| Paranthus rapiformis | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hexacorallia |
| Order: | Actiniaria |
| Family: | Actinostolidae |
| Genus: | Paranthus |
| Species: | P. rapiformis |
| Binomial name | |
| Paranthus rapiformis | |
| Synonyms [2] | |
| |
Paranthus rapiformis, the onion anemone, is a species of sea anemone in the family Actinostolidae. It was first described by the French naturalist Charles Alexandre Lesueur in 1817 and is native to the northwestern Atlantic Ocean and the Gulf of Mexico. [2]
P. rapiformis is a small white sea anemone which burrows into the sediment, usually subtidally, but it may be exposed at extreme low water. The base of the column is expanded which anchors it in place, and it is usually attached to a submerged stone or shell. When covered with water, the short tentacles spread out over the surface of the sand. [3] When it is disturbed, the tentacles retract and the column inflates to form a globular shape; this is translucent, with longitudinal white stripes, and resembles a small onion. [4]
As a burrowing sea anemone, the pedal disc of P. rapiformis is replaced by a rounded end known as a "physa" which is used for digging. First the physa is pushed into the soft sediment, then the anemone swells its body wall to anchor itself in place while pushing the physa further into the sand. Now it inflates the physa and deflates the body wall, using its strong longitudinal muscles to draw the upper part towards the base, during which process, the physa inverts. These two steps are repeated as it works its way deeper into the sediment. [4]
The burrow is cylindrical and the vertical sides are lined with mucus; it is commonly 8 cm (3 in) long and 2.5 cm (1 in) wide, but can be much larger, however it collapses if the sea anemone is removed. A dislodged anemone may adopt a globular shape and be rolled about on the sand by the sea until it finds a less turbulent place where it can burrow. [5]
Anthozoa is a subphylum of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new polyps from an original, founding individual. Colonies are strengthened by calcium carbonate and other materials and take various massive, plate-like, bushy or leafy forms.
The starlet sea anemone is a species of small sea anemone in the family Edwardsiidae native to the east coast of the United States, with introduced populations along the coast of southeast England and the west coast of the United States. Populations have also been located in Nova Scotia, Canada. This sea anemone is found in the shallow brackish water of coastal lagoons and salt marshes where its slender column is usually buried in the mud and its tentacles exposed. Its genome has been sequenced and it is cultivated in the laboratory as a model organism, but the IUCN has listed it as being a "Vulnerable species" in the wild.
Sea anemones are a group of predatory marine invertebrates of the order Actiniaria. Because of their colourful appearance, they are named after the Anemone, a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.
Phymanthus crucifer, commonly known as rock flower anemone, flower anemone, red beaded anemone or the beaded anemone, is a species of sea anemone in the family Phymanthidae. It has been described as "closely similar" to Heteractis aurora in several ways, commonly exhibiting "tentacles with swollen cross-bars" bearing large clusters of stinging nematocysts. However, P. crucifer may also be found with smooth tentacles, sometimes in the immediate vicinity of a swollen-crossbarred specimen.
Peachia cylindrica is a large species of sea anemone in the family Haloclavidae. It is normally found burrowed into soft substrates, the only visible part of the animal being the oral disc and tentacles which usually lie flat on the sand. It is the type species of the genus Peachia.
Calliactis tricolor, the tricolor anemone or hitchhiking anemone, is a species of sea anemone in the family Hormathiidae. It occurs in the Caribbean Sea and the Gulf of Mexico. It can be found attached to rocks but is often attached to a living crab or mollusc or an empty shell occupied by a hermit crab.
Cerianthus lloydii is a species of tube-dwelling sea anemone in the family Cerianthidae. It is sometimes called the lesser cylinder anemone and is found in shallow seas around the coasts of north west Europe.
Lebrunia neglecta is a species of sea anemone in the family Aliciidae. It is found in the Caribbean Sea and Gulf of Mexico.
Heteractis malu, also known as the malu anemone, delicate sea anemone or white sand anemone, is a species of sea anemone in the family Stichodactylidae.
Urticina columbiana, common names crusty red anemone, Columbia sand anemone, sand anemone, and the sand-rose anemone, is a species of sea anemone in the family Actiniidae.
Anthopleura ballii, commonly known as the red speckled anemone, is a species of sea anemone in the family Actiniidae. It is found in shallow water in the northeastern Atlantic Ocean.
Anthopleura thallia, commonly known as the glaucous pimplet, is a species of sea anemone in the family Actiniidae. It is found in shallow water in the northeastern Atlantic Ocean and the Mediterranean Sea.
Pleurobrachia pileus is a species of comb jelly, commonly known as a sea gooseberry. It is found in open water in the northern Atlantic Ocean, the North Sea, the Baltic Sea and the Black Sea, and was first described by the Danish zoologist Otto Friedrich Müller in 1776.
Actinothoe sphyrodeta, the sandalled anemone, is a small sea anemone in the family Sagartiidae. It is native to the northeastern Atlantic Ocean and is common on the north, west and south coasts of Britain. It is usually grey or whitish but may have an orange oral disc. The translucent white tentacles that grow around the edge of the oral disc can number up to 120.
Haloclava producta is a species of sea anemone in the family Haloclavidae, commonly known as the ghost anemone. This species is native to shallow water in the northwestern Atlantic Ocean, between Cape Hatteras and the Bay of Fundy, where it makes a temporary burrow in soft sediment. It is found on sand flats, both intertidally and subtidally.
Mesacmaea mitchellii is a species of sea anemone in the family Haloclavidae. It is found in the northeastern Atlantic Ocean and the Mediterranean Sea where it burrows in soft sediment.
Edwardsia neozelanica, commonly known as the burrowing anemone, is a small cryptic sea anemone from New Zealand. It burrows into soft mud or sand, and when covered with water extends its tentacles to feed on tiny particles of detritus.
Anthopleura artemisia is a species of sea anemone. It is known by a number of common names, including burrowing anemone and moonglow anemone. It was first described to science in 1846 in a volume by James Dwight Dana, reporting on the animals found on the United States Exploring Expedition. Dana attributes the description to Charles Pickering, who was a naturalist on the expedition.
Actinostella flosculifera, the collared sand anemone, is a species of sea anemone in the family Actiniidae. It is found semi-immersed in the sediment in shallow water in the tropical and subtropical Atlantic Ocean.
Alpheus armatus is a species of snapping shrimp in the family Alpheidae, found in shallow water in the Caribbean Sea and the Gulf of Mexico. It lives in association with a sea anemone such as Bartholomea annulata, clearing out sand from the cracks and crevices in which the sea anemone often lives.