The infestation status of symbiotic crustaceans on the swimming crab Charybdis truncata (Fabricius, 1798) from Nha Trang Bay, Vietnam

Abstract

Symbioses are common relationships between organisms in marine ecosystems. Among the crabs belonging to Portunidae, an economically important family, Charybdis truncata is a wide distribution species. However, the studies on its symbiotic assemblages are still limited. A total of 408 C. truncata were collected in Nha Trang Bay - Khanh Hoa province from January to August 2022. The symbionts were classified based on morphological characteristics. Statistical analyses were applied to compare the infestation status of symbionts. Six symbiotic species including 4 epibiotic barnacles (Octolasmis angulata, O. alata, O. warwicki, Dianajonesia tridens), and 2 obligate unidentified parasites (Cancrion sp., and Sacculina sp.) were detected. Among these, O. alata and Cancrion sp. were recorded on C. truncata for the first time. The overall prevalence of symbionts on crab hosts was 13% and the number of infecting symbionts/host ranges from 1-4 species.  O. angulata was the dominant species with the prevalence (6.9%) higher than the others. The prevalence of O. angulata was significantly different between ovigerous and non-ovigerous female crabs, and host size groups. There were no significant differences in the mean intensity of symbionts by sexes, reproductive status of females, and size of crab hosts. The initial morphologic modifications caused by infected parasites (Sacculina sp. and Cancrion sp.) were recorded, and described. These findings provide information on the status of natural infection of symbiotic species on C. truncata, as a basis for the management of commercial species, as well as aquaculture development.

Keywords: Charybdis truncata, symbionts, epibionts, obligate parasites, Nha Trang Bay, Vietnam