Discoveries from ornamental jellyfish in aquaria—description of Malagazzia michelin sp. nov. (Cnidaria, Hydrozoa, Leptothecata), second species of the genus from Japan

Malagazzia michelin sp. nov. is described as the ninth species in this genus. Medusae were collected in shallow waters of western Japan and observed in several aquaria, and cultures were maintained at the Tsuruoka City Kamo Aquarium and Saikai National Park Kuju-kushima Aquarium. Adult medusae were identified as belonging to the genus Malagazzia owing to the presence of excretory papillae on the tentacular bulbs and rudimentary bulbs, four gonads surrounding radial canals, and manubrium with four lips. The obtained polyps also exhibited the typical characters of this genus. However, these medusae can be distinguished from those of other species of Malagazzia by noticeable brown spot-like structures on the gonads and manubrium; combinations of several characters also suggest that the medusae represent an undescribed species. Malagazzia michelin sp. nov. is also demonstrated to be a Malagazzia species by a phylogenetic analysis using DNA sequences. Thus, we determine these individuals as the second and a new species from Japanese waters. We also discuss the challenge of common names used for medusae in aquaria in Japan.