A New Species of Zanclea innocens and New Record of Zanclea medusopolypata (Hydrozoa, Anthoathecata) from Japan

Cnidarian jellyfish (Medusozoa) comprise approximately 3800 known species which play important roles for marine ecosystem. This study aimed to understand the diversity of cnidarian jellyfish and symbiosis among marine organisms. The taxonomy of the family Zancleidae (Hydrozoa, Anthoathecata) has been problematic because of the limited differences in morphological characteristics between species. This family comprises approximately 40 species belonging to four genera: Apatizanclea, Halocoryne, Zanclea, and Zanclella. In this study, we describe a new species of hydromedusa belonging to the family Zancleidae found in Japanese waters. Zanclea innocens sp. nov. can be distinguished from other Zanclea species by the presence of nematocyst clusters on the exumbrella, slightly thickened apical projection, four narrow exumbrellar nematocyst pouches on ridges often reaching the umbrella apex, four marginal bulbs, and two tentacles. Additionally, Zanclea medusopolypata was recorded for the first time in Japanese waters. This paper provides taxonomic keys for the identification of species in the genus Zanclea.