectively; but there were alsooccurrence of three signals, located on one terminal of three univalent respectively.3, The result of C bandings in embryonic chromosomes of diploid and triploid loaches show that, thekaryotype of diploid loach was2n=50=10M+4SM+36T, and the karyotype of triploid loach was3n=75=15M+6SM+54T; C bandings were black, compared with other areas, and classified into type of terminalsand centromeres, but no middle type of arm was observed; no matter in diploid or triploid loaches, the type ofterminals were located on terminal of short arm of M1, whereas, compared with the type of centromeres,bigger and more obvious C banding was found on terminal of short arm of M1, and diploid loaches possesstwo pairs of the type of terminal, three pairs in triploid loaches.