2022 年 17 巻 2 号 p. 221-230
The Paracalanus parvus (Claus, 1863) species complex is a common marine calanoid copepod found in the world’s oceans. Recent genetic analyses of its specimens from the world oceans revealed that the complex in the western North Pacific consists of three species, i.e., P. indicus Wolfenden, 1905, P. tropicus Andronov, 1977 and an undescribed species. We assign the last one to be Paracalanus orientalis n. sp. by comparing it with previous morphological descriptions of related species. Both sexes of the new species are fully described based on genetically identified specimens from the surface layer of the south of Japan. The new species can be reliably distinguished from P. indicus and P. tropicus by the hunchback shape of the female if it is clearly present. Among the three species, the high length:width ratio of the third exopod segment of leg 4 is also characteristic of the new species, which would be identifiable, in most cases, by having a ratio of 5.4 or more.
