Velella

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Velella
Velella Bae an Anaon.jpg
Close-up of a Velella velella colony
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Order: Anthoathecata
Family: Porpitidae
Genus: Velella
Lamarck, 1801 [1]
Species:
V. velella
Binomial name
Velella velella
Synonyms
List

(Genus)

  • ArmenistaHaeckel, 1888
  • RatariaEschscholtz, 1829
  • VelariaHaeckel, 1888

(Species)

  • Armenista sigmoidesHaeckel, 1888
  • Holothuria spiransForsskål, 1775
  • Medusa pocillumMontagu, 1815
  • Medusa velellaLinnaeus, 1758
  • Rataria cordataEschscholtz, 1829
  • Rataria mitrataEschscholtz, 1829
  • Velella antarcticaEschscholtz, 1829
  • Velella auroraEschscholtz, 1829
  • Velella australisde Haan, 1827
  • Velella caurinaEschscholtz, 1829
  • Velella cyaneaLesson, 1826
  • Velella emarginataQuoy & Gaimard, 1824
  • Velella indicaEschscholtz, 1829
  • Velella lataChamisso & Eysenhardt, 1821
  • Velella limbosaLamarck, 1816
  • Velella meridionalisFewkes, 1889
  • Velella muticaLamarck, 1801
  • Velella oblongaChamisso & Eysenhardt, 1821
  • Velella oxyothoneBrandt, 1835
  • Velella pacificade Haan, 1827
  • Velella patellarisBrandt, 1835
  • Velella pyramidalisCranch, 1818
  • Velella radackianade Haan, 1827
  • Velella sandwichianade Haan, 1827
  • Velella scaphidiaPeron & Lesueur, 1807
  • Velella septentrionalisEschscholtz, 1829
  • Velella sinistraChamisso & Eysenhardt, 1821
  • Velella tentaculataLamarck, 1801
  • Velella tropicaEschscholtz, 1829

Velella is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is Velella velella, [2] a cosmopolitan (widely distributed) free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raft, by-the-wind sailor, purple sail, little sail, or simply Velella. [3]

Contents

This small cnidarian is part of a specialised ocean surface community that includes the better-known cnidarian siphonophore, the Portuguese man o' war. Specialized predatory gastropod molluscs prey on these cnidarians. Such predators include nudibranchs (sea slugs) in the genus Glaucus [4] and purple snails in the genus Janthina . [5]

Each apparent individual is a hydroid colony, and most are less than about 7 cm long. They are usually deep blue in colour, but their most obvious feature is a small stiff sail that catches the wind and propels them over the surface of the sea. Under certain wind conditions, they may be stranded by the thousand on beaches. [6]

Like other Cnidaria, Velella velella are carnivorous. They catch their prey, generally plankton, by means of tentacles that hang down in the water and bear cnidocysts (also called nematocysts). The toxins in their nematocysts are effective against their prey. While cnidarians all possess nematocysts, in some species the nematocysts and toxins therein are more powerful than other species. V. velella's nematocysts are relatively benign to humans, although each person may respond differently to contact with the nematocyst toxin. It is wise to avoid touching one's face or eyes after handling V. velella, and itching may develop on parts of the skin that have been exposed to V. velella nematocysts.

Stranded Velella Vellae.jpg
Stranded Velella
Velella close-up Velella in California April 2020.jpg
Velella close-up

Distribution and habitat

Velella velella lives in warm and temperate waters in all the world's oceans. They live at the water/air interface, with the float above the water, and polyps hanging down about a centimetre below. Organisms that live partly in and partly out of the water like this are known as neuston. [7] Offshore boaters sometimes encounter thousands of V. velella on the water surface.[ citation needed ]

The small rigid sail projects into the air and catches the wind. However, Velella sails always align along the direction of the wind where the sail may act as an aerofoil, so that the animals tend to sail downwind at a small angle to the wind. [8] Having no means of locomotion other than its sail, V. velella is at the mercy of prevailing winds for moving around the seas, and are thereby also subject to mass-strandings on beaches throughout the world. For example, a mass stranding occurs most years in the spring along the West Coast of North America, from British Columbia to California, beginning in the north and moving south over several weeks' time. In some years, so many animals are left at the tide line by receding waves, that the line of dying (and subsequently rotting) animals may be many centimetres deep, along hundreds of kilometres of beaches.[ citation needed ] Mass strandings have been reported also on the west coast of Ireland, [9] and in Hayle, on the west coast of Cornwall in England. [10]

Velella (by-the-wind sailors) stranded on Rodeo Beach, Marin County, California. Vellelawholebeach.jpg
Velella (by-the-wind sailors) stranded on Rodeo Beach, Marin County, California.

Life cycle

Like many Hydrozoa, Velella velella has a bipartite life cycle, with a form of alternation of generations. The deep blue, by-the-wind sailors that are recognized by many beach-goers are the polyp phase of the life cycle. Each "individual" with its sail is really a hydroid colony, with many polyps that feed on ocean plankton. These are connected by a canal system that enables the colony to share whatever food is ingested by individual polyps. Each by-the-wind sailor is a colony of all-male or all-female polyps. The colony has several different kinds of polyps, some of which are both feeding and reproductive, called gonozooids, and others protective, called dactylozooids. [11]

The gonozooids each produce numerous tiny jellyfish by an asexual budding process, so that each Velella colony produces thousands of tiny jellyfish (medusae), each about 1 mm high and wide, over several weeks. The tiny medusae are each provided with many zooxanthellae, single-celled endosymbiotic organisms typically also found in corals and some sea anemones, that can utilize sunlight to provide energy to the jellyfish. Curiously, although a healthy captive Velella will release many medusae under the microscope, and are expected to do the same in the sea, the medusae of Velella are rarely captured in the plankton and very little is known about their natural history. The medusae develop to sexual maturity within about three weeks in the laboratory and their free-spawned eggs and sperm develop into a planktonic larva called a conaria, which develops into a new floating Velella hydroid colony. [11]

Systematics

Velella velella & Palmaria palmata in a tidepool, Cambria, California Velella velella & Palmaria palmata.JPG
Velella velella & Palmaria palmata in a tidepool, Cambria, California

The Porpitidae is a family of the Hydrozoa erected for two genera of hydroids that live floating free at the surface of the open ocean: Velella and Porpita. The systematic position of these peculiar genera has long been a topic of discussion among taxonomists who work with pelagic Cnidaria. The three genera[ clarification needed ] were put in with athecate hydroids in the mid-to-late 19th century by some, whereas other authors at the time included them in the Siphonophorae. A new order was established for these genera by Totton, [12] in 1954, called the Chondrophora, while at the same time, other authors favored again placing them in the Anthomedusae/Athecatae. [11] Most authors in the past 40 years have accepted interpretation of these animals as unusual floating colonial athecate hydroids, which produce medusae clearly belonging in the Anthomedusae. Although the exact position of the family Porpitidae within the Athecatae/Anthomedusae is not yet clear, the order Chondrophora is no longer used by hydrozoan systematists.[ citation needed ]

See also

Related Research Articles

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Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in fresh water and marine environments, including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites. Their distinguishing features are a decentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living, jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Cnidarians are also some of the only animals that can reproduce both sexually and asexually.

<span class="mw-page-title-main">Jellyfish</span> Soft-bodied, aquatic invertebrates

Jellyfish, also known as sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.

<span class="mw-page-title-main">Scyphozoa</span> Class of marine cnidarians, true jellyfish

The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish.

<span class="mw-page-title-main">Portuguese man o' war</span> Marine invertebrate

The Portuguese man o' war, also known as the man-of-war or bluebottle, 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 bluebottle, 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.

<span class="mw-page-title-main">Hydrozoa</span> Class of cnidarians

Hydrozoa is 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 individual animals cannot survive outside the colony. A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.

<i>Obelia</i> Genus of hydrozoans

Obelia is a genus of hydrozoans, a class of mainly marine and some freshwater animal species that have both polyp and medusa stages in their life cycle. Hydrozoa belongs to the phylum Cnidaria, which are aquatic organisms that are relatively simple in structure with a diameter around 1mm. There are currently 120 known species, with more to be discovered. These species are grouped into three broad categories: O. bidentata, O. dichotoma, and O. geniculata. O. longissima was later accepted as a legitimate species, but taxonomy regarding the entire genus is debated over.

<span class="mw-page-title-main">Chondrophore</span> Small group of hydrozoans comprising the family Porpitidae

The chondrophores or porpitids are a small group of hydrozoans in the family Porpitidae. Though it derives from an outdated name for this lineage, some still find the term 'chondrophore' useful as a synonym to 'porpitid' in discussions of the two genera contained therein, Porpita and Velella.

<span class="mw-page-title-main">Medusozoa</span> Clade of marine invertebrates

Medusozoa is a clade in the phylum Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa. Medusozoans are distinguished by having a medusa stage in their often complex life cycle, a medusa typically being an umbrella-shaped body with stinging tentacles around the edge. With the exception of some Hydrozoa, all are called jellyfish in their free-swimming medusa phase.

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<span class="mw-page-title-main">Anthoathecata</span> Order of hydrozoans which always have a polyp stage

Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known and heavily discussed group. It has also been called Gymnoblastea and, Anthomedusa, Athecata, Hydromedusa, and Stylasterina. There are about 1,200 species worldwide.

<span class="mw-page-title-main">Hydroidolina</span> Subclass of hydrozoans

Hydroidolina is a subclass of Hydrozoa and makes up 90% of the class. Controversy surrounds who the sister groups of Hydroidolina are, but research has shown that three orders remain consistent as direct relatives: Siphonophorae, Anthoathecata, and Leptothecata.

<span class="mw-page-title-main">Leptothecata</span> Order of cnidarians with hydrothecae

Leptothecata, or thecate hydroids, are an order of hydrozoans in the phylum Cnidaria. Their closest living relatives are the athecate hydroids, which are similar enough to have always been considered closely related, and the very apomorphic Siphonophorae, which were placed outside the "Hydroida". Given that there are no firm rules for synonymy for high-ranked taxa, alternative names like Leptomedusa, Thecaphora or Thecata, with or without the ending emended to "-ae", are also often used for Leptothecata.

<i>Porpita porpita</i> Species of hydrozoan

Porpita porpita, or the blue button, is a marine organism consisting of a colony of hydroids found in the warmer, tropical and sub-tropical waters of the Pacific, Atlantic, and Indian oceans, as well as the Mediterranean Sea and eastern Arabian Sea. It was first identified by Carl Linnaeus in 1758, under the basionym Medusa porpita. In addition, it is one of the two genera under the suborder Chondrophora, which is a group of cnidarians that also includes Velella. The chondrophores are similar to the better-known siphonophores, which includes the Portuguese man o' war, or Physalia physalis. Although it is superficially similar to a jellyfish, each apparent individual is actually a colony of hydrozoan polyps. The taxonomic class, Hydrozoa, falls under the phylum Cnidaria, which includes anemones, corals, and jellyfish, which explains their similar appearances.

Bougainvillia aberrans is a marine invertebrate, a species of hydroid in the suborder Anthomedusae. It was first described by Dale Calder in 1993. They have four radical clusters of marginal tentacles. Bougainvillia aberrans is found in Bermuda in the western North Atlantic Ocean.

<i>Eudendrium ramosum</i> Species of hydrozoan

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<i>Apolemia</i> Family of cnidarians

Apolemia is a genus of siphonophores. It is the only genus in the monotypic family Apolemiidae.

Jean Bouillon was a Belgian marine biologist and expert on Hydrozoa.

<i>Porpita prunella</i> Species of hydrozoan

Porpita prunella is a marine species of hydrozoan organisms within the family Porpitidae. It consists of colonies of zooids. Very little is known about this species, as there have been no confirmed sightings since its discovery in 1801 and naming by Haeckel in 1888. Being in the chondrophore group, it is likely that its behaviour is similar to the other species of the genera in the family. However there are also serious doubts as to its very existence as a separate species and may in fact be a synonym for Porpita porpita instead.

<i>Tima nigroannulata</i> Species of hydrozoa

Tima nigroannulata, commonly known as the elegant jellyfish, is a recently discovered colonial hydrozoa found on the Pacific coast of Japan.

References

  1. Lamarck, J. B. (1801). Système des animaux sans vertèbres. Paris, France: by the author and Deterville. p. 555 via Biodiversity Heritage Library.
  2. Schuchert P, ed. (2013). "Velella velella (Linnaeus, 1758)". World Hydrozoa database. World Register of Marine Species . Retrieved 23 April 2013.
  3. Harrington Wells (1937). Seashore Life. Wagner Publishing Company, USA (see pages 138 and 144 in the 1942 edition)
  4. Gosliner, T.M. (1987). Nudibranchs of Southern Africa page 127, ISBN   0-930118-13-8
  5. Branch, G.M., Branch, M.L, Griffiths, C.L. and Beckley, L.E. (2010). Two Oceans: a guide to the marine life of southern Africa. Cape Town:Struik Nature. page 188. ISBN   9781770077720.
  6. "By-the-wind-sailors: Creatures wash up on Guernsey beaches". BBC News. 2024-04-22. Retrieved 2024-04-23.
  7. "Uncovering the Neuston, a Mysterious Living Island of Sea Creatures". NPR. 2021-05-09. Retrieved 2023-05-21.
  8. McNeill Alexander, R. (2002). Principles of Animal Locomotion. Princeton University Press. ISBN   0-691-08678-8.
  9. Delap, M. J. (1921). "Drift on the Kerry coast". The Irish Naturalist . 30 (3): 40. JSTOR   25525026.
  10. "'Thousands' of jellyfish-like creatures swamp beach". 4 July 2022.
  11. 1 2 3 A. Brinckmann-Voss (1970). Anthomedusae/Athecatae (Hydrozoa, Cnidaria) of the Mediterranean. Part I. Capitata. Fauna e Flora del Golfo di Napoli. Vol. 39. Stazione Zoologica. pp. 1–96, 11 pls.
  12. Totton, A. K. (1954). "Siphonophora of the Indian Ocean: Together with Systematic and Biological Notes on Related Specimens from Other Oceans". Discovery Reports. 27: 1–162 [30, 33]. OCLC   14100651.