#physalia

[snototter]

A Portuguese man o' war (Physalia physalis) in the waters of Dry Tortugas National Park, Florida, USA

by Helene Hoffman

[todropscience]

UNMASKING THE BLUEBOTTLE REVEALING FOUR DISTINCT SPECIES THROUGH GLOBAL CITIZEN SCIENCE

For over two centuries, the Portuguese man o’ war (Physalia spp) was considered a single, cosmopolitan species, drifting across the world’s oceans and stinging unsuspecting swimmers. But new genomic research has overturned this long-held view, revealing that Physalia is not one species, but at least four: P. physalis, P. megalista, P. utriculus, and a newly described species, P. minuta. Researchers sequenced the genomes of 151 specimens from around the globe and found strong reproductive isolation between genetic lineages, even when their distributions overlap. This evidence aligns with historical descriptions from the 18th and 19th centuries, which proposed several species that were later dismissed due to limited data.

Crucially, the study integrated over 4,000 photographs from iNaturalist, using citizen science to match distinct morphologies with genetic lineages. These images, contributed by amateur naturalists, swimmers, and lifeguards, allowed researchers to confirm physical differences that earlier taxonomists could not consistently observe due to preservation challenges. The result is a rare success story in which modern genomics, historical records, and participatory science come together to clarify the taxonomy of one of the ocean’s most recognisable creatures.

The discovery not only rewrites the story of Physalia but also challenges assumptions about biodiversity in the open ocean, reminding us that even the most visible marine life can hold hidden complexity, and that everyone, from sailors of the past to today’s citizen scientists, has a role to play in uncovering it.

Reference: Church et al., 2025. Population genomics of a sailing siphonophore reveals genetic structure in the open ocean. Current Biology.

[kororobus]

Sting! Physalia mermaid~

[zuhq]

Point Nemo Lineage

[faroukmarduk]

[colorsoutofearth]

Portuguese Man-of-War (Physalia physalis), Sargasso Sea, Bermuda

Photo by Solvin Zankl

[morphons]

Portuguese man o’ war (Physalia physalis). Long Rock Beach, Penzance, Cornwall.  October 2020.

[naturalsciencesbelgium]

This looks like a pretty jellyfish, with its tentacles. But in reality it is a Portuguese Man o’ War (Physalia physalis). Physalia is not a jellyfish, but a colony of four types of polyps (siphonophores). All these organisms together form a superorganism! The four different polyps all fulfill their own function: floating, stinging and catching prey, digestion, reproduction. Oh, #NatureIsTheGreatestShow ! The name comes from the animal’s resemblance to a warship of the same name, from the time of sailing ships. Physalia lives mainly in tropical and subtropical waters, but the gas-filled bladder, can carry it, driven by wind and tides, as far as Europe. Last weekend a walker on the beach at Raversijde in Ostend came upon a Portuguese Man o’ War, probably due to the recent stormy weather. The previous one seen on Belgian shores was more than a century ago. Even when stranded or even dead, this superorganism is highly venomous. Its tentacles of 10m on average (but which can reach over 30m!) cause, on contact, burns but could also lead to more serious reactions such as loss of consciousness, respiratory problems... So, don’t touch a stranded animal, despite its beautiful colours (generally purple, green and blue). [picture: Islands in the Sea, NOAA/OER]