Species diversity and molecular taxonomy of symbiotic crustaceans on Portunus pelagicus (Linnaeus, 1758) in Vietnam, with remarks on host records and morphological variation

Abstract The blue swimming crab (Portunus pelagicus (Linnaeus, 1758)) is an economically and ecologically important species in Vietnam, and a potential subject for aquaculture as well. More than 400 individual crabs were collected along the Vietnamese coastline and examined for ectosymbiotic crustaceans. Two molecular markers (28S rRNA and COI mtDNA) were applied for species delineation. Seven species were reported and described, of which six are cirripede barnacles (Thecostraca, Thoracia); and one parasitic copepod Choniosphaera indica Gnanamuthu, 1954 (Copepoda, Podoplea). Four species (Chelonibia testudinaria (Linnaeus, 1758), Semibalanus sp., Octolasmis neptuni (MacDonald, 1869), and Dianajonesia tridens (Aurivillius, 1894)) were the first records for both host and location. The symbiotic crustaceans occupy specific niches on the crab body, and vary in their infestation status. Molecular taxonomy of symbiotic crustaceans was classified and confirmed based on sequence similarity and phylogenetic analyses.