Thysanoessa | |
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Thysanoessa raschii | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Malacostraca |
Order: | Euphausiacea |
Family: | Euphausiidae |
Genus: | Thysanoessa Brandt, 1851 |
Type species | |
Thysanoessa raschii Michael Sars, 1864 |
Thysanoessa is a genus of the krill [1] that play critical roles in the marine food web. They're abundant in Arctic and Antarctic areas, feeding on zooplankton and detritus to obtain energy. [2] Thysanoessa are responsible for the transportation of carbon and nutrients from surface waters to deeper trophic levels. This genus serves as prey for various fish and provide energy to marine ecosystems as they are at a low trophic level. Most travel through vertical migration, meaning they travel up and down in the water column, providing food for predators at the surface during the night, and at deeper levels during the day.
Longevity in this genus varies depending on the specie. The average lifespan for the Thysanoessa is between three and four years. The development and growth of this organism takes place during winter to autumn. [3] Thysanoessa are broadcast spawners, meaning that the males will physically put their sperm onto the female's body so that the eggs become fertilized as the female releases them. [4] Once released and in the water, the eggs are dispersed and on their own, ready to hatch in the nauplius stage. Female krill lay over 10,000 eggs, sometimes seasonally, resulting in large populations. The Thysanoessa larvae are slender and their carapace is short in early stages. [5] As the body expands, the cephalothorax becomes transparent.
Thysanoessa are decapod crustaceans, meaning that they have five pairs of legs on their three-parted body. The cephalothorax is divided into the head, the thorax, and the pleon. With the help of the legs and two antennae, the krill is able to feed and groom freely. The male species have a "rounded lobe" on the first and second antennae called a setae. The Thysanoessa genus is a bioluminescent organism. They have organs called photophores that undergo an enzymatic chemical reaction. These bioluminescent enzymes derive from the consumption of dinoflagellates, yet the complete role of photophores are still unknown.
At low food concentrations, Thysanoessa has higher feeding rates compared to other krill. Studies have shown that high feeding rates are due to morphology of appendage and stomach content. [6] Thysanoessa have a high content of fatty acid that comes from the consumption of copepods which contain wax-ester. This genus also feeds on decaying plant material from suspended water columns and bottom sediments. The spacing in the appendage of a Thysanoessa allows for different sources of food between species, Many species of Thysanoessa, for instance, T. inermis and T. raschii differentiate in food sources during the winter and spring. [6]
Thysanoessa are found in the Western and Central Barents Sea. Their location varies within species, while some are boreal, others live in a sub-arctic habitat. Shifts in locations are caused by impacts of global warming and severe changes in ocean temperatures. [7] Given this, Arctic habitats are projected to shift vigorously in the next years, impacting krill growth and abundance of nutrients such as chlorophyll a. [8] The movement of krill in various geographic locations result in a movement of energy in the food web. Carbon, caloric, and lipid concentrations vary depending on the specie and the location. Over time, Thysanoessa have been able to adapt to different temperatures in different regions, making their corporal composition change gradually.
Thysanoessa is a genus of krill, containing the following species:
Antarctic krill is a species of krill found in the Antarctic waters of the Southern Ocean. It is a small, swimming crustacean that lives in large schools, called swarms, sometimes reaching densities of 10,000–30,000 individual animals per cubic metre. It feeds directly on minute phytoplankton, thereby using the primary production energy that the phytoplankton originally derived from the sun in order to sustain their pelagic life cycle. It grows to a length of 6 centimetres (2.4 in), weighs up to 2 grams (0.071 oz), and can live for up to six years. It is a key species in the Antarctic ecosystem and in terms of biomass, is one of the most abundant animal species on the planet – approximately 500 million metric tons.
Northern krill is a species of krill that lives in the North Atlantic Ocean. It is an important component of the zooplankton, providing food for whales, seals, fish and birds. M. norvegica is the only species recognised in the genus Meganyctiphanes.
The fin whale, also known as the finback whale or common rorqual, is a species of baleen whale and the second-longest cetacean after the blue whale. The biggest individual reportedly measured 26 m (85 ft) in length, with a maximum recorded weight of 77 to 81 tonnes. The fin whale's body is long, slender and brownish-gray in color, with a paler underside to appear less conspicuous from below (countershading).
Krill(Euphausiids) are small and exclusively marine crustaceans of the order Euphausiacea, found in all the world's oceans. The name "krill" comes from the Norwegian word krill, meaning "small fry of fish", which is also often attributed to species of fish.
The minke whale, or lesser rorqual, is a species complex of baleen whale. The two species of minke whale are the common minke whale and the Antarctic minke whale. The minke whale was first described by the Danish naturalist Otto Fabricius in 1780, who assumed it must be an already known species and assigned his specimen to Balaena rostrata, a name given to the northern bottlenose whale by Otto Friedrich Müller in 1776. In 1804, Bernard Germain de Lacépède described a juvenile specimen of Balaenoptera acuto-rostrata. The name is a partial translation of Norwegian minkehval, possibly after a Norwegian whaler named Meincke, who mistook a northern minke whale for a blue whale.
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.
King crabs are decapod crustaceans in the family Lithodidae that are chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food with the most common being the red king crab.
The krill fishery is the commercial fishery of krill, small shrimp-like marine animals that live in the oceans world-wide. The present estimate for the biomass of Antarctic krill is 379 million tonnes. The total global harvest of krill from all fisheries amounts to 150–200,000 tonnes annually, mainly Antarctic krill and North Pacific krill.
Thysanoessa raschii, sometimes known as Arctic krill, is one of the most common euphausiid species of the subarctic and Arctic seas. They may reach 20–25 millimetres (0.8–1.0 in) long, and are sexually mature above 14 mm (0.6 in).
The stoplight loosejaws are small, deep-sea dragonfishes of the genus Malacosteus, classified either within the subfamily Malacosteinae of the family Stomiidae, or in the separate family Malacosteidae. They are found worldwide, outside of the Arctic and Subantarctic, in the mesopelagic zone below a depth of 500 meters. This genus once contained three nominal species: M. niger, M. choristodactylus, and M. danae, with the validity of the latter two species being challenged by different authors at various times. In 2007, Kenaley examined over 450 stoplight loosejaw specimens and revised the genus to contain two species, M. niger and the new M. australis.
The Pacific ocean perch, also known as the Pacific rockfish, rose fish, red bream or red perch, is a fish whose range spans across the North Pacific : from southern California around the Pacific rim to northern Honshū, Japan, including the Bering Sea. The species appears to be most abundant in northern British Columbia, the Gulf of Alaska, and the Aleutian Islands.
Zhemchug Canyon is an underwater canyon located in the Bering Sea between the Siberian and Alaskan coastlines. It is the deepest submarine canyon in the world with a vertical relief of 8,530 feet and a length of 99 miles . The submarine canyon is renowned for its extraordinary size, hosting a unique marine environment because of its substantial size. It forms a significant portion of the Bering Sea’s ecosystem, contributing to its biological productivity and natural habitat for a diverse range of marine species.
Euphausia crystallorophias is a species of krill, sometimes called ice krill, crystal krill, or Antarctic coastal krill. It lives in the coastal waters around Antarctica, further south than any other species of krill. The specimens for the species' original description were collected through holes cut in the ice by Robert Falcon Scott's Discovery Expedition, several thousand having been donated by Thomas Vere Hodgson.
Mertensia ovum, also known as the Arctic comb jelly or sea nut, is a cydippid comb jelly or ctenophore first described as Beroe ovum by Johan Christian Fabricius in 1780. It is the only species in the genus Mertensia. Unusually among ctenophores, which normally prefer warmer waters, it is found in the Arctic and adjacent polar seas, mostly in surface waters down to 50 metres (160 ft).
Collinia is a genus of parasitoid ciliates of the Colliniidae family.
Collinia beringensis is a species of parasitoid ciliates of the Colliniidae family. It is an endoparasite of Thysanoessa inermis, a species of krill.
Benthosema glaciale, or glacier lantern fish, is the most common species of lanternfish and important part of the midwater ecosystem of northern North Atlantic.
Themisto libellula is a marine amphipod of the family Hyperiidae. The species lives for 2 to 3 years, and grows up to 60 millimetres (2.4 in) over its lifetime. They are found in large quantities in Arctic water.
Ann Bucklin is Professor Emeritus of Marine Sciences at the University of Connecticut known for her work using molecular tools to study zooplankton. Bucklin was elected a fellow of the American Association for the Advancement of Science in 1995.
A micronekton is a group of organisms of 2 to 20 cm in size which are able to swim independently of ocean currents. The word 'nekton' is derived from the Greek νήκτον, translit. nekton, meaning "to swim", and was coined by Ernst Haeckel in 1890.