#Euphausiacea

[taxonomytournament]

Taxonomy Tournament: Crustaceans

Euphausiacea. This order is made up of krill, small marine crustaceans. Most species form large swarms, and they are important for the marine food chain.

Isopoda. This order is made up of isopods, including terrestrial species like the potato bug and aquatic species like the giant isopod. Some eat dead matter, others are filter feeders, and some are parasites, mostly of fish.

[bestanimal]

Round 2 - Arthropoda - Malacostraca

(Sources - 1, 2, 3, 4)

Malacostraca is the second largest class of crustaceans, and what most people picture when they hear the word crustacean! It contains over 40,000 species separated into 17 orders: Leptostraca, Stomatopoda (“Mantis Shrimp”), Decapoda (“Crabs”, “Lobsters”, “Crayfish”, “Shrimp”, and “Prawns”), Euphausiacea (“Krill”), Thermosbaenacea, Mysida (“Opossum Shrimp”), Stygiomysida, Lophogastrida, Spelaeogriphacea, Mictacea, Bochusacea, Cumacea (“Hooded/Comma Shrimp”), Tanaidacea, Amphipoda, Isopoda, Anaspidacea, and Bathynellacea. Many are scavengers, some are predators, some are herbivores, some are filter feeders, and some are parasites.

Malacostracans live worldwide, in marine, freshwater, and terrestrial environments, and have a large diversity of body forms. They are united by their segmentation of 20-21 body segments divided into a 5-segmented head, an 8-segmented thorax, and a 6-segmented abdomen with a telson, except in Leptostraca which has 7 abdominal segments. They have a pair of jointed appendages on each abdominal segment, though some groups have lost them secondarily. In some, three thoracic segments may be fused with the head to form a cephalothorax, the associated legs becoming maxillipeds. They have two pairs of antennae, which often branch into two parts. Their mouthparts have a pair of mandibles, maxillules, and maxillae. Many taxa have compound eyes on moveable stalks. Some have a carapace which covers the head, part or all of the thorax and some of the abdomen. The carapace may be fused with some of the thoraacic segments or hinged with two parts. This is one of the most diverse classes in the animal kingdom, and their anatomy and behavior would be hard to summarize further in just one paragraph!

The oldest malacostracans are the Leptostracans, which first appeared as fossils from the Cambrian period.

Propaganda under the cut:

“Carcinisation” has become a meme meaning “everything becomes crab”, but it actually only refers to the phenomenon of decapods convergently evolving crab-like anatomy. The Infraorder Brachyura contains the “True Crabs”, but at least 5 groups of unrelated decapods have evolved similar anatomy: a flat and broad cephalothorax.

Stomatopods (“Mantis Shrimp”) are known for their excellent color vision, but they probably can not actually see “shrimp colors.” They can see ultraviolet and polarized light, but their excess of photoreceptor cells actually lets them process their environment faster than we can, rather than differentiate between a multitude of different colors. This allows them to have quick reaction times, either to escape predators, fight or flee from rivals, or strike at their prey with amazing speed.

Malacostraca contains the largest living arthropods: the Japanese Spider Crab (Macrocheira kaempferi) with a legspan of up to 4 metres (13 ft) long, and the American Lobster (Homarus americanus), which can get up to 20 kilograms (44 lb).

Many species of malacostracans are commonly kept as pets, including crabs, crayfish, shrimp, mantis shrimp, and isopods.

Cute creb eat a cherry:

[aropride]

i'm going to become a marine crustacean of the order euphausiacea

[tussive]

I don't want to be hungry on someone's post so I'm making my own but that post about krill makes me think krill would be delicious.

Also found this.

[lycansprites]

im going to krill myself. becomes 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

[nyudpicgimaging]

Helen Ma, Condensed Blue Whale

This Project, Condensed Blue Whale, is inspired by the Chinese song Condensed Blue Whale (浓缩蓝鲸) by the artist Qiu De (裘德). It talks about a story that takes place in the year 3000, where a scientist condensed the soul of a gigantic Blue Whale inside the body of an extremely small Euphausiacea, which is a kind of half-transparent shrimp. The small body of shrimp now has the experience of roaming in the deep ocean, but the vast blue whale begins to be skeptical about the question of whether its soul is as tiny as the body it owns at this moment. It is supposed to be a romantic story that questions the philosophical essence of “who I am” – the body, the mind, or the combination of both. However, it is somehow cruel as well. 

Inspired by Sabrina Ratte and her Muse, Donna J. Haraway, I started to consider the idea of the Cyborg (a combination of organism and machine) and the value of the community that everything is mixed in society, without clear binary distinctions. 

When we are observing animals, are animals observing us as well? When society develops to be that high technology and human beings are getting very used to being adapted to living together with those techniques that we are not necessarily able to control, what will be human beings’ future? When we do all kinds of experiments on animals, we might also gradually become some kind of experimental object to some unknowns. Instead of the utopic idea given by Haraway, this project shows my dystopian perspective on the future community. 

[ricmlm]

Krill - The Basics of Life!🧬😉 COMMON NAME: Krill SCIENTIFIC NAME: Euphausiacea TYPE: Invertebrates DIET: Herbivore GROUP NAME: Swarm SIZE: 2.4 inches WEIGHT: 0.035 ounces SIZE RELATIVE TO A PAPER CLIP: View on Pic. The lowly krill averages only about two inches in length, but it represents a giant-sized link in the global food chain. These small, shrimp-like crustaceans are essentially the fuel that runs the engine of the Earth’s marine ecosystems. Role in the Food Chain Krill feed on phytoplankton, microscopic, single-celled plants that drift near the ocean’s surface and live off carbon dioxide and the sun’s rays. They in turn are the main staple in the diets of literally hundreds of different animals, from fish, to birds, to baleen whales. https://www.instagram.com/p/CpYbqI4jGHw/?igshid=NGJjMDIxMWI=

[silphilis]

call me euphausiacea the way im trying to be sucked in whole by a girl with a maximum confirmed length of 29.9 meters

what if i krilled myself

[elementalgod-aj]

Animal practice 33

Panarthropoda

Arthropoda 3

Crustacean 2

Brachyura

Cyrus (Ghost crab/Christmas island crab)

Anomura

Hikikomori (secondary crabs)

Astacidea

Shelton (lobster)

Etta ( Crayfish)

Gebiidea/Axiidea

Clay (Mud Lobster)

Achelata

Prong (Spiny/Slipper lobster)

Caridea

Parker (Shrimp)

Stenopodidea

Ringster (Boxing shrimp)

Dendrobranchiata

Trawl (Tiger prawn)

Euphausiacea

Minute (Krill)

[f107group1]

Let’s KRILL this love!

Did you know that Antarctic Krill can glow in the dark (like a lightstick *0*)?

They are bioluminescent! That means krill swarms look like a KPOP ocean!

Classification

Kingdom: Animalia

     Subkingdom: Bilateria

            Infrakingdom: Protostomia

                 Superphylum: Ecdysozoa

                       Phylum: Arthropoda

                            Class: Malacostraca

                                  Subclass: Eumalacostraca

                                        Order: Euphausiacea

                                              Family: Euphausiidae

                                                    Genus: Euphausia

                                                           Species: Euphausia superba

(ITIS, n.d.)

Distribution and habitat

Figure 1. Geographical Distribution of Antarctic krill (fao.org, n,d,)

E. superba inhabits a wide circumpolar belt between the Antarctic Continental Shelf break and the Antarctic Polar Frontal Zone. Antarctic krill live in open marine waters (fao.org, n.d.). The larvae of the krill begin near the seafloor and gradually ascend towards the surface as it develops. Adult krills are found at depths ranging from surface waters to depths of 350 m and have occasionally been found as deep as 600 m. They usually dwell in deeper waters during the winter season (Gierak, n.d.).

Anatomy

Figure 2. External Anatomy of Antarctic Krill

E. superba known as Antarctic krills are shrimp-like in appearance though they can easily be distinguished from shrimp by their visible gills. Just like any other decapods they have exoskeleton which are made of chitin and have three body parts which is the cephalothorax, pleon and the telson. The cephalothorax bears the antennae, compound eye, 6 filter legs which are also called thoracopods and the gills. Krills have compound eyes which aid them in seeing while their antennae serve as another sensory organ as they live in the deep. The thoracopods or the filter legs on the other hand, assists the krill in straining its food from the water. Although the gills, guts and gastric mill are not part of its external anatomy, the three are visible from the outside. The middle part of its body is the pleon where the pleopods and the photophores are located. There are 5 pairs of pleopods or swimming legs that allow them to swim in the water column while the photophores or light organs act as a defense mechanism or a signal for their mates. Lastly, is the telson  which is used by decapods as a paddle in caridoid escape reactions through backward propulsion (Grzimek's Student Animal Life Resource, n.d.).

Life Cycle

Figure 3. Life Cycle of an Antarctic Krills Krills reproduce sexually and it usually happens when food is abundant. The male krill produces sperm packets and uses its first pair of pleopods called petasma to transfer the sperm into the thelycum of the female. They store the sperm until they are ready to lay their eggs. These eggs are fertilized once they are released by the female. These eggs settle at the seafloor and gastrulation happens. Eventually, the eggs will hatch and become a nauplius. In this the nauplius has only one eye and is not segmented yet. Then, the nauplius will molt and become a metanauplius wherein limb development begins and it will start to migrate to the surface which is known as developmental ascent. As it molts and grows, it becomes a calyptopis and eventually a furcilia wherein the movable compound eyes start to project at the edge of its carapace. The furcilia develops into a juvenile which can grow from 4 to 10 mm long (Gierak, 2013).

Ecology

Figure 4.  Thoracic endopodite of krill (wikipedia.org, n.d.)

Antarctic krill are filter-feeders that feed mainly on phytoplankton. They exhibit diurnal vertical migration, which means that they rise to the surface at night to feed by using their small, hair-like legs specifically thoracic endopodites as a suspension feeding basket. Apart from phytoplankton, they also eat copepods, zooplankton, and other krill or molted exoskeletons. In the winter, they eat algae under the surface of sea ice. They are considered the dominant herbivore of the Southern Ocean. Its biomass in the Antarctic Ocean is estimated to be between 125 mmt and 750 mmt, the largest biomass of any species on earth (Hardy, 2008). Antarctic krill is the keystone species of the entire Antarctic food chain. They provide a vital food source for whales, seals, squids, penguins, fishes, albatrosses, and many other species of birds. To avoid predation, they exhibit schooling behavior or swarming. Moreover, krill may be parasitized by organisms like protozoans, particularly the genus Ephelota. This suctorian ciliates interacting with E. superba cause hydrodynamic drag on krill swimming and make the host more vulnerable to visual predators (Gómez-Gutiérrez & Morales-Ávila, 2016). Other parasitic species include Cephaloidophora pacifica and Apostoma sp. 

UNLI-KRILL @ 199!

Krill’s POV 

Relationship with humans

Figure 5.  Sports Research’s Antarctic Krill Oil with SUPERBA 2 (ph.iherb.com, n.d.)

Figure 6.  Krill/shrimp chili paste and dipping assortments in Thailand (quora.com, 2016)

Although krill is mainly used as aquaculture feed and bait for fishing, it is also processed into a variety of products for human consumption such as paste, frozen tails, sticks, etc. Krill products have been known to pharmaceutical and industrial industries since it is found that the krill's lipid content can be used as a nutritional source of fatty acids that is potential in lowering cholesterol levels. Studies found that the lipids of Antarctic krill are more stable than those of some fishes consumed by humans. Krill digestive proteases can also be injected into humans to reduce pressure on nerve roots between vertebral discs (Gierak, n.d.). Tou et al. describe Antarctic krill as a “rich source of high-quality protein” with low fat and high levels of Omega-3s and antioxidants and the main source of the renowned krill oil.

5 health benefits of Krill oil you shouldn’t miss!

Little did you know that..

They are age-defying! 

*jaw-dropping moment because olay age-defying serum just cant--*

➔ They have the ability to shrink in size when starve to conserve energy during the winter. Thus, scientists can’t tell the age of a krill solely from its size. 

Phytoplankton is just a summer fling! 

➔ They can survive more than 200 days without food.

Krillions of krills!

➔ Krill swarm together in massive numbers, with as many as 30,000 in one cubic meter of a krill swarm.

A Little Giant! 

➔ It’s estimated that the total weight of Antarctic krill is more than the weight of all humans on Earth (Usoceangov, 2015). 

Food is life but swimming is lifer! 

➔ They are heavier than seawater and must swim constantly to stay afloat.

Climate heroes!

➔ Tarling and Thorpe (2017) have discovered that krill play a crucial role in sequestering carbon. 

References:

Clark, D. (2012, September 17). The anatomy of the Arctic krill [Digital image]. Retrieved November 12, 2020, from http://1.bp.blogspot.com/-7NY88MHBVpc/UFfn-sAknuI/AAAAAAAAAW4/nkt1_Ba8G8k/s1600/Antarctic_krill_anatomy.jpg

Euphausia superba. (n.d.). ITIS. Retrieved November 8, 2020, from https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=95514#null

Euphausia superba (Dana, 1852). (n.d.). FAO. Retrieved November 10, 2020, from http://www.fao.org/fishery/species/3393/en

Exuvia of Antarctic krill [Online image]. (2005). English Wikipedia. https://commons.wikimedia.org/wiki/File:Exuviakrillkils.jpg

Gierak, R. (2013).  Euphausia superba (Antarctic krill). Retrieved November 12, 2020, from https://animaldiversity.org/accounts/Euphausia_superba/

Gómez-Gutiérrez, J., & Morales-Ávila, J. R. (2016). Parasites and Diseases. Biology and Ecology of Antarctic Krill, 351–386. https://doi.org/10.1007/978-3-319-29279-3_10

Grzimek's Animal Life Encyclopedia. (2020). Krill: Euphausiacea. Retrieved November 12, 2020, from https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/krill-euphausiacea

Hardy, R. W. (2008). Alternative marine sources of fish feed and farmed fish quality. Improving Farmed Fish Quality and Safety, 328–342. https://doi.org/10.1533/9781845694920.2.328

Naruturd_505. (n.d.). Hoshiumi Korai A Little Giant GIF [Online GIF]. https://tenor.com/view/hoshiumi-korai-alittle-giant-smile-haikyuu-anime-gif-17909731

Oh, yeah- what?! GIF. (2013). Gfycat. https://gfycat.com/detailedfaintalbertosaurus

SuperSmiles17. (2013). Definitely one in a Krillion! [Online GIF]. https://imgur.com/gallery/YtN30/comment/16282449

Tarling, G.A., and Thorpe, S.E. (2017). Oceanic swarms of Antarctic krill perform satiation sinking. Proc. R. Soc. B., 28420172015. http://doi.org/10.1098/rspb.2017.2015

The Ozone Hole. (n.d.). [Life Cycle of Antarctic Krill]. Retrieved November 12, 2020, from http://www.theozonehole.org/images/v43n2-wiebe3en_10243.jpg

[Untitled image of a tardigrade]. (2017). BBC. https://www.bbc.com/news/science-environment-40752669

Usoceangov. (2015). Animals of the Ice - Antarctic Krill. Youtube. Retrieved November 10, 2020, from https://www.youtube.com/watch?v=RFqhocQqbgM

[climatechangers]

Advantages vs Disadvantages

Although the cons outweigh the pros in regards to Climate Change, there are still various advantages that directly contribute to Earth.

ADVANTAGES

 The Arctic, Antarctic, Siberia, and other frozen regions of the earth might experience more plant growth and milder climates.

The next ice age could possibly be prevented

The Northwest Passage through the formerly icy Canadian Arctic Archipelago could arguably open up to transportation.

Fewer deaths or injuries would occur due to arctic conditions.

Longer growing seasons could mean increased agricultural production in some areas.

DISADVANTAGES

Changes in ocean circulation and the resulting warmer temperatures disrupt the world’s normal weather patterns, bringing about more extreme weather and an increased frequency of severe and catastrophic storms, such as typhoons and hurricanes.

Higher sea levels lead to flooding of the lowlands. Islands and coastlines are engulfed by water leading to death and disease due to flooding.

The acidification of warming oceans leads to a loss of coral reefs. Coral reefs protect shorelines from heavy waves, storms, and floods and while they only cover about 1 percent of the ocean floor, reefs provide a habitat for 25 percent of ocean species. Demolished reefs lead to increased erosion and coastal property damage and the extinction of species.

Warming ocean waters mean increased melting of glaciers and ice sheets. Smaller ice sheets form each subsequent winter, which has a devastating impact on the habitat of cold-climate animals and the Earth’s reserves of freshwater.

Less sea ice, warmer water, and increased acidity are catastrophic for krill which forms the base of the ocean's food web and feeds whales, seals, fish, and penguins. Emperor penguin colonies are also expected to decline due to the loss of sea ice and rising temperatures.

Word Bank:

Coral reefs- An underwater ecosystem characterized by reef-building corals

Glaciers- a slowly moving mass or river of ice

Ice sheets- a permanent layer of ice covering an extensive tract of land

Krill- any small shrimplike marine crustacean of the order Euphausiacea

Sources:

Is there any upside in Global Warming? Matt Rosenberg. July 11, 2019.

[soclaimon]

Rayong beach comes alive with krill fishing #SootinClaimon.Com

#SootinClaimon.Com : ขอบคุณแหล่งข้อมูล : หนังสือพิมพ์ The Nation. https://www.nationthailand.com/in-focus/40006489 Rayong’s Suan Son Beach is bustling with fishermen catching krill, much to the excitement of tourists. Krill (Euphausiacea) has doubled in price from 2020 as its popularity increases. It is used to cook various types of delicious dishes, including high-quality shrimp paste. On…

[naturfactory]

KRILL OIL GOLD EDITION 60 PERLAS - SCIENTIFFIC NUTRITION Krill Oil Gold Edition de Scientiffic Nutrition es un producto compuesto por aceite de krill antártico.  El Krill es el nombre por el que se conocen genéricamente a los eufusiáceos (Euphausiacea) que son un tipo de crustáceo que se alimenta de fitoplancton. El aceite derivado de Krill es rico en ácidos grasos esenciales Omega 3 y 6.  EL aceite de krill es muy estable y libre de metales pesados, de hecho se considera más eficiente que cualquier aceite de pescado. El aceite de Krill tiene la capacidad de mejorar el dolor articular, siendo muy útil en procesos inflamatorios.  Principales beneficios Krill Oil Gold Edition de Scientiffic Nutrition: Fuente de ácidos grasos esenciales Omega 3 y Omega 6. Mejor absorción que el aceite de pescado. Rico en ácido eicosapentaenoico y ácido docosahexagenoico (EPA/DHA) que contribuyen a la función normal del corazón. El ácido docosahexaenoico (DHA) contribuye al mantenimiento de la función normal del cerebro y el mantenimiento de la visión normal. Ayuda a regular los índices de colesterol y triglicéridos, además de tener propiedades antioxidantes. El aceite de Krill tiene mejor biodisponibilidad y absorción que el aceite de pescado, siendo también más estable y resistente a la oxidación que este último. Krill Oil te ofrece una potente dosis de aceite de Krill purificado fácil de asimilar en cada cápsula blanda de gelatina. Presentación: Envase de 60 perlas. Modo de empleo: Tome 2 cápsulas al día con un gran vaso de agua. https://www.naturfactory.com/acidos-grasos/omega-369/krill-oil-gold-edition-60-perlas-scientiffic-nutrition.html 19,90 €

[jmoscad]

EL ATÚN ROJO. ALGUNAS CARACTERÍSTICAS. Libro CIMARRÓN José L. Cort) 1ªpart: El atún rojo,Thunnus thynnus (L.), del Atlántico y Mediterráneo pertenece a la familia de los peces escómbridos (Scombridae).Puede llegar a pesar 725 kg, alcanzar una longitud de 3,3 m y vivir más de treinta años. El registro oficial del mayor atún rojo es de 679 kg, un pez capturado en aguas de Nueva Escocia (Canadá) en 1979, siendo el actual récord Guinness. Forma grandes cardúmenes y se alimenta principalmente de otros peces, cefalópodos, pequeños crustáceos como el krill (Euphausiacea) y cangrejos pelágicos. Su forma es altamente hidrodinámica ya que está totalmente adaptado a la movilidad.Habita en aguas templadas del Atlántico Norte y el mar Mediterráneo (hasta el mar Negro). En la parte oriental del océano Atlántico se encuentra desde Senegal y Cabo Verde (15 N) hasta cerca del Círculo Polar Ártico (75º N), donde se registran temperaturas de 5ºC.En la parte occidental, desde Brasil hasta Terranova. También se ha localizado en el Atlántico sur. Su torrente sanguíneo forma el núcleo de un sistema de intercambio de calor altamente evolucionado, por lo que su temperatura interna puede mantenerse hasta 21°C más alta que la del agua que lo rodea, siendo ésta una de las razones de su amplia distribución en el océano. El atún rojo puede aparecer en las cálidas aguas de las Bahamas a cerca de 30°C y 50 días después en aguas noruegas, donde el agua apenas alcanza los10° C. •••Las migraciones del atún rojo dependen de la edad y la longitud de los peces y están relacionadas principalmente con el desove y la búsqueda de alimento.Las migraciones de peces adultos (>40 kg) hacia las zonas de desove en el Mediterráneo y su regreso al océano para alimentarse se conocen desde hace milenios.Sus migraciones se hacen cada vez mayores a medida que aumentan su tamaño. •••Para realizar la reproducción los atunes rojos emigran formando grandes bancos que eligen las áreas más apropiadas en función de numerosas variables ecológicas y ambientales. En general, las migraciones de este pez, tanto en adultos como juveniles (<40 kg), parecen estar asociadas a los grandes sistemas de corrientes oceánicas. (en Almansa) https://www.instagram.com/p/B_IOZuYKgfQ/?igshid=1wv5zrbfj7xbd

[curiositti]

Tetra Betta 100 ml / 27 g Forro de alta calidad forro diseñado para satinado, Splendens (Betta principal) de pescado y otros peces laberinto: enthaelt un porcentaje de proteínas por adición de camarón apropiada y Euphausiacea proteínas animales foerdern el crecimiento y la auspraegung de aletas con natuerlichen farbverstaerkern Composición: Pescado y subproductos de pescado, cereales, vegetales eiweis extractos, levaduras, suave de animales y el cáncer (Arte Mia salina 3,3%, gefriergetr kleink liofilizados rebse (Euphasia Pacifica) 3,3%), desechos y Grasas, azúcar, algas, minerales.

[reseau-actu]

À l’heure actuelle, les océans terrestres et leurs profondeurs sont moins bien connus que le Système solaire lui-même. Une grande partie de la faune et de la flore de ces environnements reste encore à découvrir, et certains phénomènes affectant la faune sous-marine sont encore mal compris par les scientifiques. C’est notamment le cas du gigantisme abyssal, selon lequel les crustacés, invertébrés et autres animaux des profondeurs possèdent une taille bien plus grande que ceux de la même espèce vivant en surface.

Dans les profondeurs océaniques, un curieux phénomène affecte les animaux : leur taille semble démesurée comparée à celle de leurs homologues de surface. Un phénomène biologique que les scientifiques commencent déjà à étudier dans les années 1880, notamment avec les travaux du naturaliste britannique Henry Nottidge Moseley concernant les Pycnogonida, une classe d’arthropodes regroupant les araignées de mer.

Par suite, le biologiste suisse Jean Louis Rodolphe Agassiz décrira la taille spectaculaire d’un isopode bien connue des biologistes marins : Bathynomus giganteus, un isopode géant et un exemple notable de gigantisme abyssal. Plus de 120 ans après les premiers rapports mettant en évidence le phénomène, ce dernier n’a toujours pas d’explication définitive. Cependant, les biologistes ont tout de même proposé certaines hypothèses.

Dès le 19ème siècle, les biologistes décrivent Bathynomus giganteus, ou Bathynome géant, un isopode géant représentatif du phénomène de gigantisme abyssal. Crédits : NOAA

L’hypothèse majoritaire est une application de la règle écogéographique de Bergmann. Cette règle veut que qu’au sein d’un même clade, la masse des populations d’animaux endothermes est directement corrélée à la température de l’environnement. Ainsi, les animaux vivant dans un environnement froid posséderont une taille et une masse plus importantes que leurs homologues évoluant dans des environnements plus chauds.

Cette règle s’explique par le fait que les animaux possédant une grande taille disposent d’un rapport surface/volume du corps plus petit, et donc irradient moins de chaleur corporelle. La taille et la masse jouent ainsi un rôle important dans la thermorégulation. Les biologistes pensent ainsi que cette règle s’applique de la même manière aux crustacés et autres invertébrés marins. Une température plus basse entraîne des cellules plus grandes et une espérance de vie plus élevée selon les scientifiques.

Photo d’un isopode géant au milieu de crevettes. La taille de ce crustacé est bien plus grande que celle de ses homologues de la surface. Crédits : Laika AC

Cette tendance d’augmentation des proportions corporelles en fonction de la profondeur a été observée chez des nombreux ordres : Amphipoda, Decapoda, Euphausiacea, Isopoda ou encore Mysida. Cependant, la température ne semble pas jouer un rôle pour toutes les espèces d’animaux vivant en profondeur. Par exemple, les vers tubicoles géants vivant près des cheminées hydrothermales, comme Riftia pachyptila, arborent une taille similaire à celle des vers tubicoles Lamellibrachia luymesi, vivant dans les zones froides des profondeurs.

Sur le même sujet : Un poisson-lune géant et mystérieux a été découvert, échoué en Californie

D’autres facteurs ont été proposés, en complément ou non de l’hypothèse du gradient de température. Ainsi, la raréfaction des ressources et des prédateurs, la faible densité des populations animales et un apport nutritionnel faible mais constant, ont été avancés. La pression hydrostatique élevée est également une hypothèse, mais tend à être mise à mal par des observations effectuées en Arctique et en Antarctique.

Avec des proportions pouvant atteindre 3.5 m d’envergure et une masse de 20 kg, l’araignée-crabe géante du Japon est le plus grand arthropode vivant. Crédits : Malton Heckart

De nombreux exemples d’animaux mettant en évidence le phénomène de gigantisme abyssal existent. Alicella gigantea, un crustacé amphipode géant des profondeurs atteint en moyenne 34 cm, contre 3 cm maximum pour ses homologues de la surface. Bathynomus giganteus, ou Bathynome géant, est un isopode marin pouvant atteindre 50 cm et 1.7 kg, en faisant le plus grand des isopodes. Macrocheira kaempferi, ou crabe-araignée géant du Japon, peut atteindre 3.5 m d’envergure et 20 kg, c’est le plus grand des arthropodes vivant.

Avec une taille pouvant atteindre 12 mètres de long, le régalec (Regalecus glesne) est le plus grand poisson osseux connu à ce jour. Crédits : Jean-Christophe Cane

Dans les autres invertébrés, de très nombreuses espèces de calmar sont des exemples de gigantisme abyssal. Le calmar colossal, Mesonychoteuthis hamiltoni, peut atteindre 14 m et 500 kg ; les calmars géants (Architeuthis dux) peuvent atteindre 13 m et 275 kg.

Mais le titre du plus grand octopode vivant est détenu par Haliphron atlanticus, encore appelée pieuvre à sept bras, avec une taille maximale de 4 m et une masse de 75 kg. Quant aux vertébrés, le régalec (Regalecus glesne), avec une taille de 12 m, est le plus long poisson osseux connu.

Cet article Animaux géants des profondeurs : qu’est-ce que le gigantisme abyssal ? est apparu en premier sur Trust My Science.

Thomas Boisson

Source: Trust My Science