ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Marine Molecular Biology and Ecology
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1653958
Physalia mikazuki sp. nov. (Phylum Cnidaria; Class Hydrozoa) Blown into Japan's Northeast (Tohoku) at the Whim of Marine Ecosystem Change
Provisionally accepted
Cheryl L Ames*
Chanikarn Yongstar*
Yoshiki Ochiai
Muhammad Izzat Nugraha
Kei Chloe Tan
Ayane Totsu
Waka Sato-Okoshi- Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
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The discovery of Physalia mikazuki sp. nov. in the temperate waters of Gamo Beach, Sendai Bay (Miyagi Prefecture) in the Tohoku (northeast) region of Japan, represents a significant addition to the taxonomic and ecological understanding of this genus. Morphological analysis reveals key diagnostic traits, distinguishing it from all known Physalia species. Phylogenetic analyses of the 16S rRNA gene and COI (cytochrome c oxidase subunit 1) regions further confirm its classification as a distinct species, forming a well-supported monophyletic clade separate from other Physalia species. Oceanographic data and Lagrangian particle trajectory simulation suggest that P. mikazuki may have dispersed northward via the recent 100 km northward extension of the Kuroshio Current (KE) in tandem with record-breaking sea surface temperature (SST) changes of more than 2 °C in the Tohoku region between 2022 and 2024. Long-term monitoring confirmed no previous reports of Physalia at the type locality of Gamo Beach, Sendai City (Tohoku) prior to 2023, suggesting a likely recent introduction. Molecular barcode sequences matching samples from both Pakistan and Mexico indicate a broad Indo-Pacific connectivity for the new species. The occurrence of P. mikazuki sp. nov. in the Tohoku region poses potential ecological and public health concerns, particularly due to its predation on fish larvae and risk of envenomation during beach recreation. This study underscores the importance of integrative experimental design combining taxonomy, molecular data, and oceanographic modeling to understand species range shifts and cryptic diversity in a changing ocean.
Keywords: Portuguese man-of-war, new species, Ecosystem change, Kuroshio Extension (KE), Distribution range
Received: 25 Jun 2025; Accepted: 06 Oct 2025.
Copyright: © 2025 Ames, Yongstar, Ochiai, Nugraha, Tan, Totsu and Sato-Okoshi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Cheryl L Ames, ames.cheryl.lynn.a1@tohoku.ac.jp
Chanikarn Yongstar, yongstar.chanikarn.s3@dc.tohoku.ac.jp
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