First record of the stalked jellyfish Haliclystus tenuis Kishinouye, 1910 (Cnidaria: Staurozoa) in Atlantic waters

Abstract

Combined morphological and molecular genetic analyses confirmed the occurrence of the stalked jellyfish Haliclystus tenuis Kishinouye, 1910 on the coast of the island Helgoland (North Sea, German Bight). The species was previously reported in Japan and China only, and it was assumed that its geographical range is limited to the northwest Pacific. Possibly, the species was overlooked in Atlantic waters because of its morphological similarity with the Atlantic species Haliclystus octoradiatus Clark, 1863. However, the low intra-specific variation in mitochondrial gene cytochrome c oxidase subunit I (COI) does not indicate a geographic separation of Atlantic and Pacific specimens and may indicate a non-native introduction.