Biology:Portuguese man o' war

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Short description: A siphonophore in the genus Physalia; also known as the Pacific man o' war

Portuguese man o' war
Portuguese Man-O-War (Physalia physalis).jpg
Scientific classification edit
Domain: Eukaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Order: Siphonophorae
Suborder: Cystonectae
Family: Physaliidae
Brandt, 1835[2]
Genus: Physalia
Lamarck, 1801[1]
P. physalis
Binomial name
Physalia physalis
Family-level synonym[3]
  • Physalidae Brandt, 1835 (original spelling)
Genus-level synonyms[4]
  • Arethusa Oken, 1815
  • Holothuria Linnaeus, 1758
  • Physalis Tilesius, 1810
  • Physsophora Modéer, 1789
Species-level synonyms[5]
  • Arethusa caravell Oken, 1815
  • Holothuria velificans Osbeck, 1765
  • Medusa utriculus Gmelin, 1788
  • Physalia australis Péron, 1807
  • Physalia gigantea Bory de St Vincent, 1894
  • Physalia glauca Tilesius, 1810
  • Physalia megalista Lesueur & Petit
  • Physalia pelagica Lamarck, 1801
  • Physalia pelasgica Bosc, 1802
  • Physalia utriculus Gmelin, 1788
  • Physalis afer Tilesius, 1810
  • Physalis arethusa Tilesius, 1810
  • Physalis cornuta Tilesius, 1810
  • Physalis elongata Lamarck, 1816
  • Physalis glauca Tilesius, 1810
  • Physalis lamartinieri Tilesius, 1810
  • Physalis megalista Lamarck, 1816
  • Physalis osbeckii Tilesius, 1810
  • Physalis pelagica Tilesius, 1810
  • Physalis pelagica Lamarck, 1816
  • Physalis tuberculosa Lamarck, 1816
  • Physsophora physalis Modéer, 1789

The Portuguese man o' war (Physalia physalis), also known as the man-of-war,[6] bluebottle, blue bottle jellyfish,[7] or floating terror is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war, which is found mainly in the Pacific Ocean.

The Portuguese man o' war is the only species in the genus Physalia, which in turn is the only genus in the family Physaliidae.[8] It has numerous venomous microscopic nematocysts which deliver a painful sting powerful enough to kill fish, and has been known to occasionally kill humans. Although it superficially resembles a jellyfish, the Portuguese man o' war is in fact a siphonophore. Like all siphonophores, it is a colonial organism, made up of many smaller units called zooids.[9] All zooids in a colony are genetically identical, but fulfill specialized functions such as feeding and reproduction, and together allow the colony to operate as a single individual.


The name man o' war comes from the man-of-war, an 18th-century sailing warship,[10] and the animal's resemblance to the Portuguese version (the caravel) at full sail.[11][5][6]


Portuguese man o' war are often found ashore in large groups. Photo from Faial, Azores

Found mostly in tropical and subtropical waters,[12][13] the Portuguese man o' war lives at the surface of the ocean. The gas-filled bladder, or pneumatophore, remains at the surface, while the remainder is submerged.[14] Portuguese men o' war have no means of propulsion, and move passively, driven by the winds, currents, and tides.

Strong winds may drive them into bays or onto beaches. Often, finding a single Portuguese man o' war is followed by finding many others in the vicinity.[15] Because they can sting while beached, the discovery of a man o' war washed up on a beach may lead to the closure of the beach.[16][17]

Anatomy and physiology

Illustration of Physalia physalis, 1807

Just like all siphonophores, the Portuguese man o' war is colonial: each man o' war is composed of many smaller units (zooids) that hang in clusters from under a large, gas-filled structure called the pneumatophore.[18] New zooids are added by budding as the colony grows. As many as seven different kinds of zooids have been described in the man o' war: three of the medusoid type (gonophores, nectophores, and vestigial nectophores) and four of the polypoid type (free gastrozooids, tentacle-bearing zooids, gonozooids and gonopalpons).[19] However, naming and categorization of zooids varies between authors, and much of the embryonic and evolutionary relationships of zooids remains unclear.[9]

The pneumatophore, or bladder, is the most conspicuous part of the man o' war. It is translucent and tinged blue, purple, pink, or mauve, and may be 9 to 30 centimetres (3.5 to 11.8 inches) long and rise as high as 15 cm (6 in) above the water. The pneumatophore functions as both a flotation device and a sail for the colony, allowing the colony to move with the prevailing wind.[9][18] The gas in the pneumatophore is part carbon monoxide (0.5–13%), which is actively produced by the animal, and part atmospheric gases (nitrogen, oxygen and noble gases) that diffuse in from the surrounding air.[20] In the event of a surface attack, the pneumatophore can be deflated, allowing the colony to temporarily submerge.[21]

The colony hunts and feeds through the cooperation of two types of zooid: gastrozooids and tentacle-bearing zooids known as dactylozooids[9] or tentacular palpons. The dactylozooids are equipped with tentacles, which are typically about 10 m (30 ft) in length but can reach over 30 m (100 ft).[15][22] Each tentacle bears tiny, coiled, thread-like structures called nematocysts. Nematocysts trigger and inject venom on contact, stinging, paralyzing, and killing adult or larval squids and fishes. Large groups of Portuguese man o' war, sometimes over 1,000 individuals, may deplete fisheries.[19][21] Contraction of tentacles drags the prey upward, into range of the gastrozooids, the digestive zooids. The gastrozooids surround and digest the food by secreting enzymes.

The main reproductive zooids, the gonophores, are situated on branching structures called gonodendra. Gonophores produce sperm or eggs (see life cycle). Besides gonophores, each gonodendron also contains several other types of specialized zooids: gonozooids (which are accessory gastrozooids), nectophores (which have been speculated to allow detached gonodendra to swim), and vestigial nectophores (also called jelly polyps; the function of these is unclear).[9]


The man o' war is described as a colonial organism because the individual zooids in a colony are evolutionarily derived from either polyps or medusae,[23] i.e. the two basic body plans of cnidarians.[24] Both of these body plans comprise entire individuals in non-colonial cnidarians (for example, a jellyfish is a medusa; a sea anemone is a polyp). All zooids in a man o' war develop from the same single fertilized egg and are therefore genetically identical; they remain physiologically connected throughout life, and essentially function as organs in a shared body. Hence, a Portuguese man o' war constitutes a single individual from an ecological perspective, but is made up of many individuals from an embryological perspective.[23]

Left- or right-handedness

A Portuguese man o' war is somewhat asymmetrically shaped: the zooids of the colony hang down not quite from the midline of the pneumatophore, but offset to either the right or left side of the midline. When combined with the trailing action of the tentacles (which function as a sea anchor), this left- or right-handedness makes the colony sail sideways relative to the wind, by about 45° in either direction.[25][26] Colony handedness has therefore been theorized to affect man o' war migration, with left-handed or right-handed colonies potentially being more likely to drift down particular respective sea routes.[25] While previously believed to develop as a result of what winds a colony experienced, handedness in fact emerges early in the colony's life, while it is still living below the surface of the sea.[9]

Life cycle

Man o' war individuals are dioecious, meaning each colony is either male or female.[18][9] Gonophores producing either sperm or eggs (depending on the sex of the colony) sit on a tree-like structure called a gonodendron, which is believed to drop off from the colony during reproduction.[9] Mating takes place primarily in the autumn, when eggs and sperm are shed from gonophores into the water.[18] As neither fertilization nor early development have been directly observed in the wild, it is not yet known at what depth they occur.[9]

A fertilized man o' war egg develops into a larva that buds off new zooids as it grows, gradually forming a new colony. This development initially occurs under the water, and has been reconstructed by comparing different stages of larvae collected at sea.[9] The first two structures to emerge are the pneumatophore (sail) and a single, early feeding zooid called a protozooid; later, gastrozooids and tentacle-bearing zooids are added. Eventually, the growing pneumatophore becomes buoyant enough to carry the immature colony on the surface of the water.[9]


Man o' war warning sign at Hawaii

This species is responsible for up to 10,000 human stings in Australia each summer, particularly on the east coast, with some others occurring off the coast of South Australia and Western Australia.[27]

The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o' war can paralyze small fish and other prey.[28] Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live organism in the water, and may remain potent for hours or even days after the death of the organism or the detachment of the tentacle.[29]

Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that normally last two or three days after the initial sting, though the pain should subside after about 1 to 3 hours (depending on the biology of the person stung). However, the venom can travel to the lymph nodes and may cause symptoms that mimic an allergic reaction, including swelling of the larynx, airway blockage, cardiac distress, and an inability to breathe. Other symptoms can include fever and shock, and in some extreme cases, even death,[30] although this is extremely rare. Medical attention for those exposed to large numbers of tentacles may become necessary to relieve pain or open airways if the pain becomes excruciating or lasts for more than three hours, or if breathing becomes difficult. Instances where the stings completely surround the trunk of a young child are among those that have the potential to be fatal.[31]

Treatment of stings

Stings from a Portuguese man o' war are often extremely painful. They result in severe dermatitis characterized by long, thin, open wounds that resemble those caused by a whip.[32] These are not caused by any impact or cutting action, but by irritating urticariogenic substances in the tentacles.[33][34] Flushing the affected area with sea water helps remove any adherent tentacles in the wound area.[31][35][36][37]

Acetic acid (vinegar) or a solution of ammonia and water is popularly believed to deactivate the remaining nematocysts and usually provides some pain relief,[31] though some isolated studies suggest that in some individuals vinegar dousing may increase toxin delivery and worsen symptoms.[35][38] Vinegar has also been claimed to provoke hemorrhaging when used on the less severe stings of cnidocytes of smaller species.[39] The current recommended treatment from studies in Australia is to avoid the use of vinegar, as local studies have shown this to exacerbate the symptoms.

The ammonia soak is then often followed by the application of shaving cream to the wound for 30 seconds, followed by shaving the area with a razor and rinsing the razor thoroughly between each stroke. This removes any remaining unfired nematocysts. Heat in the form of hot saltwater or hot packs may be applied: heat speeds the breakdown of the toxins already in the skin. Hydrocortisone cream may also be used.[31]

A 2017 study stated that a wash of undiluted vinegar or Sting No More Spray, a proprietary "combined stinging capsule and venom-inhibiting product" were the most effective topical rinse solutions.[40] The vinegar (or spray) rinse should be followed by immersion in 45°C (113°F) water or application of a hot pack for 45 minutes.[41]

Predators and prey

The Portuguese man o' war is a carnivore.[15] Using its venomous tentacles, a man o' war traps and paralyzes its prey while "reeling" it inwards to the digestive polyps. It typically feeds on small marine organisms, such as fish and plankton and sometimes shrimp.

The organism has few predators of its own; one example is the loggerhead turtle, which feeds on the Portuguese man o' war as a common part of its diet.[42] The turtle's skin, including that of its tongue and throat, is too thick for the stings to penetrate. Also, the blue sea slug Glaucus atlanticus specializes in feeding on the Portuguese man o' war,[43] as does the violet snail Janthina janthina.[44] The ocean sunfish's diet, once thought to consist mainly of jellyfish, has been found to include many species, the Portuguese man o' war being one such example.[45][46]

The blanket octopus is immune to the venom of the Portuguese man o' war; young individuals have been observed to carry broken man o' war tentacles,[47] which males and immature females rip off and use for offensive and defensive purposes.[48]

Commensalism and symbiosis

A small fish, Nomeus gronovii (the man-of-war fish or shepherd fish), is partially immune to the venom from the stinging cells and can live among the tentacles. It seems to avoid the larger, stinging tentacles but feeds on the smaller tentacles beneath the gas bladder. The Portuguese man o' war is often found with a variety of other marine fish, including yellow jack.

All these fish benefit from the shelter from predators provided by the stinging tentacles, and for the Portuguese man o' war, the presence of these species may attract other fish to eat.[49]


See also


  1. Lamarck, J. B. (1801). Système des animaux sans vertèbres, ou tableau général des classes, des ordres et des genres de ces animaux; Présentant leurs caractères essentiels et leur distribution, d'apres la considération de leurs rapports naturels et de leur organisation, et suivant l'arrangement établi dans les galeries du Muséum d'Histoire Naturelle, parmi leurs dépouilles conservées; Précédé du discours d'ouverture du Cours de Zoologie, donné dans le Muséum National d'Histoire Naturelle l'an 8 de la République. Published by the author and Deterville, Paris: viii + 432 pp., available online at page(s): 355
  2. Brandt, J. F. 1834-1835. Prodromus descriptionis animalium ab H. Mertensio in orbis terrarum circumnavigatione observatorum. Fascic. I., Polypos, Acalephas Discophoras et Siphonophoras, nec non Echinodermata continens / auctore, Johanne Friderico Brandt. - Recueil Actes des séances publiques de l'Acadadémie impériale des Science de St. Pétersbourg 1834: 201-275., available online at page(s): 236
  3. Schuchert, P. (2019). World Hydrozoa Database. Physaliidae Brandt, 1835. Accessed through: World Register of Marine Species at: on 2019-03-11
  4. Schuchert, P. (2019). World Hydrozoa Database. Physalia Lamarck, 1801. Accessed through: World Register of Marine Species at: on 2019-03-11
  5. 5.0 5.1 Schuchert, P. (2019). World Hydrozoa Database. Physalia physalis (Linnaeus, 1758). Accessed through: World Register of Marine Species at: on 2019-03-11
  6. 6.0 6.1 Portuguese man-of-war (3rd ed.), Oxford University Press, September 2005,  (Subscription or UK public library membership required.)
  7. "Blue bottle jellyfish back on Mumbai's Juhu beach, experts warn visitors to avoid contact" (in en). 2021-08-03. 
  8. [1]
  9. 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 Munro, Catriona; Vue, Zer; Behringer, Richard R.; Dunn, Casey W. (2019). "Morphology and development of the Portuguese man of war, Physalia physalis". Scientific Reports 9 (1): 15522. doi:10.1038/s41598-019-51842-1. PMID 31664071. Bibcode2019NatSR...915522M. 
  10. Greene, Thomas F.. Marine Science Textbook. 
  11. Millward, David (8 September 2012). "Surge in number of men o'war being washed up on beaches". The Daily Telegraph. 
  12. "What is a Portuguese Man o' War?". NOAA. 
  13. "Portuguese Man-O'-War". 24 April 2014. 
  14. Clark, F. E.; C. E. Lane (1961). "Composition of float gases of Physalia physalis". Proceedings of the Society for Experimental Biology and Medicine 107 (3): 673–674. doi:10.3181/00379727-107-26724. PMID 13693830. 
  15. 15.0 15.1 15.2 "Portuguese Man-of-War". National Geographic Society. 
  16. "Dangerous jellyfish wash up". BBC News. 2008-08-18. /
  17. "Man-of-war spotted along coast in Cornwall and Wales". BBC. 12 September 2017. 
  18. 18.0 18.1 18.2 18.3 "Physalia physalis, Portuguese man-of-war". Museum of Zoology, University of Michigan. 
  19. 19.0 19.1 Bardi, Juliana; Marques, Antonio C (2007). "Taxonomic redescription of the Portuguese man-of-war, Physalia physalis (Cnidaria, Hydrozoa, Siphonophorae, Cystonectae) from Brazil". Iheringia, Sér. Zool. (Brazil: Fundação Zoobotânica do Rio Grande do Sul) 97 (4): 425–433. doi:10.1590/S0073-47212007000400011. ISSN 1678-4766. 
  20. Wittenberg, Jonathan B. (1960-01-12). "The Source of Carbon Monoxide in the Float of the Portuguese Man-of-War, Physalia physalis L". Journal of Experimental Biology 37 (4): 698–705. doi:10.1242/jeb.37.4.698. ISSN 0022-0949. Retrieved 2013-02-12. 
  21. 21.0 21.1 "Portuguese Man-of-War". National Geographic Animals. National Geographic. 11 November 2010. 
  22. NOAA (27 July 2015). "What is a Portuguese Man o' War?". National Ocean Service. "Updated 10 October 2017" 
  23. 23.0 23.1 Dunn, Casey. "Colonial organization". 
  24. "Polyp and medusa body shapes". Manatū Taonga/Ministry for Culture and Heritage, Wellington, New Zealand. 
  25. 25.0 25.1 Woodcock, A. H. (1956). "Dimorphism in the Portuguese man-of-war". Nature 178 (4527): 253–255. doi:10.1038/178253a0. Bibcode1956Natur.178..253W. 
  26. Iosilevskii, G.; Weihs, D. (2009). "Hydrodynamics of sailing of the Portuguese man-of-war Physalia physalis". Journal of the Royal Society Interface 6 (36): 613–626. doi:10.1098/rsif.2008.0457. PMID 19091687. 
  27. Fenner, Peter J.; Williamson, John A. (December 1996). "Worldwide deaths and severe envenomation from jellyfish stings". Medical Journal of Australia 165 (11–12): 658–661. doi:10.5694/j.1326-5377.1996.tb138679.x. ISSN 0025-729X. PMID 8985452. "In Australia, particularly on the east coast, up to 10 000 stings occur each summer from the bluebottle (Physalia spp.) alone, with others also from the "hair jellyfish" (Cyanea) and "blubber" (Catostylus). Common stingers in South Australia and Western Australia, include bluebottle, as well the four-tentacled cubozoa or box jellyfish, the "jimble" (Carybdea rastoni)". 
  28. Yanagihara, Angel A.; Kuroiwa, Janelle M.Y.; Oliver, Louise M.; Kunkel, Dennis D. (December 2002). "The ultrastructure of nematocysts from the fishing tentacle of the Hawaiian bluebottle, Physalia utriculus (Cnidaria, Hydrozoa, Siphonophora)". Hydrobiologia 489 (1–3): 139–150. doi:10.1023/A:1023272519668. 
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  30. Stein, Mark R.; Marraccini, John V.; Rothschild, Neal E.; Burnett, Joseph W. (March 1989). "Fatal Portuguese man-o'-war (Physalia physalis) envenomation". Ann Emerg Med 18 (3): 312–315. doi:10.1016/S0196-0644(89)80421-4. PMID 2564268. 
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  32. "Image Collection: Bites and Infestations: 26. Picture of Portuguese Man of War Sting" (in en). MedicineNet Inc. "The sting of the Portuguese man-of-war. One of the most painful effects on skin is the consequence of attack by oceanic hydrozoans known as Portuguese men-of-war, which are amazing for their size, brilliant color, and power to induce whealing. They have a small float that buoys them up and from which hang long tentacles. The wrap of these tentacles results in linear stripes, which look like whiplashes, caused not by the force of their sting but from deposition of proteolytic venom toxins, urticariogenic and irritant substances." 
  33. James, William D.; Berger, Timothy G.; Elston, Dirk M.; Odom, Richard B. (2006). Andrews' Diseases of the Skin: Clinical Dermatology. Saunders Elsevier. p. 429. ISBN 978-0-7216-2921-6. 
  34. Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 978-1-4160-2999-1. 
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  36. Yoshimoto, C.M.; Yanagihara, A.A. (May–June 2002). "Cnidarian (coelenterate) envenomations in Hawai'i improve following heat application". Transactions of the Royal Society of Tropical Medicine and Hygiene 96 (3): 300–303. doi:10.1016/s0035-9203(02)90105-7. PMID 12174784. Retrieved 2019-04-03. 
  37. Loten, Conrad; Stokes, Barrie; Worsley, David; Seymour, Jamie E.; Jiang, Simon; Isbister, Geoffrey K. (3 April 2006). "A randomised controlled trial of hot water (45 °C) immersion versus ice packs for pain relief in bluebottle stings". Medical Journal of Australia 184 (7): 329–333. doi:10.5694/j.1326-5377.2006.tb00265.x. PMID 16584366. 
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  39. Exton, D.R. (1988). "Treatment of Physalia physalis envenomation". Medical Journal of Australia 149 (1): 54. doi:10.5694/j.1326-5377.1988.tb120494.x. PMID 2898725. 
  40. Wilcox, Christie L.; Headlam, Jasmine L.; Doyle, Thomas K.; Yanagihara, Angel A. (May 22, 2017). "Assessing the Efficacy of First-Aid Measures in Physalia sp. Envenomation, Using Solution- and Blood Agarose-Based Models". Toxins 9 (5): 149. doi:10.3390/toxins9050149. PMID 28445412. 
  41. "SOEST scientists scrutinize first aid for man o' war stings". 
  42. Brodie (1989). Venomous Animals. Western Publishing Company. 
  43. Scocchi, Carla; Wood, James B.. "Glaucus atlanticus, Blue Ocean Slug". 
  44. Morrison, Sue; Storrie, Ann (1999). Wonders of Western Waters: The Marine Life of South-Western Australia. CALM. p. 68. ISBN 978-0-7309-6894-8. 
  45. Sousa, Lara L.; Xavier, Raquel; Costa, Vânia; Humphries, Nicolas E.; Trueman, Clive; Rosa, Rui; Sims, David W.; Queiroz, Nuno (4 July 2016). "DNA barcoding identifies a cosmopolitan diet in the ocean sunfish". Scientific Reports 6 (1): 28762. doi:10.1038/srep28762. PMID 27373803. Bibcode2016NatSR...628762S. 
  46. "Portuguese Man o' War", (Oceana),, retrieved 2017-04-02 
  47. "Tremoctopus". 
  48. Jones, E.C. (1963). "Tremoctopus violaceus uses Physalia tentacles as weapons". Science 139 (3556): 764–766. doi:10.1126/science.139.3556.764. PMID 17829125. Bibcode1963Sci...139..764J. 
  49. Piper, Ross (2007). "Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals". Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Greenwood Press. 
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Further reading

External links

Wikidata ☰ Q202526 entry