Acartia huangi sp. nov., a new species of Acartia from Taiwan Strait

Acartiids are diminutive copepods geographically distributed across temperate and tropical zones, dominating zooplankton biomass in.estuarine and near coastal waters. They not only play an important role in the zooplanktonic community, but hold significant importance in aquaculture. With high nutritional value and adult sizes generally not exceeding 2 mm in length, Acartiids serve as excellent live prey for fishes, shrimps and crabs larvae during the artificial propagation of aquatic animals. The present study describes a new species of Acartia Dana, 1846, A. huangi Guo & Gong, sp. nov., which was collected from Taiwan Strait between 2004 and 2020. In order to accurately identify the new species, this study was conducted based on integrated morphological and molecular analyses. Morphologically, this new species should be assigned to subgenus Odontacartia Steuer, 1915, characterized by the existence of rostral filaments, posterior corners of last pedigerous somite drawn out into lateral spines, and posterodorsal margin of 2nd urosome in the male with pointed processes. A. huangi Guo & Gong, sp. nov. mostly resembles A. erythraea s. l.,. but differs in the following characteristics: ① 2nd segment of female antennule with 2 spines posteriorly, while that of A. erythraea s. l. with 4 spines; ② 3rd segment of female fifth thoracic leg (P5) with 2 columns of spinules on the inner side, while both sides of female P5 smooth in A. erythraea s. l.; ③ each inner side of posterior corners of last pedigerous somite with 2 spines dorsally in male, while that of A. erythraea s. l. with only 1 spine dorsally; ④ posterodorsal margin of 3rd urosomite with 4 to 9 spines in male, while that of A. erythraea s. l. with only 2 spines; ⑤ the inner margin of 4th segment of male left P5 with a bifurcate process, while that of A. erythraea s. l. with a finger-like process. The mitochondrial cytochrome oxidase Ⅰ (mtCOⅠ) gene sequences supported the results based on morphological data with distinct pairwise genetic distances 0.182 to 0.194 between this species and A. erythraea s. l.. The phylogenetic tree using unweighted pair group method with arithmetic means (UPGMA) based on mtCOⅠ gene sequences also clearly distinguished individuals of two species, demonstrating that the new species is distinct from A. erythraea s. l.. This new species was named in honor of Prof. Huang Jiaqi (1941—2022) of Xiamen University for his excellent contributions to marine planktology. Type specimens of A. huangi Guo & Gong, sp. nov. were deposited in Museum of Marine Science and Technology, Xiamen University. This study not only enriches the species diversity of Acartia in China, but provides basic data for database of diet organisms and marine biological survey.