Thysanoessa is a genus of the

krill Krill ''(Euphausiids)'' (: krill) are small and exclusively marine crustaceans of the order (biology), order Euphausiacea, found in all of the world's oceans. The name "krill" comes from the Norwegian language, Norwegian word ', meaning "small ...

that play critical roles in the marine food web. They're abundant in Arctic and Antarctic areas, feeding on

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

and

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

to obtain energy. 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.

Growth & development

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. 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. 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. As the body expands, the cephalothorax becomes transparent.

Anatomy

Thysanoessa are

decapod crustaceans The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfish, shrimp, and pr ...

, meaning that they have five pairs of legs on their three-parted body. The

cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

is divided into the head, the thorax, and the

pleon The anatomy of a decapod consists of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment – often called a somite – may possess one pair of appendages, although in various groups these ma ...

. 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
setae
The Thysanoessa genus is a

bioluminescent Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...

organism. They have organs called

photophore A photophore is a specialized anatomical structure found in a variety of organisms that emits light through the process of boluminescence. This light may be produced endogenously by the organism itself (symbiotic) or generated through a mut ...

s that undergo an enzymatic chemical reaction. These bioluminescent enzymes derive from the consumption of

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

s, yet the complete role of photophores are still unknown.

Feeding

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. Thysanoessa have a high content of fatty acid that comes from the consumption of

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s 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.

Habitat

Thysanoessa are found in the Western and Central Barents Sea. Their location varies within species, while some ar
boreal
others live in a sub-arctic habitat. Shifts in locations are caused by impacts of global warming and severe changes in ocean temperatures. Given this, Arctic habitats are projected to shift vigorously in the next years, impacting krill growth and abundance of nutrients such as

chlorophyll a } Chlorophyll ''a'' is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light, and it is a poor absorber of green and near-green portions of the spectrum. Chlorop ...

. 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.

Species

''Thysanoessa'' is a genus of

, containing the following species: *''

Thysanoessa gregaria Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' G. O. Sars, 1885 *'' Thysanoessa inermis'' ( Krøyer, 1846)

*''

Thysanoessa inspinata Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' Nemoto, 1963 *''

Thysanoessa longicaudata Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' (Krøyer, 1846) *''

Thysanoessa longipes Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' Brandt, 1851 Thysanoessa longipes

*''

Thysanoessa macrura Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' G. O. Sars, 1885 *''

Thysanoessa parva Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' Hansen, 1905 *''

Thysanoessa raschii ''Thysanoessa raschii'', sometimes known as Arctic krill, is one of the most common krill, euphausiid species of the subarctic and Arctic Ocean, Arctic seas. They may reach long, and are sexual maturity, sexually mature above . ''T. raschii'' ...

'' ( M. Sars, 1864) *''

Thysanoessa spinifera Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' Holmes, 1900 *''

Thysanoessa vicina Thysanoessa is a genus of the krill 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. Thysanoessa are responsible for the transportation of carbo ...

'' Hansen, 1911

References

# "''Thysanoessa'' Brandt, 1851".

Integrated Taxonomic Information System The Integrated Taxonomic Information System (ITIS) is an American partnership of federal agencies designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagenc ...

. Retrieved June 19, 2011. # Agersted, Mette Dalgaard; Nielsen, Torkel Gissel; Munk, Peter; Vismann, Bent; Arendt, Kristine Engel (2011-06-01). "The functional biology and trophic role of krill (Thysanoessa raschii) in a Greenlandic fjord". ''Marine Biology''. 158 (6): 1387–1402. doi:10.1007/s00227-011-1657-z.

ISSN An International Standard Serial Number (ISSN) is an eight-digit to uniquely identify a periodical publication (periodical), such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...

1432-1793. # P, Dalpadado; Hr, Skjoldal (1996-12-05). "Abundance, maturity and growth of the krill species Thysanoessa inermis and T. longicaudata in the Barents Sea". ''Marine Ecology Progress Series''. 144: 175–183. doi:10.3354/meps144175.

0171-8630. # "Antarctic Krill". ''Oceana''. Retrieved 2022-04-12. # "Marine Species Identification Portal : Thysanoessa inermis". ''species-identification.org''. Retrieved 2022-04-13. # "Thysanoessa - an overview , ScienceDirect Topics". ''www.sciencedirect.com''. Retrieved 2022-04-12. # Taki, K. (2010-12-17). "Distribution and population structure of Thysanoessa inspinata and its dominance among euphausiids off northeastern Japan". ''Journal of Plankton Research''. 33 (6): 891–906. doi:10.1093/plankt/fbq162.

0142-7873. # Harvey, H. Rodger; Pleuthner, Rachel L.; Lessard, Evelyn J.; Bernhardt, Megan J.; Tracy Shaw, C. (2012-06-15). "Physical and biochemical properties of the euphausiids Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes in the eastern Bering Sea". # Piñones, Andrea; Fedorov, Alexey V. (2016-08-16). "Projected changes of Antarctic krill habitat by the end of the 21st century". ''Geophysical Research Letters''. 43 (16): 8580–8589. doi:10.1002/2016gl069656.

0094-8276.

External links

* {{Taxonbar, from=Q687855 Krill Crustacean genera Taxa named by Johann Friedrich von Brandt