Zoological Studies

Vol. 62, 2023

(update: 2023.10.05)

Integrative Systematics and Biogeography of the Hydrozoans (Leptothecata: Eirenidae) Eirene menoni Kramp, 1953 and Eirene lacteoides Kubota and Horita, 1992 from Japan and China with Comments on Pacific Ocean Distributions

Gerald L. Crow1,*, Brenden S. Holland2, Gaku Yamamoto3, Shuhei Ikeda4, Aya Adachi3, and Kelley Niide5

1Ocean Research Explorations, P. O. Box 235926, Honolulu, Hawaii 96823. *Correspondence: E-mail gcrow@hawaii.edu (Crow)
2Department of Natural Sciences, College of Natural and Computer Sciences, Hawaii Pacific University, 45-045 Kamehameha Highway, Kaneohe, Hawaii 96744. E-mail: bholland@hpu.edu (Holland)
3Enoshima Aquarium, 2-19-1 Katase Kaigan, Fujisawa, Kanagawa Prefecture 251-0035, Japan. E-mail: g-yamamoto@enosui.com (Yamamoto); adati@enosui.com (Adachi)
4Tsuruoka City Kamo Aquarium, 656 Okubo Imaizumi, Tsuruoka, Yamagata Prefecture 997-1206, Japan. E-mail: s.ikeda@kamo-kurage.jp (Ikeda)
5Waikiki Aquarium, University of Hawaii at Manoa, 2777 Kalakaua Avenue, Honolulu, Hawaii 96815. E-mail: kelleyl@hawaii.edu (Niide)

(Received 4 November 2022 / Accepted 4 August 2023 / Published 5 October 2023)
Communicated by James D. Reimer

The hydrozoan family Eirenidae is known scientifically for its morphological plasticity and challenges in species identification. We used an integrative taxonomic approach based on morphological, molecular and life history evidence to systematically assess field-collected medusae of Eirene menoni Kramp 1953 and captive raised polyps of both E. menoni and E. lacteoides Kubota and Horita 1992. Following morphological review, we updated the genus description to include the presence of rudimentary bulbs (warts) on the ring canal in at least eight of the 24 valid Eirene species. We propose the potential for the mature E. menoni hydrotheca to develop into a gonotheca. However, this proposal will require additional study for verification. We provide validated distribution records from the Indo-Pacific Ocean for E. menoni, and updated collection records for E. lacteoides from the Yellow and East China Seas, and public aquaria-cultured specimens from Japan and Hawaii, using cytochrome c oxidase I (COI) sequences that we generated and compared with those from GenBank. The COI gene reliably separated four species, each forming a monophyletic clade with strong bootstrap support and low mean intraspecific molecular divergences (≤ 1%) within clades. However, some of the deeper nodes of the tree remained poorly resolved, and our analysis failed to demonstrate monophyly among eirenid genera Eirene and Tima. Our integrative taxonomic approach is essential in confirming species identity within the family Eirenidae and genus Eirene, and we have also identified a likely range expansion of E. lacteoides to Hawaii.

Key words: Hydrozoa, Leptomedusae, Plasticity, Campanulinida hydroid, COI mtDNA

Citation: Crow GL, Holland BS, Yamamoto G, Ikeda S, Adachi A, Niide K. 2023. Integrative systematics and biogeography of the hydrozoans (Leptothecata: Eirenidae) Eirene menoni Kramp, 1953 and Eirene lacteoides Kubota and Horita, 1992 from Japan and China with comments on Pacific Ocean distributions. Zool Stud 62:49. doi:10.6620/ZS.2023.62-49