To determine the cytotype with better traits for the aquaculture practices of the dojo loach Misgurnus anguillicaudatus from the viewpoint of fish farming improvement, factorial crosses (2n$ 9 2n#, 2n$ 9 4n#, 4n$ 9 2n#, 4n$ 9 4n#) were conducted between natural diploids (D) and tetraploids (T), producing DD, DT, TD, and TT groups (female listed first). The potential benefits of the different cytotypes in culture were evaluated by comparing growth performance and survival rate for a 15-month rearing trial under the same production conditions. The average fertilization rate in DT and TT was significantly lower than in the DD and TD groups, possibly indicating the poor fertilizing capacity of the tetraploid sires. Survival rate in DT and TD was slightly lower than in DD but significantly higher than in the TT groups. Tetraploid females produced obviously larger eggs than diploids and, subsequently, significantly longer initial body length of TT and TD than DD and DT fry. However, from the second month of the growth trial, TT suffered higher mortality than other cytotypes, which significantly influenced morphometric growth parameters. The TD group exhibited superior growth performance throughout the experiment. The mean body length of DT was comparable with that of DD fish during the first 7 months but began to outgrow DD from the 9th month. This study suggests that the relatively better growth of tetraploid and higher survival rate of diploid can be integrated via inter-ploidy hybridization to get TD triploids with better culture traits.Cytotype: individuals of the same species with different cytogenetic composition. Factorial crosses: approach of producing offspring through inter-cytotype and intra-cytotype breeding with all possible crosses.
ABSTRACT. The mandarin fish (Siniperca chuatsi) is a traditionally cultured freshwater fish with high commercial value in China. To facilitate markerassisted selection in genetic improvement of this species, 120 microsatellite markers from the literature were characterized in the 25 largest and 25 smallest individuals. Eighteen polymorphic loci were then used to genotype 200 individuals, and the associations between their genotypes and growth traits were examined. We found that eight genotypes of six loci were positively correlated with growth traits (body weight, length, and height) in the mandarin fish population. The average observed and expected heterozygosities were 0.68 and 0.59, respectively, and the average PIC value was 0.50, indicating a population with high genetic diversity. Therefore, these markers could be useful for assisted selection in genetic breeding of this species and its related species.
To determine the genotype with better traits for aquaculture practices of the loach, factorial crosses were made among diploid (D), tetraploid (T) dojo loach, Misgurnus anguillicaudatus, and large‐scale loach, Paramisgurnus dabryanus (P), producing DD, DT, DP, TD, TT, TP, PD, PT, and PP genotypes (female listed first). The growth performance and survival of different genotypes in culture were evaluated through a 48‐wk rearing trail. The average fertilization rate in genotypes with P. dabryanus as female parental was significantly higher than those of M. anguillicaudatus as female parental. The average fertilization level of sperm from P. dabryanus was about the same as diploid M. anguillicaudatus but significantly higher than tetraploid M. anguillicaudatus. The highest survival rate was found in DD group (52.77%) and PP group (50.31%) (P > 0.05). The intergenetic crosses between P. dabryanus and M. anguillicaudatus, especially for PD (19.05%), DP (17.89%), and PT (15.44%) groups, exhibited poor survival rates. Under the similar rearing conditions, PP group showed significant growth advantage. Growth rates of the interspecific hybrid progenies were found to be intermediate in comparison with the parental species. According to these results, the PP genotype is more suitable for aquaculture practice.
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