NHK broadcast the findings of our laboratory. We are exceptionally proud of our team’s achievement and delighted by the public interest generated by our research.
The broadcast provided a concise overview of the discovery and the underlying shift in marine currents that led the specimens to be washed ashore in Sendai Bay.
As Professor Ames stated:
“The discovery of this new species was incredibly exciting and a fortunate find, but it also serves as an indicator that the species is migrating north due to climate change.”
Tohoku University just released a press release show casing the most recent lab discovery at Sendai Bay. The before-mentioned “Mikazuki no Eboshi”
The emergence of this species may be related to changes in the marine environment caused by climate change, such as the northward shift of the Kuroshio Current and rising sea temperatures. The northward movement of poisonous species not only changes the ecosystem, but also requires caution when swimming in the sea.
This is the first record of the Portuguese man-of-war genus in the Tohoku region. Furthermore, particle tracking simulations revealed that the northward shift of the Kuroshio Current and rising sea temperatures may be related to the emergence of this species. The observation of the Mikazuki no Eboshi provides important evidence that climate change is affecting the distribution of marine life.
Dr. Cheryl Ames is pioneering accessible and rapid methods for tracking marine biodiversity, with a special focus on box jellyfish and shifting octopus populations.
She uses Environmental DNA (eDNA), a technique that involves analyzing trace amounts of DNA left behind by species in the ocean water. By employing a field-ready eDNA pipeline that includes portable equipment like the Bento Lab, Dr. Ames and her students can conduct on-site PCR and quickly assess species presence, making data generation reliable even in remote areas.
This method allows researchers to generate data for critical issues, such as predicting the presence of highly venomous jellyfish for public safety, and providing sustainable fishing advice to local communities facing dramatic shifts in octopus populations following the 2011 tsunami.
Dr. Ames is committed to making advanced DNA analysis affordable and accessible, ensuring the next generation of scientists can apply these crucial techniques in any environment, regardless of laboratory resources.
This post is based on the article published by Bento Lab.
Discover the immediate dilemmas facing the Enoshima Aquarium—and what this means for their highly successful Portuguese Man-of-War exhibit.
Following the big splash made by the scientific discoveries originating from our lab, the established understanding of Physalia (the Portuguese Man-of-War) has been revolutionized. Research, which included the recent identification of Physalia mikazuki by our lab, now shows that what was once thought to be a single species first expanded to four and, with our lab’s subsequent discovery, grew to five distinct species in just over three months.
Opening what promises to be an amazing series in the Enoshima Aquarium Trainer’s Journal, Trainer Yamamoto presents a critical series of questions that highlight the practical impact of new taxonomy:
“Will we need to change the scientific names listed on our fish display boards and exhibits? Which species does the Japanese common name ‘Katsuo-no-Eboshi’ actually refer to? Since it is famous as a ‘highly venomous creature,’ are all five species equally dangerous?”
We are closely monitoring the developments at the Enoshima Aquarium and anxiously awaiting the answers to their questions.
It’s amazing to see the far-reaching impact of new and relevant scientific discoveries. You can find the full original post in the Enoshima Aquarium Trainer’s Journal here:
Changing Marine Ecosystems: Biogeography of Habitat Shifts and Adaptation to Oceanographic Variability
Date
Thursday, November 20, 2025 – 09:00 to Friday, November 21, 2025 – 18:00
This event will be the fifth joint workshop between Tohoku University and OIST since 2021. This time, WPI-AIMEC (Tohoku U & JAMSTEC) is co-organizing the event. It will include presentations that provide an overview of the current status and challenges of research on the marine environment and marine ecosystems, to promote the exchange of knowledge among researchers from Tohoku University, JAMSTEC, OIST, as well as University of the Ryukyus, and the University of Hawai’i. A majority of presentations will be given by early career researchers, with ample time for discussion to consider future collaborations and joint funding applications.
New, Venomous Portuguese Man-of-War Discovered in Japan’s North: Physalia mikazuki
This new species, named Physalia mikazuki (“crescent helmet man-o-war”) in honor of the samurai lord Date Masamune, marks the northernmost recorded presence of the Physalia genus to date, with specimens collected off the coast of northeastern Japan (Sendai Bay).
A student-led research team at Tohoku University (greatly formed by our lab) has formally identified a previously unknown species of the venomous siphonophore, Physalia —commonly known as the Portuguese man-of-war.
Key Scientific Findings:
New Species Identification: Through detailed morphological examination and genetic analysis, the team confirmed that P. mikazuki is genetically distinct from its tropical relatives, specifically Physalia utriculus, which was previously believed to be the only species of the genus inhabiting Japanese waters.
Climate-Driven Range Extension: The appearance of P. mikazuki in the colder waters of the Tohoku region suggests a significant shift in marine distribution. Ocean surface current simulations confirmed that the northward extension of the Kuroshio Current, combined with unusually high sea-surface temperatures, likely transported the colonies to Sendai Bay.
Ecological Significance: The discovery provides direct evidence that climate-related changes in ocean circulation are actively reshaping the distribution of marine species, highlighting the urgency of coastal observation.
The research not only adds a new species to the world’s taxonomic records but also underscores the immediate impact of climate change on ocean ecosystems, influencing where even dangerous marine life can drift and thrive.
In a rare marine encounter, researchers in Japan have uncovered a previously unidentified species of Portuguese man-of-war, Physalia mikazuki, off the coast of northeastern Japan. This marks the first time such a venomous jellyfish has been documented so far north in the country, with experts tying its arrival to warmer waters and changing currents.
A new species of Portuguese man o’ war has been discovered floating in the waters of northeast Japan. Spotted by a student-led research group, the discovery marks a species that has never been seen before in the area, raising questions about shifting distributions of marine creatures due to the effects of climate change.
The lab work is making a big impact in the media. We are proud to display the media coverage here and you can access the complete story on the IFLScience website.
Our recent research paper, detailing the discovery of a new venomous jellyfish species in Japan, has captured international media attention, with outlets highlighting the fascinating cultural connection of its name and its critical implications for marine science.
The discovery, published in Frontiers in Marine Science, confirms the existence of Physalia mikazuki sp. nov.—a new type of Portuguese Man-of-War found unexpectedly far north in Japan’s Tohoku region.
A Name Worthy of a Warrior
The media coverage, including articles from Tohoku University, Asia Research News, and ScienceDaily, emphasized the unique story behind the new species’ name. The jellyfish was named P. mikazuki (“crescent helmet man-o-war”) as an homage to the legendary samurai warrior and feudal lord of Sendai, Date Masamune, who was famous for the crescent moon (mikazuki) adorning his helmet.
This culturally significant name drew attention to a serious scientific finding: the species’ arrival in the temperate Tohoku region is a direct result of marine ecosystem change.
Climate Change Drives Species North
The research, led by a team including Cheryl Lewis Ames, Chanikarn Yongstar, Kei Chloe Tan, and Ayane Totsu, suggests that warming coastal waters and the northward shift of the Kuroshio Current are pushing tropical species into previously untouched temperate zones. The study used DNA analysis and particle simulation modeling (as highlighted by the coverage) to confirm the species is distinct and to track its probable drift path from warmer waters.
This finding serves as a powerful indicator of how climate change is rapidly altering the global distribution of marine organisms, necessitating increased monitoring to ensure coastal safety and ecological understanding.
A groundbreaking study co-authored by Cheryl Lewis Ames, Chanikarn Yongstar, Kei Chloe Tan, Ayane Totsu, and colleagues, has led to the identification of a new species of Portuguese Man-of-War (Physalia mikazuki sp. nov.) found in the waters of northeastern Japan (Tohoku).
The research, which also contou com Yoshiki Ochiai, Muhammad Izzat Nugraha, e Waka Sato-Okoshi, attributes the sudden presence of this new species in the temperate region to significant marine ecosystem changes. This discovery is vital for understanding how environmental shifts—such as changes in currents and climate—are forcing the global redistribution of marine organisms.
The findings emphasize the urgent need to monitor these shifts to protect marine biodiversity.
Authors: Chanikarn Yongstar, Yoshiki Ochiai, Muhammad Izzat Nugraha, Kei Chloe Tan, Ayane Totsu, Waka Sato-Okoshi, Cheryl Lewis Ames
