昆山市阳澄湖大闸蟹产业研究院项目（HX2021509300）, 中央级公益性科研院所基本科研业务费专项资金项目(2021XT0704), 国家自然科学基金面上项目(31772850) 共同资助。
For revealing the origin difference on the morphological characteristics for a fine structure of cheliped merus, geometric morphological analysis was applied for the first time to comparatively investigate with E. sinensis crabs from seven different well-known geographical origins in Hunan Province, Anhui Province and Jiangsu Province in the middle and lower reaches of the Yangtze River. Based on landmark selection principle of corresponding computer software image processing, a 14-landmark system was established, and then, the average cheliped merus shape of the crabs from the seven origins was obtained by standardized operation. The morphological variation vector was further visualized by thin plate spline analysis and mesh deformation. In comparison with the average cheliped merus shape, although no significant variation was found for that of Wuwei wild population, significant differences were documented for those from other six origins, i.e. the morphology of the merus of crabs from three origins in Anhui Province showed the same trend. The left lower end of the merus was narrowed inward, and the internal depression point of the merus was close to the left lower end. The morphology of the merus of crabs from remaining 3 producing origins of Hunan and Jiangsu Provinces showed the same trend. The left lower end of the merus extended outward, and the internal depression points of the merus shifted to the right upper direction. The discriminant analysis of the above standardized data showed that the discriminant accuracy of female and male crabs could reach 100%. The above results innovatively confirm that the landmark approach has great potential for nonlethal and non-wounded determination of the origin difference and traceability of E. sinensis crabs based on geometric morphology measurement by either large structure of carapace or fine structure/small part of cheliped merus.