| Odontaster validus | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Asteroidea |
| Order: | Valvatida |
| Family: | Odontasteridae |
| Genus: | Odontaster |
| Species: | O. validus |
| Binomial name | |
| Odontaster validus Koehler, 1906 [1] | |
| Synonyms [1] | |
| |
Odontaster validus is a species of sea star in the family Odontasteridae. Its range includes the Southern Ocean and the seas around the mainland and islands of Antarctica.
Odontaster validus can grow to about 10 cm (4 in) in diameter. The disc is broad, thick and cushion-like, creased by interambulacral grooves. There is a large madreporite near the centre and the surface is covered in small granulations organised in radial rows. The five short arms are wide at the base tapering sharply and the tip is often raised off the substrate showing the pale coloured tube feet beneath. The colour of the upper or aboral surface is plain red while the underside is pink. [1]
Odontaster validus is the most common sea star found in Antarctica. Its range includes the Antarctic Peninsula, the South Shetland Islands, the South Orkney Islands, South Georgia and the South Sandwich Islands, the Shag Rocks, the Prince Edward Islands and Bouvet Island. It is found at depths down to 900 metres. [2]
Odontaster validus is an omnivorous scavenger and consumes anything it finds including carrion, detritus, the faeces of seals, red algae, bivalve shells, sponges, hydroids, other sea star, sea urchins, isopods, bryozoans, amphipods, crustacean larvae, ostracods, shrimps and diatoms. [2] They have been observed aggregating on banks of mussels that have been exposed and damaged and on injured sea star, Acodontaster conspicuus . [3] In turn, they are preyed upon by sea anemones and other species of sea star. [2] It is an ecologically important species because of its consumption of benthic larvae and the control it exerts on the sea star Acodontaster conspicuus and the nudibranch Doris spp. which themselves tend to limit the growth of sponges that tend to dominate the seabed. [4]
Odontaster validus takes 3 to 6 years to reach maturity but may live for 100 years. [2] This is a consequence of the animal being cold-blooded, the harsh environmental conditions in which it lives and the low metabolic rate that ensues. [2] In McMurdo Sound, where it has been extensively studied, the water temperature is about −1.8 °C (28.8 °F). [5] The initiation of oogenesis occurs from August to February and the eggs take about 18 months to mature. Spawning takes place between May and September and may be linked to seasonal changes in light levels, sunrise taking place in McMurdo Sound in August. [5] The larval development is also slow with the first, bipinnaria, stage lasting 2 months. The larvae remain near the seabed during this time but become pelagic for up to 6 months as brachiolaria larvae which allows them to disperse widely. They then return to the seabed, undergo metamorphosis and develop into juvenile sea star. [2]
Odontaster validus does not attack members of its own species but can attack sea star of other species. This seems to be due to chemoreceptors which can identify conspecifics by their odour. [6] Sea star often converge on food sources and a study was undertaken to examine how they do this. It was found that food-deprived individual Odontaster validus could distinguish between the odours emitted by satiated and by starved sea star of the same species. They were strongly attracted to the former and took little notice of the latter. [6]
Odontaster validus is much less sensitive to higher water temperatures than the other Antarctic marine species on which it feeds which mostly find temperatures above 3 °C lethal. Even when not killed at higher temperatures, many organisms cease to feed, may remain immobile or fail to reproduce and others started metabolising anaerobically. [7] A study was undertaken to examine the implications of this for the Antarctic marine environment if water temperatures rise as a result of global warming. [7]
Another research study examined the parameters required for successful fertilisation of the eggs of Odontaster validus compared to similar temperate water sea stars. It was found that a density of sperm of 105 sperm per millilitre was sufficient to cause a high proportion of eggs to be fertilised and that this was at least ten times the density required by comparable species in less harsh environments. The sperm still retained a minimal fertilisation ability after 24 hours but had a narrow tolerance to variations in water temperature. [8]
An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
The capelin or caplin is a small forage fish of the smelt family found in the North Atlantic, North Pacific and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat a great deal of krill and other crustaceans. Among others, whales, seals, Atlantic cod, Atlantic mackerel, squid and seabirds prey on capelin, in particular during the spawning season while the capelin migrate south. Capelin spawn on sand and gravel bottoms or sandy beaches at the age of two to six years. When spawning on beaches, capelin have an extremely high post-spawning mortality rate which, for males, is close to 100%. Males reach 20 cm (8 in) in length, while females are up to 25.2 cm (10 in) long. They are olive-coloured dorsally, shading to silver on sides. Males have a translucent ridge on both sides of their bodies. The ventral aspects of the males iridesce reddish at the time of spawn.
Thorson's rule is an ecogeographical rule which states that benthic marine invertebrates at low latitudes tend to produce large numbers of eggs developing to pelagic and widely dispersing larvae, whereas at high latitudes such organisms tend to produce fewer and larger lecithotrophic (yolk-feeding) eggs and larger offspring, often by viviparity or ovoviviparity, which are often brooded.
Limacina rangii is a species of swimming sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies (Thecosomata).
Urticina eques is a species of sea anemone in the family Actiniidae. It is commonly known as the white-spotted rose anemone or strawberry anemone.
Acodontaster conspicuus is a species of starfish in the family Odontasteridae. It is found in the Southern Ocean, in the waters off Antarctica and the island groups nearby.
The Antarctic scallop is a species of bivalve mollusc in the large family of scallops, the Pectinidae. It was thought to be the only species in the genus Adamussium until an extinct Pliocene species was described in 2016. Its exact relationship to other members of the Pectinidae is unclear. It is found in the ice-cold seas surrounding Antarctica, sometimes at great depths.
Sterechinus neumayeri, the Antarctic sea urchin, is a species of sea urchin in the family Echinidae. It is found living on the seabed in the waters around Antarctica. It has been used as a model organism in the fields of reproductive biology, embryology, ecology, physiology and toxicology.
Laternula elliptica is a species of saltwater clam, a marine bivalve mollusc in the family Laternulidae, the lantern shells. It is the largest bivalve found under the surface of the seabed in the Southern Ocean.
Homaxinella balfourensis is a species of sea sponge in the family Suberitidae. It is found in the seas around Antarctica and can grow in two forms, either branching out in one plane like a fan or forming an upright club-like structure.
The ocellated icefish is a fish of the family Channichthyidae. It lives in the cold waters off Antarctica and is known for having transparent haemoglobin-free blood.
The wildlife of Antarctica are extremophiles, having adapted to the dryness, low temperatures, and high exposure common in Antarctica. The extreme weather of the interior contrasts to the relatively mild conditions on the Antarctic Peninsula and the subantarctic islands, which have warmer temperatures and more liquid water. Much of the ocean around the mainland is covered by sea ice. The oceans themselves are a more stable environment for life, both in the water column and on the seabed.
The emerald rockcod, also known as the emerald notothen is a species of marine ray-finned fish belonging to the family Nototheniidae, the notothens or cod icefishes. It is native to the Southern Ocean where it is a commercially important species.
Diplasterias brucei is a species of starfish in the family Asteriidae. It is found in the Pacific Ocean and Southern Ocean. It is a predator and scavenger and is unusual among starfish in that it broods its young.
Phyllophora antarctica is a species of red alga in the family Phyllophoraceae. It is native to Antarctica where it grows in dim light on the underside of sea ice. Some of it becomes detached and accumulates in drifts on the seabed. Many different organisms live attached to the fronds or among them.
Notothenia coriiceps, also known as the black rockcod, Antarctic yellowbelly rockcod, or Antarctic bullhead notothen, is a species of marine ray-finned fish, belonging to the family Nototheniidae, the notothens or cod icefishes. It is widely spread around the Antarctic continent. Like other Antarctic notothenioid fishes, N. coriiceps evolved in the stable, ice-cold environment of the Southern Ocean. It is not currently targeted by commercial fisheries.
Tritoniella is a genus of sea slugs, specifically dendronotid nudibranchs. It is a marine gastropod mollusc in the family Tritoniidae.The genus was described in 1907 by the British diplomat and malacologist Charles Eliot.
Clavularia frankliniana is a species of colonial soft coral in the family Clavulariidae. It is found in the southern Atlantic Ocean and the waters around Antarctica. It was first described in 1902 by the French zoologist Louis Roule.
Euchaetidae is a family of marine copepods. The family is cosmopolitan and occurs in all the oceans, including the Southern and Arctic Oceans. Euchaetidae are medium to large-sized copepods.
Scottnema lindsayae is a species of nematode belonging to the family Cephalobidae. First described in 1971, it is endemic to Antarctica and most commonly found in the McMurdo Dry Valleys. S. lindsayae, a microscopic worm, feeds on microbes, including bacteria, yeast, and algae. Adapted to very cold and dry climates, its population may be decreasing as a result of climate change.