Physalia

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Physalia
Physalia physalis.jpg
Physalia physalis , the Atlantic Portuguese man o' war
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Order: Siphonophorae
Family: Physaliidae
Brandt, 1835 [1] : 236–238 
Genus: Physalia
Lamarck, 1801 [2]
Type species
Physalia physalis
(Linnaeus, 1758)
Species
Synonyms
  • ArethusaOken, 1815
  • HolothuriaLinnaeus, 1758
  • PhysalisTilesius, 1810

Physalia is a genus of hydrozoan cnidarians within the monotypic family Physaliidae, commonly known as man o' wars or bluebottles. They are siphonophores, colonial organisms composed of specialized individual zooids that function together as a single unit. Unlike most siphonophores, which are planktonic, Physalia species are neustonic, living at the ocean-air interface.

Contents

Taxonomy and Systematics

The genus Physalia was established by Jean-Baptiste Lamarck in 1801. [3] The type species, the Atlantic Portuguese man o' war, was first described by Carl Linnaeus in 1758 as Holothuria physalis. [4]

For much of the 20th and early 21st centuries, the genus was often considered monotypic, containing only P. physalis, with other observed forms considered regional variants or growth stages. [5] However, morphological studies noted significant variation, and genetic analyses have since provided strong evidence for multiple, reproductively isolated species.

A pivotal 2025 population genomics study of specimens collected globally identified five distinct genetic lineages, supporting the recognition of at least four species. [6] This study integrated whole-genome sequencing with morphological analysis of thousands of citizen-science images from iNaturalist, linking genetic clusters to recognizable morphologies. It confirmed the validity of historically proposed species like P. utriculus and P. megalista , and described the new species P. minuta . [6]

Also in 2025, Physalia mikazuki was described from Japan based on distinct morphology and mitochondrial DNA sequences. [7]

Physalia is the sole genus in the family Physaliidae, within the siphonophore suborder Cystonectae . Cystonectae represents the earliest-diverging lineage of siphonophores. [8]

Species

The genus currently contains five recognized species:

Common nameScientific nameDescription / Distinguishing FeaturesDistribution
Portuguese Man o' War Physalia physalis (Linnaeus, 1758)Largest species; long, multiple tentacle clusters; tall sail crest.Primarily Atlantic Ocean
Indo-Pacific Man-o'-War
Bluebottle		 Physalia utriculus (La Martinière, 1787)Smaller float; often a single long fishing tentacle; shorter sail. Indo-Pacific Ocean.
Southern Man-o'-War Physalia megalista (Gould, 1852)Long, slender pneumatophore. Southern Hemisphere oceans.
Little Bluebottle Physalia minuta Church & Dunn, 2025Small, green-tinted float; short sail; short tentacles.Southwest Pacific.
Japanese Man-o'-War Physalia mikazuki Yongstar, Ochiai & Ames, 2025Crescent-moon shaped float (diagnostic).Northwestern Pacific (Japan).

References

  1. ↑ Brandt, Johann Friedrich (1834–1835). "Prodromus descriptionis animalium ab H. Mertensio in orbis terrarum circumnavigatione observatorum. Fascic. I., Polypos, Acalephas Discophoras et Siphonophoras, nec non Echinodermata continens". Recueil Actes des séances publiques de l'Acadadémie impériale des Science de St. Pétersbourg 1834: 201–275. Archived from the original on 2023-06-07. Retrieved 2023-06-07– via Biodiversity Heritage Library.
  2. ↑ Lamarck, J. B. (1801). Système des animaux sans vertèbres. Paris, France: by the author and Deterville. pp. 355–356. Archived from the original on 2023-06-07. Retrieved 2023-06-07– via Biodiversity Heritage Library.
  3. ↑ Lamarck, J.B. (1801). Système des animaux sans vertèbres. Paris: Deterville. p. 365.
  4. ↑ Linnaeus, C. (1758). Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Holmiae: Laurentii Salvii. p. 658.
  5. ↑ Bardi, Juliana; Marques, Antonio C. (2007). "Taxonomic redescription of the Portuguese man-of-war, Physalia physalis (Cnidaria, Hydrozoa, Siphonophorae, Cystonectae) from Brazil". Iheringia, Série Zoologia. 97 (4): 425–433. doi: 10.1590/S0073-47212007000400011 .
  6. 1 2 Church, Samuel H.; et al. (2025). "Population genomics of a sailing siphonophore reveals genetic structure in the open ocean". Current Biology. 35 (15): 3556–3569.e6. Bibcode:2025CBio...35.3556C. doi:10.1016/j.cub.2025.05.066. PMID   40541187.
  7. ↑ Yongstar, Chanikarn; et al. (2025). "Physalia mikazuki sp. nov. (Phylum Cnidaria; class Hydrozoa) blown into Japan's northeast (Tohoku) at the whim of marine ecosystem change". Frontiers in Marine Science. 12: 1653958. Bibcode:2025FrMaS..1253958Y. doi: 10.3389/fmars.2025.1653958 .{{cite journal}}: CS1 maint: article number as page number (link)
  8. ↑ Munro, Catriona; et al. (2018). "Improved phylogenetic resolution within Siphonophora (Cnidaria) with implications for trait evolution". Molecular Phylogenetics and Evolution. 127: 823–833. Bibcode:2018MolPE.127..823M. doi:10.1016/j.ympev.2018.06.030. PMC   6064665 . PMID   29940256.
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