Abstract: The female and male individuals of Ligia cinerascens with different body weight were collected for morphometric analysis. The present study aims to understand the difference of body size of female and male ones and morphological change with body growth. The results showed that the body weight, body length and body width between female and male is similar during the early stage of growth, but male significantly overwhelms female at the later stage. Body length-weight regression model reveals the positive correlation between body length and weight. Furthermore, the fact that the positive correlation is better in male than in female benefits the precise measurement of male weight by its body length. The second antennas of female and male are not different and its growth are in accord with the body length and width. The number of flagellar segments is 28 no matter with the gender and body weight. Moreover, the proportion of second antenna and its segments to body length is very stable. These parameters can be considered as important references for the taxonomy of Ligia cinerascens. At the early stage, the uropods of female and male are not different. The growth of male uropod is faster than that of female at the middle stage, however the difference of both is reduced again at the later stage. Briefly, the growth change of female uropod is more complicated than that of male. The proportion of exopod, endopod and protopd to body length is so stable to be considered as an important reference for the taxonomy of Ligia cinerascens. In comparison with the data from Japan, the present study indicates that the different populations independently dwelling in China and Japan exert the genetic differentiation due to long-time geographic isolation, where the difference is mainly reflected at the second antenna. 

Key words: Ligia cinerascens, Dalian, Heishijiao Gulf, morphological analysis