| Siniperca chautsi and S. scherzeri are both valuable freshwaterfishes which are only distributed in East Asia. The fertilized eggs ofSiniperca scherzeri♀×S. chuatsi♂F1were obtained with artificialmanipulation aimed to improve the performance of their breeding. Inorder to provide basic data for the study of crossbreeding of mandarinfish, we study the biological characteristics of hybrid F1on embryonicdevelopment, morphological characteristics and expression of somemuscle growth-related genes. The growth of skeletal muscle fibers atdifferent developmental stages was also observed by paraffin sections.The embryonic development characteristics were recorded underlight microscopy and larval body length were measured daily. Resultsshowed that the fertilized eggs was2.20±0.09mm in diameter, half offertilized eggs were hatched out at67hours after fertilization in flowingwater with temperature varying from18℃to25℃. The wholeembryonic development of the hybrid F1underwent the cleavage stage (7hours), blastula stage (8hours), gastrula stage (8hours), neural stage(4hours) and organogenesis stage (40hours). The newly hatched larvaeof the hybrid F1was4.12±0.12mm in length, and the average dailygrowth rate was1.03mm/d from0to43hatching days. The embryonicdevelopment of the hybrid F1was intermediate to their parents, and thegrowth rate at post embryonic stage was similar to that of its paternalfish.The morphological characterization of the hybrids F1wascompared with their parents in body spots, meristic and morhometricparameters. Results showed the hybrids F1resembled to the femaleparents in body spots but resembled to the male parents in body shape.The numbers of dorsal fins, anal fins, pectoral fins and pelvic fins wererelatively consistent in these three populations. The uplift angle at theposterior head and anterior dorsal part in the hybrids F1was moreobviuos than the female parents. The hybrids F1showed a mediatedtype between the female and male parents in trunk longitudinal axis,vertical axis, and dorsal/ventral ratio, respectively. Euclidean distancecluster analysis showed S. scherzeri formed a independent group,whereas the hybrids F1formed another group with S. chuatsi. Thediscriminating accuracy rate for S. scherzeri, S. chuatsi, F1was100%,81.8%,85.2%, respectively. The hybrids F1lied between S. scherzeriand S. chuatsi, and tended to S. chuatsi in discriminating scatterplot analysis.we got muscle samples of Siniperca chuatsi♂×S. scherzeri♀F1and their parents at five developmental stages in90days afterhatching. The skeletal muscle growth characteristics were identified by numbers and diameters of muscle fibers through paraffin sections. Meantime, the mRNA expression of myostatin, MyoD, myogenin in muscle was detected by quantitative PCR. The results showed there were significant differences in growth among three mandarin fish. Siniperca chautsi grow fastest, F1secondly and S. scherzeri the last. At different developmental stages, numbers of muscle fibers in three mandarin fish showed no significant difference,while the average diameters of the muscle fibers showed positivecorrelation with growth rate. Growth differences among three mandarin were mainly caused by muscle hypertrophy. The myostatinmRNA expression peak appeared in D20, then the expression showed a downward trend. MyoD mRNA expressed highly in D10,D20and decreased in following days. The myogenin mRNA expression was the lowest in D20, followed by an obviously increasein Siniperca chuatsi, and F1secondly, while S. scherzeri stable. Itshowed correlations between muscle growth and gene expressionin three mandarin at different growth stages. |
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