Characteristics of papillae in wild, cultivated and hybrid sea cucumbers (Apostichopus japonicus)

We investigated the characteristics of papillae of living, boiled and dried specimens of three wild populations, cultivated and hybrid Apostichopus japonicus in the laboratory. Visual observation showed that the appearance of the papillae was obviously different among the populations. For the first time, we established a standard criterion for estimating papilla number (PL/L ≥ 0.05, PL: the length of the papilla, L: body length) in living, boiled and dried A. japonicus . According to the criterion, we estimated the papilla number in living, boiled and dried specimens of wild, cultured and hybrid A. japonicus . Results show that the number of both dorsal and ventral papillae was significantly different among the groups. The largest total number of papillae was found in the Russian population (66.25 ± 8.11), which was significantly larger than those in the other groups (P<0.01). It was followed by those in the Japanese population and two hybrid groups (53.64 ± 7.88 for JJ, 54.65 ± 4.74 for CR and 46.29 ± 6.91 for CK). The differences between the number of dorsal and ventral papilla in Russian, Japanese and Chinese♂×Russian♀ hybrid populations were significantly larger than those in the other groups. This study increases our understanding of papilla traits in different populations of A. japonicus and has a direct application potential for selective breeding and its aquaculture. Key words: Apostichopus japonicus, papilla, criterion, hybrid.