Physalia physalis   (Linnaeus,  1758) (Hydrozoan)
Organism information awaits expert curation
Class: Hydrozoa

Image copyrights: Michigan Science Art

Physalia physalis is a floating hydrozoan. It is actually a colony consisting of four types of polyps: a pneumatophore, or float; dactylozooids, or tentacles; gastrozooids, or feeding zooids; and gonozooids which produce gametes for reproduction. Cnidocytes (stinging cells) are located in the tentacles. Their action is based on their individual osmotic and hydrostatic pressure. Sensory cells are numerous and are located in the epidermis of the tentacles and the region around the mouths. Generally, the sensory cells are receptors for touch and temperature. The stinging cells, or cnidocytes, are the characteristic food-getting mechanisms. It has two sizes of cnidocytes, some small and others are large. These cells retain their potency long after an individual has been washed up along the shore.
Locomotion is generally passive, driven by wind and current. The colony cannot swim, but floats by the aid of its pneumatophore, or float. The float is a long, gas-filled bladder, formed as an overgrown polyp in the shape of a closed bag. Some individuals are "left-sided", while others are "right-sided." The "left-sided" individual drifts at an angle of 45 degrees to the right of the direction from which the wind is blowing, and the "right-sided" individual does the opposite.

An individual is actually a colony of unisexual organisms. Every individual has specific gonozooids (sex organs or reproductive parts of the animals, either male or female). Each gonozooid is comprised of gonophores, which are little more than sacs containing either ovaries or testes. Physalia are dioecious. Their larvae probably develop very rapidly to small floating forms.
Fertilization is assumed to occur in the open water, because gametes from the gonozooids are shed into the water. This may happen as gonozooids themselves are broken off and released from the colony. The release of gonozooids may be a chemical response occurring when groups of individuals are present in one locality. Critical density is probably required for successful fertilization. Fertilization may take place close to the surface.
Germ Cell Development: Each gonophore has a central spadix of multinucleate endodermal cells separating the coelenteron from a layer of germ cells. Covering each germ cell is a layer of ectodermal tissue. When gonophores first bud, the germ layer is a cap of cells on top of the endodermal spadix. As gonophores mature, the germ cells develop into a layer covering the spadix. Spermatogonia form a thick layer, while oogonia form a convoluted band several cells wide, but only one cell layer thick. There is very little cytoplasmic material within these cells, except during rare instances when cell division is occurring. Oogonia begin development at approximately the same size as spermatogonia, but become considerably larger. All oogonia are apparently formed at an early stage of gonophore development prior to the occurrence of enlargement. Interestingly, there appears to be yolk globules within the cytoplasm of most oogonia.

Synonym (s)
Physalia utriculus Bibelow, 1911
Physalia physalis (Linnaeus, 1758)
(Senior synonym)

Common Name (s)
• Portuguese Man Of War (English)
Economic Importance and Threats
Importance:  Commercial, Dangers
(Affects tourists on the beaches by causing stings (of neurotoxins) from its cnidocytes which gives inflammatory response due to the release of histamines from mast cells.)

Habitat:  Pelagic, Coastal
Prey:  Fish, shrimp, other crustaceans, and other small animals in the plankton.
Predator:  Crustaceans and fish


• West Bengal, Digha Coast (Lat: 21.61) (Long: 87.53) INDIA
• Bay of Bengal
• Arabian Sea
• Tamil Nadu, Chennai Coast INDIA
• East Coast INDIA
• West Bengal, Medinipur INDIA

Literature Source(s)
  • Daniel, R (1985) Fauna of India and the adjacent countries (Coelenterata: Hydrozoa: Siphonophora) ZSI 440 pp Available at - NIO, Goa
  • Zoological Survey of India (Eds) (1991) Animal resources of India (Protozoa to Mammalia) ZSI 1-694 Available at - NCL, Pune
  • Russell, FE and Nagabhushanam, R (1996) Minor phyla in the venomous and poisonous marine invertebrates of the Indian Ocean 1-271 Available at - NIO, Goa
  • Ramakrishna; Sarkar, J and Talukdar, S (2003) Marine invertebrates of Digha coast and some recomendations on their conservation Records of the Zoological Survey of India ZSI, Kolkata 101(3-4) 1 Available at - NCL, Pune
  • Conway, DVP; White, RG; Hugues-Dit-Ciles, J; Gallienne, CP and Robins, DB (2003) Guide to the coastal and surface zooplankton of the south western Indian Ocean Occasional publication no 15 Marine Biological Association of the United Kingdom Occasional Publication of the Marine Biological association of the United Kingdom 354 pp Available at -
  • Daniel, R and Daniel, A (1969) Siphonophora collected during the 35th cruise of the R. V. VITYAZ in the eastern part of the Indian Ocean Symposium on Indian Ocean, Part II 571-574 Available at - Library, CAS, Parangipettai
  • Fernando, AS and Fernando, OJ (2002) A field guide to the common invertebrates of the east coast of India Centre of Advanced Study in Marine Biology 1-258 Available at - NIO, RC Kochi
  • Goswami, BCB (1992) Marine fauna of Digha coast of West Bengal, India Journal of Marine Biological Association of India The Marine Biological Association of India, Cochin 34 115-137 Available at - NIO, RC Kochi
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Sealifebase Available at -
  • Myers, P; Espinosa, R; Parr, CS; Jones, T; Hammond, GS and Dewey, TA (2006) Animal diversity web Available at -
  • Dr. Ramesh, R; Dr. Nammalwar, P and Dr. Gowri, VS (2008) Database on coastal information of Tamil Nadu Report Submitted to Environmental Information System (ENVIS) Centre, Department of Environment, Government of Tamil Nadu Institute for Ocean Management, Anna University, Chennai, Tamil Nadu. Available at -
  • Daniel, R and Daniel, A (1963) On the siphonophores of the Bay of Bengal I.Madras coast2( Journal of the Marine Biological Association of India The marine biological association of India 5(2) 185-220 Available at - NIO, Goa
  • Mitra, S (2010) Cnidarian fauna in Wetlands of West Bengal Journal of Environment and Sociobiology Social Environmental and Biological Association, Kolkata, India 7(2) 133-139 Available at - NIO,Goa

Page last updated on:2011-10-19

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