A new species of Pseudodiaptomus (Copepoda, Calanoida, Pseudodiaptomidae) from the coastal waters of northern Taiwan with notes on co-occurring and previously recorded species

Abstract We investigated the species diversity of the demersal copepod genus Pseudodiaptomus in the coastal waters of northern Taiwan, and recorded four species new to Taiwanese waters: P. echinatus n. sp., P. ishigakiensis Nishida, 1985, P. philippinensis Walter, 1986, and P. zhengi Wang & Guo, 2019. Pseudodiaptomus echinatus n. sp. is distinguished from the allied species P. serricaudatus (Scott T., 1894) by the female genital double-somite, which is laterally swollen and of subequal length and width, and the male fifth leg, the right endopod of which is oval with a row of spinules increasing in size toward the tip, and the first exopod segment of which has a distomedial digitiform process with rounded tip. In addition, out of the 11 nominal species previously recorded from Taiwanese waters, we found only three species ( P. annandalei Sewell, 1919, P. bispinosus Walter, 1984, P. trihamatus Wright, 1937). We were unable to confirm the presence of P. forbesi (Poppe & Richard, 1890), P. incisus Shen & Lee, 1963, P. inopinus Burckhardt, 1913, P. marinus Sato, 1913, P. pacificus Walter, 1986, P. penicillus Li & Huang, 1984, P. poplesia (Shen, 1955), and P. serricaudatus (T. Scott, 1894) by a critical review of available literature based on morphology, locality, habitat, etc. In this regard, it is necessary for a future study to try to verify the presence of these eight species in Taiwanese waters.