Two new genera of the family Zosimeidae (Copepoda: Harpacticoida) from the northwestern Pacific

Abstract

Although the Zosimeidae appear to exhibit high species diversity in marine environments, their taxonomy in the Pacific Ocean is poorly understood. Only four species of the genus Zosime Boeck, 1873 are known from Korean waters to date. During oceanographic cruises exploring the species diversity of harpacticoids, two undescribed zosimeid copepods were sampled, from shallow Korean water and the deep northwestern Pacific, respectively. A detailed morphological examination has led us to create this proposal of two new genera, Zosimeidae n. gen. 1 for the Korean zosimeid copepod and Zosimeidae n. gen. 2 for the deep-sea zosimeid copepod. The former genus is well defined by a two-segmented exopod in the first thoracic leg. The latter genus shares this significant condition with Zosimeidae n. gen. 1, but can be discriminated from other genera by the plesiomorphic states of the antenna and maxilliped and the reduced segmentation and setal armature of the thoracic legs. A comparison of the fundamental structures of appendages suggests that Zosimeidae n. gen. 2 experienced a unique evolutionally history within the Zosimeidae. We provided herein the detailed illustrations of two new genera and a key to genera of the family.