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(invertebrate zoology)
An order of the cnidarian class Hydrozoa characterized by the complex organization of components which may be connected by a stemlike region or may be more closely united into a compact organism.



a subclass or, according to another taxo-nomic system, an order of free-swimming marine coelenterates of the class Hydrozoa. The body, which ranges in length from 1 cm to 3 m, is generally colorless and transparent. Only a few species are brightly colored. Siphonophorans form polymorphic colonies whose individuals, polyps and medusae, differ in structure and are converted into organs of the colony. At the apex there is usually a swim bladder, or pneumatophore, with gas, chiefly nitrogen, which is released by the gas gland to help keep the colony vertical. In some siphonophorans, for example, the Physalia, the pneumatophore emerges at the surface of the water and functions as a sail. A colony also consists of nectocalyxes (swimming bells), which are modified medusae whose contractions propel the colony, and feeding polyps (gas-trozooids), which swallow and digest prey and bear a long tentacle (lasso cell) with a group of stinging cells. There also are sexual individuals (gonozooids). Heterogenous members of the colony are usually gathered in aggregates called cormidia. Siphonophorans reproduce sexually; the free-swimming larva, a modified planula, forms a new colony by budding.

Siphonophorans of the order Disconanta are not colonies but solitary free-swimming polyps. Of the 250 species, most inhabit tropical seas. Only two species, one from each of the genera Dimophyes and Physophora, are found in the USSR. Some large tropical siphonophorans, for example, the Portuguese man-of-war (Physalia), are dangerous to man; prolonged contact with the long (up to 10 m) tentacles in water causes severe burns and systemic disease with protracted elevation of body temperature.


Dogel’, V. A. “Tip kishechnopolostnykh.” In Rukovodstvo po zoologii, vol. 1. Moscow-Leningrad, 1937. Pages 323-30.
Zhizn’ zhivotnvkh, vol. 1. Moscow, 1968.
Dogel’. V. A. Zoologiia bespozvonochnykh, 6th ed. Moscow, 1975.

A. V. IVANOV [23–1436–]

References in periodicals archive ?
DEEP FEEDING: Gelatinous siphonophores (top), which may be Earth's most abundant predators, capture fish and other prey by unfurling curtains of stinging tentacles; thin as a broomstick, the largest grow longer than blue whales.
The Subantarctic Waters (SAAW) of the Humboldt Current System (HCS) that bathe the Chilean coast have also been affected by these population increases and in several coastal areas of high biological productivity, such as Antofagasta, Valparaiso, and Concepcion, high densities of gelatinous organisms (medusae and siphonophores) have occurred (Palma, 1994; Palma & Rosales, 1995; Palma & Apablaza, 2004; Pavez et al, 2010).
Epipelagic siphonophore assemblages associated with water masses along a transect between Chile and Easter Island (eastern South Pacific Ocean).
This organization was very reminiscent of that in the two siphonophores and of that reported for another hydroid, Coryne (Golz, 1994).
The behavior of ascidian sperm is quite different from that in the siphonophore sperm.
These animals include some radiolarmans and foraminifera, as well as medusae, siphonophores, ctenophores, chaetognaths, pteropods, heteropods, appendicularians, salps, doliolids, and pyrosomes (e.g., Hamner et al., 1975).
Transparency in the Cnidaria is mostly found in cubozoans, hydromedusae, and siphonophores. Cubozoans are all highly transparent (Matsumoto, 1995).
"Ambush" predators (e.g., medusa, siphonophores, cydippid ctenophores) with short sighting distances increase their chances of entangling visually oriented prey before being detected and avoided.
But perhaps among the most curious of all the curious creatures in the twilight zone are siphonophores. They also form gelatinous chains or strings.
They are not "true" jellyfish, but belong to a group of organisms known as siphonophores. The stings are typically mild and can be treated with ice or hot water, however some people had required treatment by paramedics at the weekend, Surf Life Saving Queensland (SLSQ) said.
Although copepods dominated the community in both periods, salps, siphonophores, chaetognaths and decapods, were more abundant during the first period, and because they are larger in size, probably contributed to the observed changes in size structure.
Various pelagic fishes and invertebrates (zooplankton, jellyfish, siphonophores, crustaceans, and polychaetes) have been seen along the ridge, including mesopelagic fishes, freckled driftfish, Psenes cyanophrys, scombrids (juveniles and a large tuna), a thresher shark, Alopias pelagicus, a possible blue shark, and squid, Sthenoteuthis oualaniensis and Onychoteuthis [46, 48, 49].