Euprymna scolopes develops rapidly and grows exponentially. After copulation, there is a 18-26 day embryonic period. The planktonic hatchling first emerges from the egg, and is initially aposymbiotic, meaning it cannot use its light organ. After several days, the hatchling develops into a planktonic paralarva that can partially make use of the light organ. The paralarva develops into a juvenile after ten days, and becomes mature enough to travel into shallower waters. After 130 days, when the squid is a subadult, the light organ fully functions for hunting and camouflage. The squid will have little to no further growth after 180 days. Male and female organisms, which occur in equal numbers, reach sexual maturation 60 days after hatching. Temperature may be a factor in the time to reach full sexual maturity. Interaction with Vibrio fischeri is not required for normal development and growth.
Development - Life Cycle: metamorphosis
As previously mentioned, Euprymna scolopes uses counterillumination to camouflage from predators. Another defense mechanism is burying itself in an outer covering made of sand. Last, the squid releases an amount of ink when they sense a stimuli indicating the presence of a predator. The pool of ink is used to deceive the predator and prevent attack by resembling the shape of the squid. Known predators of E. scolopes include lizardfish (family Synodontidae), barracuda (genus Sphyraena), and Hawaiian monk seal (Monachus schauinslandi).
Known Predators:
Anti-predator Adaptations: cryptic
Euprymna scolopes is one of the smallest and slimmest sepiolid squids. The mantle plus tentacles measure an average of 35 mm (1.4 in) in length, and weighs an average of 2.76 grams (0.09 oz). The birth mass of a hatchling is an average 0.005 grams (0.00018 oz). Males have slightly larger suckers than females, with thinner posterior mantles. Both sexes have a pair of unique paddle shaped fins that aid in swimming. A feature unique to Euprymna scolopes is the bilobed and bioluminescent light organ present inside the squid’s mantle cavity. This organ, which functions through its interaction with its symbiotic partner Vibrio fischeri, provides light, allowing the squid to hunt its prey at night. This squid also possesses metabracial vesicles, which function as the eyes of this bobtail squid. The vesicles allow the squid to perceive and manipulate the amount of light it can give off, so the squid can camouflage itself in a process known as counterillumination.
Range length: 20 to 30 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently
Euprymna scolopes has a lifespan that averages 2-3 months in the wild and 3-5 months in captivity.
Typical lifespan
Status: wild: 2 to 3 months.
Typical lifespan
Status: captivity: 3 to 5 months.
Euprymna scolopes is found in warm, shallow coastal waters 2-4 cm deep. This is unusual because most sepiolid squids reside in very deep water. Euprymna scolopes is often seen laying its eggs on the foundations of coral ridges. During the day, these squid are buried in the sand. At night, they emerge and wade through the sand with their bioluminescent light organ which allows them to see and hunt in the dark.
Habitat Regions: tropical ; saltwater or marine
Aquatic Biomes: benthic ; coastal
Euprymna scolopes is a sepiolid squid endemic to the oceanic habitats surrounding the Hawaiian Islands. This squid can greatly affect the relative abundance and geographic distribution of its bacterial symbiont Vibrio fischeri.
Biogeographic Regions: pacific ocean (Native )
The primary component of the adult E. scolopes diet is mysid shrimp, and younger squids will also consume crustaceans in the genus Artemia. Euprymna scolopes is a cryptic "sit and wait" predator. The squid buries itself in the sand with its tentacles and wait for prey to pass by. Euprymna scolopes attacks by aiming all the arms at the prey and strikes using the two tentacles. If the squid misses the prey it remains buried and waits for another organism.
Animal Foods: aquatic crustaceans
Primary Diet: carnivore (Eats non-insect arthropods)
Euprymna scolopes has a mutualistic relationship with the marine bacteria Vibrio fischeri, making the squid bioluminescent.
Although they are inhabitants of areas near coral reefs, there is no evidence to suggest Euprymna scolopes has an effect or relationship on the maintenance of the community around the reef.
Mutualist Species:
There is no information indicating any positive effects by Euprymna scolopes on humans.
There are no known negative effects of Euprymna scolopes on humans.
Euprymna scolopes is classified by IUCN as Data Deficient because of the uncertain status of its taxonomy (genus and species).
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Euprymna scolopes has a symbiotic relationship with a bioluminescent marine bacterium called Vibrio fischeri. This mutualistic relationship begins early in the life stages of the squid and development of the light organ results. The squid controls the amount and timing of the bioluminescence given off by the bacteria. When the bacteria are found outside of this mutualistic relationship the strength of the light given off is not nearly as strong as it is when it is housed inside the light organ of E. scolopes. This light organ is generally used for a specialized behavior known as counterillumination, which allows the organism to camouflage themselves and avoid predators.
Communication Channels: tactile ; chemical
Other Communication Modes: photic/bioluminescent
Perception Channels: polarized light ; tactile ; chemical
There is no information on the mating system of Euprymna scolopes.
Mating is initiated by the male, which grabs the female and places its spermatophore in the female's mantle. The female's mantle will become larger as it is filled with eggs. Mating lasts 30-50 minutes, and occurs mostly at night. Studies have shown that rainfall increases the amount of breeding. There are no specific seasonal breeding intervals for this squid. Females tend to lay eggs in the morning in shallow areas on coral ridges. Clutch sizes vary between 50-200 eggs. It takes an average 30 minutes to lay each clutch of eggs. The number of clutches each female lays varies greatly. After females are finished laying eggs, they cover them with sand and then depart, leaving the offspring to fend for themselves.
Average number of offspring 100-150
Range number of offspring: 50 to 250.
Average number of offspring: 100-150.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous ; sperm-storing
The female lays clutches of eggs and covers the eggs with sand after which there are no interactions.
Parental Investment: pre-hatching/birth (Protecting: Female)
E. scolopes, similar to other luminous cephalopods emits a polarized light pattern on its surface.This light emitting capability comes from a bacterial population of Vibrio fischeri .Vibrio fischeri is a bioluminescent bacterium which colonizes a special light organ in the squid’s mantle (McFall-Ngai, 2008) which is stored in a special light organ inside the squid’s mantle (Shashar and Hanlon, 1997).The bioluminescent bacterium V. fischeri has developed a mutualistic symbiotic relationship with E. scolopes in which V. fischeri gives the bobtail squid bioluminescence in trade for nutrients (Gillis, 1993).The bobtail squid can survive without its symbiont, and cultures of V. Fischeri are easily grown, making this an excellent model system for studying animal-bacteria symbiotic relationships (McFall-Ngai, 2008).
The bobtail squid’s luminescence is the product of a chemical reaction between V. fischeri and E. scolopes, a defense mechanism by V. fischeri activated to prevent the host from producing too much hydrogen peroxide (Ruby and McFall-Ngai, 1999, Archetti et al., 2011).Hydrogen peroxide, as well as other reactive oxygen species (ROS) such as hypochlorous acid bind otherwise available oxygen and in consequence, reduce growth in the bacterial population (Ruby and McFall-Ngai, 1999).E. scolopes does not retain this bioluminescence while buried during the day; rather it uses it at night for hunting (Shashar and Hanlon, 1997).The bobtail squid turns off its bioluminescence by ejecting 90-95% of its bacterial symbiont at dawn, (Visick and Ruby, 2008) and takes on the shades and colorings of the surrounding sand.The bacteria repopulate inside the squid during the day.At night when E. scolopes becomes predatory, it activates its lustrous colors by feeding its bacterial symbiont oxygen. (Boettcher et al. 1996).
E. Scolopes is a solitary animal unlike its relative the cuttlefish, which interacts with others within a social group.Both male and female E. Scolopes are predators that are active nocturnally.They only interact when mating (Shashar and Hanlon, 1997), and typically avoid other individuals in captivity and in the wild. (Moynihan, 1983). E. Scolopes typically rests beneath a layer of sand during the day. By moving its tentacles in a synchronous sweeping motion, it moves sand over its body until completely buried.This behavior is a simple technique to avoid being preyed upon. This tiny squid also secretes an adhesive from its skin which aids in keeping sand on its body. (Moynihan, 1983)
The carnivorous bobtail squid enters the water column and preys primarily on shrimp and worms at night.Rather than using bioluminescence as a communication tool, the bobtail squid uses this adaptation to avoid casting a shadow. Counterillumination, specifically, allows E. scolopes to imitate the light shed by the moon and stars, become camouflaged, and remain unnoticed by prey or predators (McFall-Ngai, 2008).It sits and waits on the sandy floor for prey to come near and suddenly points all of its tentacles at its target.In a moment, it jets toward its prey and snatches it with its two main arms (Fleisher and Case, 1995).Unlike most other carnivores, the bobtail squid first begins eating its prey from the tail end. (Moynihan, 1983).
The bobtail squid may ink and use jet propulsion as an escape mechanism to confuse predators of its location.They can quickly travel 1 m in this way by jetting, while also changing the patterns on their bodies. (Anderson and Mather, 1996).
The bobtail squid, (Euprymna scolopes) is a small cephalopod that lives in the shallow water off the coast of several of the Hawaiian Islands.The bobtail squid averages 3 cm in length when fully grown (McFall-Ngai, 2008) and its skin is patterned with stripes, blushes, and spots.The squid’s general tone color varies from light tan to dark chocolate and its skin produces a sticky adhesive (Moynihan, 1983).This small carnivore eats tiny fish, shrimp and worms in the water at night, but buries itself in the sand during the day (Moynihan, 1983, Gillis, 1993).The bobtail squid has formed a symbiotic relationship with Vibrio fischeri, a bioluminescent bacterium which colonizes a special light organ in the squid’s mantle (McFall-Ngai, 2008).This small creature uses the light produced by V. fischeri to camouflage from its prey and from predators such as eels, lizard fish (Gillis, 1993) or crabs swimming in the water column (Anderson and Mather, 1996).At dawn, the squid expels 95% of the bacteria from its light organ into the surrounding environment, providing newly hatched juveniles with symbionts and preventing the colony in the host from overpopulating.
The bobtail squid lives in abundant populations off the coast of Hawaii (McFall-Ngai, 1994), and while no exact population count exists for the species in the wild it has been estimated that there are close to 45,000 individuals living in Kaneohe Bay (McFall-Ngai, unpublished, 2017).It was found that 8-10 sexually mature pairs of adults could produce approximately 60,000 juveniles in one year when in captivity (McFall-Ngai, 2014).The main predators of the bobtail squid are fish, eels (Gillis, 1993), and crabs, though escape behavior such as jetting and inking may give the squid an advantage at avoiding being preyed upon (Anderson and Mather, 1996).There is currently not enough information on E. scolopes to determine if the population is threatened on a global scale (Barratt, I. & Allcock, L. 2012).
Mating in E. scolopes has been studied in laboratory settings.A male will gradually flatten itself on top of a female.It will then shift its position upward and move its arms underneath the female and the two will coil their arms together as a mass of sperm is transferred from the male to the female. (Moynihan, 1983).Females can lay 50-200 eggs per clutch.Unlike most species of cephalopod, females do not die after reproduction and can lay numerous clutches every few days (Montgomery and McFall-Ngai, 1993).Embryos will develop for approximately 20-23 days depending on environmental temperatures (Montgomery and McFall-Ngai, 1993), before hatching.
During the first hour after hatching, there is a permissive period in which many different kinds of bacteria enter a crypt in the tissue of the light organ from the surrounding seawater.However, at approximately the 1- 2 hour mark, a restrictive period occurs in which no bacteria can enter the organ.After this period, only V. fischeri are allowed to enter the squid’s light organ, and depending on the concentration of V. fischeri cells in the surrounding seawater, full colonization of the host can take between 8 and 48 hours (Nyholm and McFall-Ngai, 2004).
At dawn each day, adult bobtail squid expel 95% of the bacteria living in its light organ into the surrounding seawater (Visick and Ruby, 2008).Since juveniles stay within the vicinity of the parent population and do not disperse into the larger ecosystem, this daily expulsion and enrichment of V. fischeri from adults into the local environment is crucial for establishing the symbiosis wherein juveniles are colonized during their first minutes and hours of life (Nyholm and McFall-Ngai, 2004).
Euprymna scolopes (englisch Hawaiian bobtail squid) ist ein kleiner Zwergtintenfisch (33 bis 35 mm Mantellänge) der endemisch an der Küste Hawaiis vorkommt. Er besitzt keine interne Schale und hat zwei runde Flossen, deren Basis schmaler ist als die Länge der Flosse, was ihr ein ohrenähnliches Aussehen verleiht.
Junge und ausgewachsene Tiere leben vor allem in sehr flachen Küstengewässern, auch dort, wo das Wasser nur 2 bis 4 cm tief ist. Adulttiere wurden aber auch schon mit Schleppnetzen küstenfern in Tiefen von bis zu 250 Metern gefangen. Euprymna scolopes ist nachtaktiv und verbringt den Tag eingegraben im Sand, wobei nur die Augen sichtbar sind. Die Tiere sondern ein klebriges Sekret ab, welcher dazu dient, Sedimentpartikel auf den dorsalen Teil des Körpers, den "Rücken", zu binden und damit eine perfekte Tarnung zu gewährleisten. Seine Lebensdauer ist sehr kurz. Die Tiere erreichen die Geschlechtsreife im Alter von zwei Monaten und werden etwa ein Jahr alt – eine genaue Lebensdauer wurde bisher nicht ermittelt. Wie andere Kopffüßer vermehren sie sich nur einmal in ihrer Lebensspanne. Die Eier haben einen Durchmesser von 2 mm und werden an der Unterseite von Korallen abgelegt. Es gibt kein Larvenstadium, die Schlüpflinge sehen aus wie die Erwachsenen Tiere, nur sehr viel kleiner. Sie wachsen sehr schnell und ernähren sich in den ersten Tagen vom aufgenommenen Dotter.
In seinem natürlichen Lebensraum ernährt sich Euprymna scolopes vor allem von Garnelen, in Laboratorien gehaltene Tiere erbeuteten unter anderem auch Artemia, Schwebegarnelen und Gambusen. Euprymna scolopes selber wird von der Hawaii-Mönchsrobbe (Monachus schauinslandi) gefressen.[1]
Euprymna scolopes lebt mit der biolumineszenten Bakterienart Aliivibrio fischeri in Symbiose. Jungtiere sind noch ohne Symbiosebakterien. Sie werden dem umgebenden Meereswasser entnommen und durch ein Flimmerepithel in ein zweilappiges Leuchtorgan verbracht. Von diesem Leuchtorgan aus wird die gesamte Hautoberfläche des Zwergtintenfischs kolonisiert. Auf diese Weise emittiert Euprymna scolopes nachts Licht und wird im Mondlicht durch Produktion eines Gegenschattens nicht als Beute erkannt.[2]
Euprymna scolopes (englisch Hawaiian bobtail squid) ist ein kleiner Zwergtintenfisch (33 bis 35 mm Mantellänge) der endemisch an der Küste Hawaiis vorkommt. Er besitzt keine interne Schale und hat zwei runde Flossen, deren Basis schmaler ist als die Länge der Flosse, was ihr ein ohrenähnliches Aussehen verleiht.
Euprymna scolopes, also known as the Hawaiian bobtail squid, is a species of bobtail squid in the family Sepiolidae native to the central Pacific Ocean, where it occurs in shallow coastal waters off the Hawaiian Islands and Midway Island.[3][4] The type specimen was collected off the Hawaiian Islands and is deposited at the National Museum of Natural History in Washington, D.C.[5]
Euprymna scolopes grows to 30 mm (1.2 in) in mantle length.[3] Hatchlings weigh 0.005 g (0.00018 oz) and mature in 80 days. Adults weigh up to 2.67 g (0.094 oz).[6]
In the wild, E. scolopes feeds on species of shrimp, including Halocaridina rubra, Palaemon debilis, and Palaemon pacificus.[7] In the laboratory, E. scolopes has been reared on a varied diet of animals, including mysids (Anisomysis sp.), brine shrimp (Artemia salina), mosquitofish (Gambusia affinis), prawns (Leander debilis), and octopuses (Octopus cyanea).[8]
The Hawaiian monk seal (Monachus schauinslandi) preys on E. scolopes in northwestern Hawaiian waters.[9]
On June 3, 2021, SpaceX CRS-22 launched E. scolopes, along with tardigrades, to the International Space Station. The squid were launched as hatchlings and will be studied to see if they can incorporate their symbiotic bacteria into their light organ while in space.[10]
Euprymna scolopes lives in a symbiotic relationship with the bioluminescent bacteria Aliivibrio fischeri, which inhabits a special light organ in the squid's mantle. The bacteria are fed a sugar and amino acid solution by the squid and in return hide the squid's silhouette when viewed from below by matching the amount of light hitting the top of the mantle (counter-illumination).[11] E. scolopes serves as a model organism for animal-bacterial symbiosis and its relationship with A. fischeri has been carefully studied.[12][13][14][15][16][17][18][19]
The bioluminescent bacterium, A. fischeri, is horizontally transmitted throughout the E. scolopes population. Hatchlings lack these necessary bacteria and must carefully select for them in a marine world saturated with other microorganisms.[20]
To effectively capture these cells, E. scolopes secretes mucus in response to peptidoglycan (a major cell wall component of bacteria).[21] The mucus inundates the ciliated fields in the immediate area around the six pores of the light organ and captures a large variety of bacteria. However, by some unknown mechanism, A. fischeri is able to outcompete other bacteria in the mucus.[21]
As A. fischeri cells aggregate in the mucus, they must use their flagella to migrate through the pores and down into the ciliated ducts of the light organ and endure another barrage of host factors meant to ensure only A. fischeri colonization.[21] Besides the relentless host-derived current that forces motility-challenged bacteria out of the pores, a number of reactive oxygen species makes the environment unbearable.[21] Squid halide peroxidase is the main enzyme responsible for crafting this microbiocidal environment, using hydrogen peroxide as a substrate, but A. fischeri has evolved a brilliant counterattack. A. fischeri possesses a periplasmic catalase that captures hydrogen peroxide before it can be used by the squid halide peroxidase, thus inhibiting the enzyme indirectly.[21] Once through these ciliated ducts, A. fischeri cells swim on towards the antechamber, a large epithelial-lined space, and colonize the narrow epithelial crypts.[21]
The bacteria thrive on the host-derived amino acids and sugars in the antechamber and quickly fill the crypt spaces within 10 to 12 hours after hatching.[22]
Every second, a juvenile squid ventilates about 2.6 ml (0.092 imp fl oz; 0.088 US fl oz) of ambient seawater through its mantle cavity. Only a single A. fischeri cell, one/1-millionth of the total volume, is present with each ventilation.[21]
The increased amino acids and sugars feed the metabolically demanding bioluminescence of the A. fischeri, and in 12 hours, the bioluminescence peaks and the juvenile squid is able to counterilluminate less than a day after hatching.[22] Bioluminescence demands a substantial amount of energy from a bacterial cell. It is estimated to demand 20% of a cell's metabolic potential.[22]
Nonluminescent strains of A. fischeri would have a definite competitive advantage over the luminescent wild-type, however nonluminescent mutants are never found in the light organ of the E. scolopes.[22] In fact, experimental procedures have shown that removing the genes responsible for light production in A. fischeri drastically reduces colonization efficiency.[22] Luminescent cells, with functioning luciferase, may have a higher affinity for oxygen than for peroxidases, thereby negating the toxic effects of the peroxidases.[23] For this reason, bioluminescence is thought to have evolved as an ancient oxygen detoxification mechanism in bacteria.[23]
Despite all the effort that goes into obtaining luminescent A. fischeri, the host squid jettisons most of the cells daily. This process, known as “venting”, is responsible for the disposal of up to 95% of A. fischeri in the light organ every morning at dawn.[24] The bacteria gain no benefit from this behavior and the upside for the squid itself is not clearly understood. One reasonable explanation points to the large energy expenditure in maintaining a colony of bioluminescent bacteria.[25]
During the day when the squid are inactive and hidden, bioluminescence is unnecessary, and expelling the A. fischeri conserves energy. Another, more evolutionarily important reason may be that daily venting ensures selection for A. fischeri that have evolved specificity for a particular host, but can survive outside of the light organ.[26]
Since A. fischeri is transmitted horizontally in E. scolopes, maintaining a stable population of them in the open ocean is essential in supplying future generations of squid with functioning light organs.
The light organ has an electrical response when stimulated by light, which suggests the organ functions as a photoreceptor that enables the host squid to respond to A. fischeri's luminescence.[27]
Extraocular vesicles collaborate with the eyes to monitor the down-welling light and light created from counterillumination, so as the squid moves to various depths, it can maintain the proper level of output light.[25] Acting on this information, the squid can then adjust the intensity of the bioluminescence by modifying the ink sac, which functions as a diaphragm around the light organ.[25] Furthermore, the light organ contains a network of unique reflector and lens tissues that help reflect and focus the light ventrally through the mantle.[25]
The light organ of embryonic and juvenile squids has a striking anatomical similarity to an eye and expresses several genes similar to those involved in eye development in mammalian embryos (e.g. eya, dac) which indicate that squid eyes and squid light organs may be formed using the same developmental "toolkit".[28]
As the down-welling light increases or decreases, the squid is able to adjust luminescence accordingly, even over multiple cycles of light intensity.[25]
Euprymna scolopes, also known as the Hawaiian bobtail squid, is a species of bobtail squid in the family Sepiolidae native to the central Pacific Ocean, where it occurs in shallow coastal waters off the Hawaiian Islands and Midway Island. The type specimen was collected off the Hawaiian Islands and is deposited at the National Museum of Natural History in Washington, D.C.
Euprymna scolopes grows to 30 mm (1.2 in) in mantle length. Hatchlings weigh 0.005 g (0.00018 oz) and mature in 80 days. Adults weigh up to 2.67 g (0.094 oz).
In the wild, E. scolopes feeds on species of shrimp, including Halocaridina rubra, Palaemon debilis, and Palaemon pacificus. In the laboratory, E. scolopes has been reared on a varied diet of animals, including mysids (Anisomysis sp.), brine shrimp (Artemia salina), mosquitofish (Gambusia affinis), prawns (Leander debilis), and octopuses (Octopus cyanea).
The Hawaiian monk seal (Monachus schauinslandi) preys on E. scolopes in northwestern Hawaiian waters.
On June 3, 2021, SpaceX CRS-22 launched E. scolopes, along with tardigrades, to the International Space Station. The squid were launched as hatchlings and will be studied to see if they can incorporate their symbiotic bacteria into their light organ while in space.
Euprymna scolopes, el calamar hawaiano, es una especie de Sepiolida en la familia Sepiolidae nativa del océano Pacífico central, presente en aguas costeras poco profundas frente a las islas Hawái e islas Midway.[1][2] El espécimen tipo se recolectó aguas afuera de Hawái, y se halla en el National Museum of Natural History, Washington, D.C..[3]
E. scolopes crece hasta 30 mm de longitud de manto.[1] Una cría pesa 0,005 g y maturan en 80 días. El adulto pesa hasta 3 g.[4] Euprymna scolopes mantiene una estrecha colaboración con una bacteria bioluminiscente: Vibrio fischeri que lo ayudan a confundirse con el entorno mientras caza de noche. Comprender bien la relación que existe entre estas bacterias y el calamar hawaiano pudiera ser útil para desarrollar nuevos tratamientos médicos.
Los depredadores nocturnos de las cristalinas aguas de las playas de Hawái detectan a sus presas al ver su silueta recortada bajo la luz de la luna y las estrellas. Pero el calamar hawaiano hace desaparecer su silueta y también su sombra. ¿cómo? La parte de abajo del calamar se ilumina gracias a un órgano emisor de luz que alberga una colonia de bacterias bioluminiscentes. Ellas le permiten emitir una luz de la misma intensidad y longitud de onda que la iluminación del ambiente, lo que lo hace prácticamente invisible. Pero además esas bacterias contribuyen a regular los ciclos circadianos del calamar, es decir, sus periodos de actividad Y descanso. Al parecer hay otros organismos en los que las bacterias cumplen una función parecida. Por ejemplo, se ha dicho que ciertas bacterias digestivas de los mamíferos también están relacionadas con sus ciclos circadianos. Y puesto que la depresión, la diabetes, la obesidad y el insomnio pueden ser causados por alteraciones de estos ciclos, los científicos están estudiando la relación entre el calamar y las bacterias bioluminiscentes con el objetivo de crear nuevos tratamientos.[5]
Euprymna scolopes, el calamar hawaiano, es una especie de Sepiolida en la familia Sepiolidae nativa del océano Pacífico central, presente en aguas costeras poco profundas frente a las islas Hawái e islas Midway. El espécimen tipo se recolectó aguas afuera de Hawái, y se halla en el National Museum of Natural History, Washington, D.C..
E. scolopes crece hasta 30 mm de longitud de manto. Una cría pesa 0,005 g y maturan en 80 días. El adulto pesa hasta 3 g. Euprymna scolopes mantiene una estrecha colaboración con una bacteria bioluminiscente: Vibrio fischeri que lo ayudan a confundirse con el entorno mientras caza de noche. Comprender bien la relación que existe entre estas bacterias y el calamar hawaiano pudiera ser útil para desarrollar nuevos tratamientos médicos.
Los depredadores nocturnos de las cristalinas aguas de las playas de Hawái detectan a sus presas al ver su silueta recortada bajo la luz de la luna y las estrellas. Pero el calamar hawaiano hace desaparecer su silueta y también su sombra. ¿cómo? La parte de abajo del calamar se ilumina gracias a un órgano emisor de luz que alberga una colonia de bacterias bioluminiscentes. Ellas le permiten emitir una luz de la misma intensidad y longitud de onda que la iluminación del ambiente, lo que lo hace prácticamente invisible. Pero además esas bacterias contribuyen a regular los ciclos circadianos del calamar, es decir, sus periodos de actividad Y descanso. Al parecer hay otros organismos en los que las bacterias cumplen una función parecida. Por ejemplo, se ha dicho que ciertas bacterias digestivas de los mamíferos también están relacionadas con sus ciclos circadianos. Y puesto que la depresión, la diabetes, la obesidad y el insomnio pueden ser causados por alteraciones de estos ciclos, los científicos están estudiando la relación entre el calamar y las bacterias bioluminiscentes con el objetivo de crear nuevos tratamientos.
Euprymna scolopes est une espèce de seiche de la famille des Sepiolidae, vivant dans les eaux de l'océan Pacifique Central, au niveau de l'archipel d'Hawaï et de l'île Midway. C'est une espèce côtière, qui vit dans des eaux claires et peu profondes.
E. scolopes mesure en moyenne 35 mm pour 2,76 g, le mâle est légèrement plus grand que la femelle[1].
E. scolopes se nourrit essentiellement de quelques espèces de crevettes (Halocaridina rubra, Palaemon debilis, et Palaemon pacificus) mais des élevages en laboratoire ont montré qu'il était aussi capable de manger d'autres espèces de crevettes, de poissons et même d'autres céphalopodes.
E. scolopes est un organisme modèle en biologie pour l'étude des relations symbiotiques entre animaux et bactéries. Il vit en symbiose avec une bactérie bioluminescente, Aliivibrio fischeri, qui occupe un organe luminescent présent dans son manteau. Lors de ses sorties nocturnes, la lumière émise par les bactéries permet au calamar de dissimuler son ombre aux prédateurs, en produisant exactement autant de lumière en dessous de son corps que de lumière reçue par le dessus[2]. En retour, la bactérie pioche dans les réserves nutritives de son hôte.
La bactérie bioluminescente A. fischeri est logée dans un organe luminescent complexe, Photophore ou organe électroluminescent, dans la cavité du manteau de l'E. scolopes. Les vésicules extra oculaires permettent avec les yeux de surveiller les changements de lumière. Ainsi, E. scolopes peut maintenir le même niveau de luminescence tout en se déplaçant à différentes profondeurs. Il peut également changer, baisser le niveau d'éclairement pour échapper à ses prédateurs ou se cacher de ses proies. E. scolopes peut modifier l'intensité de la Bioluminescence grâce à une poche d'encre qui fonctionne comme un diaphragme autour de l'organe électroluminescent.[3]
Euprymna scolopes est une espèce de seiche de la famille des Sepiolidae, vivant dans les eaux de l'océan Pacifique Central, au niveau de l'archipel d'Hawaï et de l'île Midway. C'est une espèce côtière, qui vit dans des eaux claires et peu profondes.
Euprymna scolopes (conosciuto anche come calamaro delle Hawaii, in inglese Hawaiian Bobtail Squid) è una specie di mollusco cefalopode della famiglia Sepiolidae[2]. È originario dell'Oceano Pacifico centrale, dove si presenta in acque costiere poco profonde al largo delle Isole Hawaii e dell'Isola di Midway.[3][4] Il campione del tipo fu raccolto al largo delle Isole Hawaii ed è depositato al Museo Nazionale di Storia Naturale in Washington.[5]
L'E. scolopes cresce fino a 30 millimetri (1,2 in) di lunghezza del mantello.[3] I cuccioli pesano 0,005 grammi (0,00018 oz) e maturano in 80 giorni. Gli adulti pesano fino a 2,67 grammi (0,0094 oz).[6]
In natura, l'E. scolopes si nutre di specie di gamberetti, incluse Halocaridina rubra, Palaemon debilis e Palaemon pacificus.[7] In laboratorio, l'E. scolopes è stato allevato con una dieta variata di animali, compresi misidi (Anisomysis sp.), artemie (Artemia salina), pesci zanzara (Gambusia affinis), scampi (Leander debilis), e polpi (Octopus cyanea).[8]
La foca monaca delle Hawaii (Neomonachus schauinslandi) fa preda di E. scolopes nelle acque hawaiane nordoccidentali.[9]
E. scolopes vive in una relazione simbiotica con il batterio bioluminescente Vibrio fischeri, che abita uno speciale organo luminoso nel mantello del calamaro. I batteri sono alimentati dal calamaro con una soluzione di zuccheri e amminoacidi e in cambio ne nascondono la sagoma quando il calamaro è visto da sotto uguagliando la quantità di luce che colpisce la parte superiore del mantello (controilluminazione).[10] E. scolopes serve come organismo modello per la simbiosi animale-batterica e la sua relazione con V. fischeri è stata attentamente studiata.[11][12][13][14][15][16][17][18]
Il batterio bioluminescente, V. fischeri, si trasmette orizzontalmente in tutta la popolazione di E. scolopes. I cuccioli mancano di questi batteri necessari e devono selezionarli attentamente per sé in un mondo marino saturo di altri microorganismi.[19]
Al fine di poter catturare efficacemente queste cellule l'E. scolopes secerne del muco in risposta al peptidoglicano (un importante componente della parete cellulare dei batteri).[20] Il muco inonda i campi ciliati nell'area immediatamente intorno ai sei pori dell'organo luminoso e cattura una grande varietà di batteri. Tuttavia, per qualche meccanismo ignoto, il V. fischeri è in grado di estromettere gli altri batteri nel muco.[20]
Quando i V. fischeri si aggregano nel muco, devono usare i loro flagelli per migrare attraverso i pori e giù per i dotti ciliati dell'organo luminoso e superare un altro sbarramento di fattori dell'ospite destinati a garantire la colonizzazione soltanto dei V. fischeri.[20] Oltre all'incessante corrente prodotta dall'ospite che spinge i batteri dotati di ridotta motilità fuori dai pori, numerose specie reattive all'ossigeno rendono l'ambiente insopportabile.[20] L'alide perossidasi del calamaro è il principale enzima responsabile per creare questo ambiente microbicida, che usa come substrato il perossido di idrogeno, ma V. fischeri ha sviluppato un brillante contrattacco. V. fischeri possiede una catalase che cattura il perossido di idrogeno prima che possa essere usato dall'alide perossidasi del calamaro, inibendo così indirettamente l'enzima.[20] Una volta attraverso questi dotti ciliati, i V. fischeri avanzano nuotando verso l'anticamera, un grande spazio con un rivestimento epiteliale, e colonizzano le strette cripte epiteliali.[20]
I batteri prosperano sugli amminoacidi prodotti dall'ospite e sugli zuccheri nell'anticamera e riempiono rapidamente gli spazi delle cripte entro 10-12 ore dopo la schiusa.[21]
Ogni secondo un calamaro giovane ventila circa 2,6 millilitri (0,092 imp fl oz; 0,088 US fl oz) di acqua di mare ambientale attraverso la cavità del suo mantello. Soltanto una singola cellula di V. fischeri, 1 milionesimo del volume totale, è presente in ogni ventilazione.[20]
Gli aumentati amminoacidi e zuccheri alimentano la bioluminescenza ad alto consumo metabolico del V. fischeri e in 12 ore la bioluminescenza raggiunge il picco e il calamaro giovane è in grado di controilluminare meno di un giorno dopo la schiusa.[21] La bioluminescenza richiede un considerevole ammontare di energia a una cellula batterica. Si stima che richieda il 20% del potenziale metabolico della cellula.[21]
I ceppi di V. fischeri non luminescenti avrebbero un decisivo vantaggio competitivo sul tipo naturale luminescente. Tuttavia i mutanti non luminescenti non si trovano mai nell'organo luminoso dell'E. scolopes.[21] In realtà, i processi sperimentali hanno mostrato che rimuovere i geni responsabili della produzione di luce nel V. fischeri riduce drasticamente l'efficienza della colonizzazione.[21] Può darsi che le cellule luminescenti, con la luciferasi funzionante, abbiano una maggiore affinità per l'ossigeno che per la perossidasi, annullando in tal modo gli effetti tossici della perossidasi.[22] Per questa ragione, si pensa che la bioluminescenza si sia evoluta come un antico meccanismo di disintossicazione dell'ossigeno nei batteri.[22]
Malgrado tutto lo sforzo impiegato nell'ottenere i V. fischeri luminescenti, i calamari ospiti eliminano in mare giornalmente la maggior parte delle cellule. Questo processo, conosciuto come "sfiatamento" (in inglese venting), è responsabile dello smaltimento fino al 95% di V. fischeri nell'organo luminoso all'alba.[23] I batteri non ottengono alcun beneficio da questo comportamento e l'aspetto positivo per lo stesso calamaro non è molto chiaro. Una spiegazione ragionevole si riferisce al grande dispendio energetico nel mantenere una colonia di batteri bioluminescenti.[24]
Durante il giorno quando i calamari sono inattivi e nascosti, la bioluminescenza non è necessaria ed espellendo i V. fischeri conserva energia. Un'altra ragione, evolutivamente più importante, può essere che lo sfiatamento quotidiano assicura la selezione di V. fischeri che hanno sviluppato la specificità per un particolare ospite, ma possono sopravvivere al di fuori dell'organo luminoso.[25]
Poiché i V. fischeri si trasmettono orizzontalmente negli E. scolopes, mantenere una popolazione stabile di essi nell'oceano aperto è essenziale per fornire alle future generazioni di calamari organi luminosi funzionanti.
L'organo luminoso ha una risposta elettrica quando viene stimolato dalla luce, il che suggerisce che l'organo funzioni come un fotorecettore che consente al calamaro ospite di rispondere alla luminescenza del V. fischeri.[26]
Vescicole extra-oculari collaborano con gli occhi per monitorare la luce che scende verso il basso e quella creata dalla controilluminazione, così mentre il calamaro si muove a varie profondità può mantenere il livello appropriato di emissione luminosa.[24] Agendo su questa informazione, il calamaro può poi regolare l'intensità della bioluminescenza modificando il sacco dell'inchiostro, che funziona come un diaframma intorno all'organo luminoso.[24] Inoltre, l'organo luminoso contiene una rete di tessuti unici che fungono da riflettori e da lenti e aiutano a riflettere e focalizzare la luce ventralmente attraverso il mantello.[24]
L'organo luminoso dei calamari embrionali e giovani ha un'impressionante somiglianza anatomica con un occhio ed esprime parecchi geni simili a quelli coinvolti nello sviluppo oculare negli embrioni mammiferi (ad es. eya, dac), il che indica che gli occhi e gli organi luminosi dei calamari possono essere formati usando lo stesso "software" di sviluppo.
Quando la luce in discesa aumenta o diminuisce, il calamaro è in grado di regolare la luminescenza in maniera conseguente, perfino durante molteplici cicli di intensità luminosa.[24]
Euprymna scolopes (conosciuto anche come calamaro delle Hawaii, in inglese Hawaiian Bobtail Squid) è una specie di mollusco cefalopode della famiglia Sepiolidae. È originario dell'Oceano Pacifico centrale, dove si presenta in acque costiere poco profonde al largo delle Isole Hawaii e dell'Isola di Midway. Il campione del tipo fu raccolto al largo delle Isole Hawaii ed è depositato al Museo Nazionale di Storia Naturale in Washington.
L'E. scolopes cresce fino a 30 millimetri (1,2 in) di lunghezza del mantello. I cuccioli pesano 0,005 grammi (0,00018 oz) e maturano in 80 giorni. Gli adulti pesano fino a 2,67 grammi (0,0094 oz).
In natura, l'E. scolopes si nutre di specie di gamberetti, incluse Halocaridina rubra, Palaemon debilis e Palaemon pacificus. In laboratorio, l'E. scolopes è stato allevato con una dieta variata di animali, compresi misidi (Anisomysis sp.), artemie (Artemia salina), pesci zanzara (Gambusia affinis), scampi (Leander debilis), e polpi (Octopus cyanea).
La foca monaca delle Hawaii (Neomonachus schauinslandi) fa preda di E. scolopes nelle acque hawaiane nordoccidentali.
Euprymna scolopes is een inktvis die voorkomt in de Grote Oceaan. Hij wordt meestal aangetroffen in de kustwateren van de Hawaï-Eilanden en het eiland Midway.[1][2] De typesoort is afkomstig van Hawaï en is te zien in het National Museum of Natural History in Washington, D.C..[3]
E. scolopes groeit tot een 30 mm in mantellengte[1] Als ze uit het eitje komen wegen ze 0,005 g na 80 dagen zijn ze volwassen en wegen ze tot 2,67 g.[4]
E. scolopes voedt zich met garnaalachtigen zoals.Halocaridina rubra, Palaemon debilis, en Palaemon pacificus.[5] In gevangenschap hebben ze het dier met succes gevoed met een dieet van aasgarnalen, Artemia salina, Gambusia affinis, Leander debilis, en Octopus cyanea.[6]
E. scolopes is een prooi van de Hawaïaanse monniksrob (Monachus schauinslandi).[7]
E. scolopes leeft in a symbiose met de bioluminescente bacterie Vibrio fischeri, die zich in een speciaal lichtgevend orgaan in de mantelholte bevindt. De bacteriën worden gevoed door een suiker en aminozuren oplossing afkomstig van de inktvis die op zijn beurt beschermd wordt. Het licht dat het orgaan geeft, wist als het ware de schaduw uit die de inktvis op de bodem werpt als hij bij maanlicht naar voedsel zoekt.[8]
Euprymna scolopes is een inktvis die voorkomt in de Grote Oceaan. Hij wordt meestal aangetroffen in de kustwateren van de Hawaï-Eilanden en het eiland Midway. De typesoort is afkomstig van Hawaï en is te zien in het National Museum of Natural History in Washington, D.C..
E. scolopes groeit tot een 30 mm in mantellengte Als ze uit het eitje komen wegen ze 0,005 g na 80 dagen zijn ze volwassen en wegen ze tot 2,67 g.
E. scolopes voedt zich met garnaalachtigen zoals.Halocaridina rubra, Palaemon debilis, en Palaemon pacificus. In gevangenschap hebben ze het dier met succes gevoed met een dieet van aasgarnalen, Artemia salina, Gambusia affinis, Leander debilis, en Octopus cyanea.
E. scolopes is een prooi van de Hawaïaanse monniksrob (Monachus schauinslandi).
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