Acartia huangi sp. nov., a new species of Acartia from the 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 also 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 fish, shrimp, and crab 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 the 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 the male's 2nd urosome has a posterodorsal margin with pointed processes. A. huangi Guo & Gong, sp. nov. mostly resembles A. erythraea s. l., but differs in the following characteristics: ① 2^nd segment of female antennule with 2 spines posteriorly, while that of A. erythraea s. l. with 4 spines; ② 3^rd 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 3^rd urosomite with 4 to 9 spines in male, while that of A. erythraea s. l. with only 2 spines; ⑤ the inner margin of 4^th 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 showing pairwise genetic distances of 0.182-0.194 with this species and A. erythraea s. l.. The phylogenetic tree using unweighted pair group method with arithmetic means (UPGMA) based on mtCOⅠgene sequences also clearly distinguished individuals of two species, and clearly distinguished the new species 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.