罗氏沼虾养殖群体表型性状间的相关性及类群差异分析

为研究罗氏沼虾(Macrobrachium rosenbergii)养殖群体表型性状间的相互关系及不同类群间的性状差异,本研究对人工养殖的罗氏沼虾雌、雄及“老头虾”3个类群共490个个体的体重、体长、全长等12个表型性状进行了相关分析、形态性状对体重影响的通径分析等。结果表明, 3个类群除上、下额刺数2个可数性状外,其他9个可量形态性状与体重都呈极显著的正相关(P<0.01);影响体重的关键形态性状在3个类群中各不相同,但体长、头胸甲长、第二步足长在3个类群中均是影响体重的关键指标;分别建立了各类群体重与关键形态性状的多元回归方程。聚类分析和主成分分析结果表明,雌、雄2个类群表型上更为相似,“老头虾”与雌性个体的差异最大。腹部轮廓特征(包括腹长、腹宽、腹高)、全长、体长及第二步足长对3个类群的差异贡献较大。雌性个体腹部发达,“老头虾”则第二步足尤为发达。本研究结果可为罗氏沼虾的选择育种、基础生物学及行业标准的制定提供数据资料。

Correlation and difference of phenotypic traits among cultured groups of the giant freshwater prawn Macrobrachium rosenbergii

The giant freshwater prawn (GFP) Macrobrachium rosenbergii is one of the largest freshwater shrimps in the world, widely distributed in the tropical and subtropical regions of Southeast Asia, the Indian Ocean, and the Pacific Ocean. It has become an important cultured species in China since its introduction because of its wide diet, high growth rate, and high economic value. However, the GFP shows slower growth and poor resistance primarily resulting from an inbreeding depression and farming at high density. One male morphotype named as "old males" or "old blue claw" is present commonly among blue claw males, exhibiting developed second legs and carapace with a dark blue body color, and its economic value is very low. Therefore, improved varieties are urgently needed through selective breeding. The body weight is one of the most important traits for selective breeding, which are closely correlated with morphometric traits. To investigate the correlation and differences in phenotypic traits among cultured groups of M. rosenbergii, a correlation analysis among 12 phenotypic traits, stepwise multiple regression, and path coefficient analysis on body weight and morphometric traits were performed on 490 individuals of M. rosenbergii selected from Jiangsu Shufeng Prawn Breeding Co. Ltd. representing three cultured groups:females, males, and old males. Compared with the phenotypic traits in the industry standard published in 2002, the growth performance of the present GFP variety has been greatly improved after years of breeding, and a new industry standard for the new variety should be developed and published. The results of correlation analysis and path analysis showed that 1) except for numbers of dorsal and ventral rostrum teeth, the coefficients between the other nine traits and body weight showed extremely significant positive correlations (P<0.01); 2) the key morphometric traits attributed to body weight were different in different groups, but body length, carapace length, and length of second leg were the key traits in the three groups. We estimated the multiple regression equations for each group according to the key traits. For each group, the direct effect of each key morphometric trait on body weight was less than the total indirect effects through the other key traits. The hierarchical cluster analysis and principal component analysis showed that females and males clustered together, and their morphometric traits were similar; the highest variation existed between females and old males. Abdominal characters (including abdominal length, abdominal width, and abdominal depth), total length, body length, and length of second leg contributed the most to the differences among the three groups. Among the three groups, females show advantages in the growth of the abdomen, whereas old males have more developed second legs. The present study can provide data for reference not only for the selective breeding of M. rosenbergii but also for its basic biology and the development of industry standard.