MORPHOMETRICAL STUDIES ON 10 POPULATIONS OF HELICE TIENTSINENSIS AND H. LATIMERA (CRUSTACEA, DECAPODA) FROM COASTS OF CHINA

Helice tientsinensis and H. latimera are among the most common crabs along the coast of China. They burrow in muddy substrates of upper littoral and supralittoral zones, especially in habitats of deduced salinity such as salt marshes and estuaries. The identification of species mostly relied on the size, shape and number of infraorbital crest. However, the key morphological differences are variable within species and greatly differ between sexes, and the females of both species could not be distinguished by the shape and number of infraorbital crest. Based on 33 proportional parameters of morphometric characters, three multivariation analysis methods were conducted to investigate the morphological variations among six populations (collected from Dandong and Panjin, Liaoning Province; Tanggu, Tianjin City; Rizhao and Weihai, Shandong Province; and Ningbo, Zhejiang Province) of Helice tientsinensis and four populations (collected from Ningbo, Zhejiang Province; Quanzhou, Fujian Province; Beihai, Guangxi Province and Haikou, Hainan Province) of H. latimera. The results of cluster analysis could not make the two species separated. While the Quanzhou population of H. latimera was clustered into one group, the other nine populations were clustered into another group. Normalized Euclidean Distances of morphology of the ten populations indicated close relationship each other. Discriminant analysis demonstrated that there were no significant differences (total discriminant accuracy was only 63.4%) among the ten populations. The identification accuracies of discriminant functions of Quanzhou population and Tanggu population were 88.9% and 75.0% respectively, while those of the other populations were all low. Principle component analysis revealed that ten populations were almost overlapped to each other in scatter diagram of the first and the second principal components, indicating only small morphological variations among these populations. The coefficients of difference (CD) of proportional parameters of morphometric characters among the ten populations were always lower than 1.28, a well-known critical value of subspecies. Males with osculant infraorbital crest were found in Ningbo where had a mixed population of H. tientsinensis and H. latimera, suggesting that H. tientsinensis and H. latimera might cross in their sympatric populations. The conspecific status of H. tientsinensis and H. latimera was further supported by published and our unpublished molecular analyses. However, there do exist difference in the infraorbital crest of male crabs. The infraorbital crest of populations north to Ningbo showed a pattern of H. tientsinensis, while those of southern populations showed a pattern of H. latimera. Therefore, we suggest to move both species down to subspecies level, i.e., Helice latimera latimera Parsis, 1918 and Helice latimera tientsinensis Rathbun, 1931.