''Porpita porpita'', or blue button, is a marine organism consisting of a colony of

hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater '' Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds ...

found in the warmer,

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and sub-tropical waters of the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

, Atlantic, and Indian oceans, as well as the Mediterranean Sea and eastern Arabian Sea.Gul, Shahnawaz & Gravili, Cinzia. (2014). On the occurrence of Porpita porpita (Cnidaria: Hydrozoa) at Pakistan coast (North Arabian Sea). Marine Biodiversity Records. 7. 10.1017/S1755267214000189. It was first identified by Carl Linnaeus in 1758, under the basionym ''Medusa porpita''.Lillo, Antonio & Tiralongo, Francesco & Tondo, Elena. (2019). New Records of Porpita porpita (Linnaeus, 1758) (Cnidaria: Hydrozoa) in the Mediterranean Sea. Natural and Engineering Sciences. 4. 293-298. 10.28978/nesciences.646425.Calder, Dale. (2010). Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago. Zootaxa. 2590. 10.11646/zootaxa.2590.1.1. In addition, it is one of the two genera under the suborder Chondrophora, which is a group of cnidarians that also includes ''

Velella ''Velella'' is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is ''Velella velella'', a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raf ...

''.Deidun, Alan. “NOTES ON THE RECENT OCCURRENCE OF UNCOMMON PELAGIC ‘JELLYFISH’ SPECIES IN MALTESE COASTAL WATERS.” Naturalisa Siciliano, vol. 4, no. 34, ser. 3-4, 2010, pp. 375–384. 3-4. The chondrophores are similar to the better-known

siphonophores Siphonophorae (from Greek ''siphōn'' 'tube' + ''pherein'' 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 specie ...

, which includes the

Portuguese man o' war The Portuguese man o' war (''Physalia physalis''), also known as the man-of-war, 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 or blue bottle, which is ...

, or ''Physalia physalis''. Although it is superficially similar to a

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

, each apparent individual is actually a colony of

hydrozoan Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized ...

polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) end is ...

. The taxonomic class, Hydrozoa, falls under the phylum Cnidaria, which includes anemones, corals, and jellyfish, which explains their similar appearances.

Description

The blue button can grow up to 30 mm in diameter and lives on the surface of the sea and consists of two main parts: the float and the hydroid colony. The hard golden brown float is round, almost flat, and about one inch wide. The float organ is responsible for the organism’s vertical movement and also contains pores that are able to communicate with other ''P. porpita'' organisms as well as its surroundings. The hydroid colony, which can range from bright blue turquoise to yellow, resembles tentacles like those of the jellyfish. Each strand has numerous branchlets, each of the knobs of stinging cells called

nematocysts A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...

terminates at the distal end. The blue button has a single mouth located beneath the float, which is used for both the intake of prey and the expulsion of wastes. The mouth is surrounded by a ring of gonozooids and dactylozooids. Tentacles are only found on the dactylozooids, which exist furthest away from the mouth, towards the outer part of the hydroid colony.

Habitat and feeding

The blue button is a part of the

neustonic Neuston, also known as pleuston, are organisms that live at the surface of the ocean or an estuary, or at the surface of a lake, river or pond. Neuston can live on top of the water surface or may be attached to the underside of the water surface. ...

food web, which covers the organisms that inhabit the region on or near the surface of the ocean. This is because it is a passive drifter, which means that it relies on water currents and wind to carry it through the ocean. It is preyed on by the sea slug ''

Glaucus atlanticus ''Glaucus atlanticus'' (common names include the blue sea dragon, sea swallow, blue angel, blue glaucus, dragon slug, blue dragon, blue sea slug and blue ocean slug) is a species of small, blue sea slug, a pelagic (open-ocean) aeolid nudibran ...

'' (sea swallow or blue dragon), violet sea-snails of the genus ''

Janthina ''Janthina'' is a genus of small to medium-sized pelagic or planktonic sea snails, marine gastropod molluscs in the family Epitoniidae.Gofas, S. (2011). Janthina Röding, 1798. Accessed through: World Register of Marine Species at http://www.mari ...

'', and the other blue dragon, ''

Glaucus marginatus ''Glaucus marginatus'' is a species of small, floating, blue sea slug; a pelagic (open-ocean) aeolid nudibranch; a marine opisthobranch gastropod mollusc in the family Glaucidae.Valdés A. & Campillo O.A. (2004) ''Systematics of pelagic aeo ...

''. Unlike ''Velella'', which prefers a passive diet, ''Porpita'' will hunt active crustaceans like crab and fish. It competes with other drifters for food and mainly feeds on

copepods Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have p ...

and crustacean larvae. File:Blue Button Porpita Porpita Uthandi Jan21 D72 19405.jpg, left, Central disk of blue button
1.5cm diameter File:(Porpita porpita) Blue button at Thotlakonda Beach 06.JPG, Blue button from Bay of Bengal File:(Porpita porpita) Blue button, found on Uttorda Beach, Goa, India.jpg, Blue button from Arabian Sea

Commensalism with a fish

Young ''

Carangoides malabaricus The Malabar trevally (''Carangoides malabaricus''), also known as the Malabar jack, Malabar kingfish or nakedshield kingfish, is a species of large inshore marine fish of the jack family, Carangidae. It is distributed throughout the Indian and ...

'', also known as the ‘Malabar trevally’, have been shown to take shelter underneath the floats of ''Porpita porpita''. When removed from its host, the fish will panic. These juvenile fish also appear to show preference for a particular siphonophore. When two pairs of ''Porpita porpita'' and ''Carangoides malabaricus'' are separated by species, then returned to the same tank, each fish will return to its respective partner.

Effects of global warming

The blue button sting is not powerful but may cause slight irritation to human skin. However, in recent years, it has been hypothesized that due to global warming, ''Porpita pacifica'' (another name for the species) colonies have begun appearing in larger numbers along coastlines in Japan and the first case of contact dermatitis from this species was recorded. A sudden increase in the abundance of ''Porpita porpita'' has also been observed in a separate study of its populations in the Ionian and Adriatic seas, possibly also due to rising temperatures throughout the oceans.Bianchi, C.N. (2007). "Biodiversity issues for the forthcoming tropical Mediterranean Sea". Hydrobiologia, 580: pp.7-21.

References

{{Taxonbar, from=Q2535508 Porpitidae Animals described in 1758 Taxa named by Carl Linnaeus