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61-542: See text Elasmobranchs lack swim bladders , and maintain buoyancy with oil that they store in their livers. Some deep sea sharks are targeted by fisheries for this liver oil , including the school , gulper and basking sharks (pictured) . All three of these species have been assessed by the IUCN as vulnerable due to overfishing . From a practical point of view the life-history pattern of elasmobranchs makes this group of animals extremely susceptible to over fishing. It

122-425: A blue appearance, which shifts to yellow with age, with adult coloration ranging from light orange to green. While enhancing night vision, increased light scatter within the tapetum slightly compromises visual acuity. Kiwis , stone-curlews , the boat-billed heron , the flightless kākāpō , and many nightjars , owls , and other night birds such as the swallow-tailed gull possess a tapetum lucidum. Nightjars use

183-468: A false sea floor 300–500 metres deep at day, and less deep at night. This turned out to be due to millions of marine organisms, most particularly small mesopelagic fish, with swimbladders that reflected the sonar. These organisms migrate up into shallower water at dusk to feed on plankton. The layer is deeper when the moon is out, and can become shallower when clouds obscure the moon. Most mesopelagic fish make daily vertical migrations , moving at night into

244-420: A gas bladder. Physoclisti can not expel air quickly enough from the gas bladder, the organ most susceptible to sonic damage, thus making it difficult for them to escape major injury. Physostomes, on the other hand, can release air from their gas bladder expeditiously enough to protect it; nevertheless, they can not relieve pressure in their other vital organs, and are therefore also vulnerable to injury. Some of

305-606: A monophyletic superorder within Elasmobranchii that shares a common ancestor with the selachians. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Swim bladder The swim bladder is evolutionarily homologous to the lungs of tetrapods and lungfish , and some ray-finned fish such as bowfins have also evolved similar respiratory functions in their swim bladders. Charles Darwin remarked upon this in On

366-480: A neutral or near-neutral buoyancy, which cannot be readily changed with depth. The swim bladder normally consists of two gas-filled sacs located in the dorsal portion of the fish, although in a few primitive species, there is only a single sac. It has flexible walls that contract or expand according to the ambient pressure . The walls of the bladder contain very few blood vessels and are lined with guanine crystals, which make them impermeable to gases. By adjusting

427-643: A number of other extinct chondrichthyans with Elasmobrachii sensu stricto /Neoselachii, to the exclusion of more primitive total group elasmobranchs, which is supported by a number of shared morphological characters of the skeleton. The 5th edition of Fishes of the World sets out the following classification of the Elasmobranchs: Recent molecular studies suggest the Batoidea are not derived selachians as previously thought. Instead, skates and rays are

488-565: A nutrient when food is scarce. The oldest unambigous total group elasmobranch, Phoebodus , has its earliest records in the Middle Devonian (late Givetian ), around 383 million years ago. Several important groups of total group elasmobranchs, including Ctenacanthiformes and Hybodontiformes , had already emerged by the latest Devonian ( Famennian ). During the Carboniferous , some ctenacanths would grow to sizes rivalling

549-517: A retinal tapetum lucidum composed of lipids. Most species of spider also have a tapetum, which is located only in their smaller, lateral eyes; the larger central eyes have no such structure. This consists of reflective crystalline deposits and is thought to have a similar function to the structure of the same name in vertebrates. Four general patterns can be distinguished in spiders: Animals without tapetum lucidum include haplorhine primates, squirrels, some birds, red kangaroo , and pigs. Eyeshine

610-414: A similar manner. In more derived varieties of fish (the physoclisti ), the connection to the digestive tract is lost. In early life stages, these fish must rise to the surface to fill up their swim bladders; in later stages, the pneumatic duct disappears, and the gas gland has to introduce gas (usually oxygen ) to the bladder to increase its volume and thus increase buoyancy . This process begins with

671-467: A similar structure known as the 'oval window', the bladder is in contact with blood and the oxygen can diffuse back out again. Together with oxygen, other gases are salted out in the swim bladder which accounts for the high pressures of other gases as well. The combination of gases in the bladder varies. In shallow water fish, the ratios closely approximate that of the atmosphere , while deep sea fish tend to have higher percentages of oxygen. For instance,

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732-406: A special swim bladder that allows the jellyfish-like colonies to float along the surface of the water while their tentacles trail below. This organ is unrelated to the one in fish. t Tapetum lucidum The tapetum lucidum ( Latin for 'bright tapestry, coverlet'; / t ə ˈ p iː t əm ˈ l uː s ɪ d əm / tə- PEE -təm LOO -sih-dəm ; pl. : tapeta lucida )

793-466: A tapetum lucidum is present, its location on the eyeball varies with the placement of the eyeball in the head. Apart from its eyeshine, the tapetum lucidum itself has a color. It is often described as iridescent. In tigers , it is greenish. In ruminants , it may be golden green with a blue periphery, or whitish or pale blue with a lavender periphery. In dogs , it may be whitish with a blue periphery. The color in reindeer changes seasonally, allowing

854-449: A tapetum lucidum. The presence of a tapetum lucidum enables animals to see in dimmer light than would otherwise be possible. The tapetum lucidum, which is iridescent , reflects light roughly on the interference principles of thin-film optics , as seen in other iridescent tissues. However, the tapetum lucidum cells are leucophores , not iridophores . The tapetum functions as a retroreflector which reflects light directly back along

915-618: A widely different purpose, namely, respiration. The swim bladder has, also, been worked in as an accessory to the auditory organs of certain fishes. All physiologists admit that the swimbladder is homologous, or “ideally similar” in position and structure with the lungs of the higher vertebrate animals: hence there is no reason to doubt that the swim bladder has actually been converted into lungs, or an organ used exclusively for respiration. According to this view it may be inferred that all vertebrate animals with true lungs are descended by ordinary generation from an ancient and unknown prototype, which

976-598: Is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina , it is a retroreflector . It reflects visible light back through the retina, increasing the light available to the photoreceptors (although slightly blurring the image). The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal , especially carnivores , while others are deep-sea animals . Similar adaptations occur in some species of spiders . Haplorhine primates , including humans, are diurnal and lack

1037-408: Is a type of iridescence , the color varies with the angle at which it is seen and the minerals which make up the reflective tapetum lucidum crystals. Individuals with heterochromia may display red eyeshine in the blue eye and other-colored eyeshine in the other eye. These include odd-eyed cats and bi-eyed dogs . Although human eyes lack a tapetum lucidum, they still exhibit a weak reflection from

1098-494: Is a visible effect of the tapetum lucidum. When light shines into the eye of an animal having a tapetum lucidum, the pupil appears to glow. Eyeshine can be seen in many animals, in nature, and in flash photographs . In low light, a hand-held flashlight is sufficient to produce eyeshine that is visible to humans (despite their inferior night vision ). Eyeshine occurs in a wide variety of colors including white , blue , green , yellow , pink , and red . However, since eyeshine

1159-437: Is articulated with the upper. Extant elasmobranchs exhibit several archetypal jaw suspensions: amphistyly, orbitostyly, hyostyly, and euhyostyly. In amphistyly, the palatoquadrate has a postorbital articulation with the chondrocranium from which ligaments primarily suspend it anteriorly. The hyoid articulates with the mandibular arch posteriorly, but it appears to provide little support to the upper and lower jaws. In orbitostyly,

1220-481: Is interconnected with the inner ear of the fish. They are connected by four bones called the Weberian ossicles from the Weberian apparatus . These bones can carry the vibrations to the saccule and the lagena . They are suited for detecting sound and vibrations due to its low density in comparison to the density of the fish's body tissues. This increases the ability of sound detection. The swim bladder can radiate

1281-515: Is no coincidence that the commercially exploited marine turtles and baleen whales, which have life-history patterns similar to the sharks, are also in trouble. Elasmobranchii ( / ɪ ˌ l æ z m ə ˈ b r æ ŋ k i aɪ / ) is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks (superorder Selachii), rays , skates , and sawfish (superorder Batoidea ). Members of this subclass are characterised by having five to seven pairs of gill clefts opening individually to

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1342-639: Is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil. The definition of the clade is unclear with respect to fossil chondrichthyans. Some authors consider it as equivalent to Neoselachii (the crown group clade including modern sharks, rays, and all other descendants of their last common ancestor ). Other authors use the name Elasmobranchii for a broader branch-based group of all chondrichthyans more closely related to modern sharks and rays than to Holocephali (the clade containing chimaeras and their extinct relatives). Important extinct groups of elasmobranchs sensu lato include

1403-410: Is one of the two subclasses of cartilaginous fish in the class Chondrichthyes , the other being Holocephali ( chimaeras ). Members of the elasmobranchii subclass have no swim bladders , five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins , and small placoid scales . The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw

1464-441: Is renowned for its brilliance, even inspiring ancient Egyptians to believe it reflected the sun at night. This reflective layer, composed of 15-20 layers of cells centrally. This cellular structure, denser than that of dogs, results in high reflectance, nearly 130 times that of humans. Its color is heterogeneous, varying with age and species due to factors like rodlet spacing, refractive index, and light interactions. Young cats exhibit

1525-491: The Actinopteri (ray-finned fish minus the bichirs ) the lungs evolved into a swim bladder (secondary absent in some lineages), which unlike lungs that bud ventrally, buds dorsally from the anterior foregut. Coelacanths have a "fatty organ" that have sometimes been referred to as a swim bladder, but is structurally different and have a separate evolutionary history. In 1997, Farmer proposed that lungs evolved to supply

1586-463: The choroid , as can be seen in photography with the red-eye effect and with near-infrared eyeshine. Another effect in humans and other animals that may resemble eyeshine is leukocoria , which is a white shine indicative of abnormalities such as cataracts and cancers . Humans can scan for eyeshine to detect and identify the species of animals in the dark and deploy search dogs and search horses at night. The color corresponds approximately to

1647-451: The eel Synaphobranchus has been observed to have 75.1% oxygen, 20.5% nitrogen , 3.1% carbon dioxide , and 0.4% argon in its swim bladder. Physoclist swim bladders have one important disadvantage: they prohibit fast rising, as the bladder would burst. Physostomes can "burp" out gas, though this complicates the process of re-submergence. The swim bladder in some species, mainly fresh water fishes ( common carp , catfish , bowfin )

1708-490: The hybodonts (Order Hybodontiformes), xenacanths (order Xenacanthformes) and Ctenacanthiformes . These are also often referred to as "sharks" in reference to their similar anatomy and ecology to modern sharks. The name Elasmobranchii comes from the Ancient Greek words elasmo- ("plate") and bránchia ("gill"), referring to the broad, flattened gills which are characteristic of these fishes. Elasmobranchii

1769-429: The rete mirabile , and as a result, virtually all the excess carbon dioxide and oxygen produced in the gas gland diffuses back to the arteries supplying the gas gland via a countercurrent multiplication loop . Thus a very high gas pressure of oxygen can be obtained, which can even account for the presence of gas in the swim bladders of deep sea fish like the eel , requiring a pressure of hundreds of bars . Elsewhere, at

1830-447: The suboptimal design of the vertebrate retina. Traditionally, it has been difficult to take retinal images of animals with a tapetum lucidum because ophthalmoscopy devices designed for humans rely on a high level of on-axis illumination. This kind of illumination causes backscatter when it interacts with the tapetum. New devices with variable illumination can make this possible, however. In dogs, certain drugs are known to disturb

1891-475: The Origin of Species , and reasoned that the lung in air-breathing vertebrates had derived from a more primitive swim bladder as a specialized form of enteral respiration . In the embryonic stages, some species, such as redlip blenny , have lost the swim bladder again, mostly bottom dwellers like the weather fish . Other fish — like the opah and the pomfret — use their pectoral fins to swim and balance

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1952-554: The Triassic and Early Jurassic . Hybodonts were extensively present in both marine and freshwater environments. While Neoselachii/Elasmobranchi sensu stricto (the group of modern sharks and rays) had already appeared by the Triassic, they only had low diversity during this period would and only begin to extensively diversify from the Early Jurassic onwards, when modern orders of sharks and rays appeared. This co-incided with

2013-401: The acidification of the blood in the rete mirabile when the gas gland excretes lactic acid and produces carbon dioxide , the latter of which acidifies the blood via the bicarbonate buffer system . The resulting acidity causes the hemoglobin of the blood to lose its oxygen ( Root effect ) which then diffuses partly into the swim bladder. Before returning to the body, the blood re-enters

2074-413: The animals to better avoid predators in low-light winter at the price of blurrier vision. A classification of anatomical variants of tapeta lucida defines four types: The functional differences between these four structural classes of tapeta lucida are not known. Humans like haplorhine primates lack a tapetum lucidum as they are diurnal . Strepsirrhine primates are mostly nocturnal and, with

2135-443: The clarification of beer . In earlier times, they were used to make condoms . Swim bladder disease is a common ailment in aquarium fish . A fish with swim bladder disorder can float nose down tail up, or can float to the top or sink to the bottom of the aquarium. Many anthropogenic activities, such as pile driving or even seismic waves , can create high-intensity sound waves that cause internal injury to fish that possess

2196-534: The commonly seen injuries include ruptured gas bladder and renal Haemorrhage . These mostly affect the overall health of the fish but not their mortality rate. Investigators employed the High-Intensity-Controlled Impedance-Fluid-Filled (HICI-FT), a stainless-steel wave tube with an electromagnetic shaker. It simulates high-energy sound waves in aquatic far-field, plane-wave acoustic conditions. Siphonophores have

2257-643: The cranium. Instead, the hyomandibular cartilages provide the only means of jaw support, while the ceratohyal and basihyal elements articulate with the lower jaw, but are disconnected from the rest of the hyoid. The eyes have a tapetum lucidum . The inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm . These fish are widely distributed in tropical and temperate waters. Many fish maintain buoyancy with swim bladders . However elasmobranchs lack swim bladders, and maintain buoyancy instead with large livers that are full of oil. This stored oil may also function as

2318-617: The decline of the hybodonts, which had become minor components of marine environments by the Late Jurassic, but would remain common in freshwater environments into the Cretaceous . The youngest remains of hybodonts date to the very end of the Cretaceous. Elasmobranchii was first coined in 1838 by Charles Lucien Bonaparte . Bonaparte's original definition of Elasmobranchii was effectively identical to modern Chondrichthyes , and

2379-407: The epipelagic zone, often following similar migrations of zooplankton, and returning to the depths for safety during the day. These vertical migrations often occur over large vertical distances, and are undertaken with the assistance of a swim bladder. The swim bladder is inflated when the fish wants to move up, and, given the high pressures in the mesoplegic zone, this requires significant energy. As

2440-764: The exception of several diurnal Eulemur species, have a tapetum lucidum of riboflavin crystals. In canids, the tapetum lucidum is found in the dorsal half of the eye's fundus. It consists of 9-20 layers of specialized rectangular cells between the choroid and retinal pigment epithelium, thinning towards the periphery. The cells contain zinc-rich rodlets arranged in parallel. The structure appears yellow-green in adults, though blue in puppies until four months of age. Zinc concentration varies among species, with red foxes showing highest levels, followed by Arctic foxes, then domestic dogs. A hereditary zinc-deficiency condition in some beagles results in degenerated tapetal cells with disrupted rodlet arrangement. The tapetum lucidum in cats

2501-402: The exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades . The pelvic fins in males are modified to create claspers for the transfer of sperm. There

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2562-508: The fish ascends, the pressure in the swimbladder must adjust to prevent it from bursting. When the fish wants to return to the depths, the swimbladder is deflated. Some mesopelagic fishes make daily migrations through the thermocline , where the temperature changes between 10 and 20 °C, thus displaying considerable tolerance for temperature change. Sampling via deep trawling indicates that lanternfish account for as much as 65% of all deep sea fish biomass . Indeed, lanternfish are among

2623-427: The gas pressurising organ using the gas gland or oval window, the fish can obtain neutral buoyancy and ascend and descend to a large range of depths. Due to the dorsal position it gives the fish lateral stability. In physostomous swim bladders, a connection is retained between the swim bladder and the gut , the pneumatic duct, allowing the fish to fill up the swim bladder by "gulping" air. Excess gas can be removed in

2684-439: The heart with oxygen. In fish, blood circulates from the gills to the skeletal muscle, and only then to the heart. During intense exercise, the oxygen in the blood gets used by the skeletal muscle before the blood reaches the heart. Primitive lungs gave an advantage by supplying the heart with oxygenated blood via the cardiac shunt. This theory is robustly supported by the fossil record, the ecology of extant air-breathing fishes, and

2745-542: The last common ancestor of modern sharks and rays, a grouping which had previously been named Neoselachii by Compagno (1977). Other recent authors have used Elasmobranchii in a broad sense to include all chondrichthyans more closely related to modern sharks and rays than to chimaeras. The total group of Elasmobranchii includes the Cohort Euselachii Hay, 1902, which groups the Hybodontiformes and

2806-421: The light path. This serves to match the original and reflected light, thus maintaining the sharpness and contrast of the image on the retina. The tapetum lucidum reflects with constructive interference , thus increasing the quantity of light passing through the retina. In the cat, the tapetum lucidum increases the sensitivity of vision by 44%, allowing the cat to see light that is imperceptible to human eyes. When

2867-581: The millions of lanternfish swim bladders, giving the appearance of a false bottom. In the East Asian culinary sphere, the swim bladders of certain large fishes are considered a food delicacy. In Chinese cuisine, they are known as fish maw , 花膠/鱼鳔, and are served in soups or stews. The vanity price of a vanishing kind of maw is behind the imminent extinction of the vaquita , the world's smallest porpoise species. Found only in Mexico's Gulf of California ,

2928-579: The modern great white shark with bodies in the region of 7 metres (23 ft) in length. During the Carboniferous and Permian , the xenacanths were abundant in both freshwater and marine environments, and would continue to exist into the Triassic with reduced diversity. The hybodonts had achieved a high diversity by the Permian, and would end up becoming the dominant group of elasmobranchs during

2989-399: The most widely distributed, populous, and diverse of all vertebrates , playing an important ecological role as prey for larger organisms. The estimated global biomass of lanternfish is 550–660 million tonnes , several times the annual world fisheries catch. Lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans. Sonar reflects off

3050-407: The necessary lift needed due to the lack of swim bladders. Teleost fish with swim bladders have neutral buoyancy, and have no need for this lift. The swim bladder of a fish can strongly reflect sound of an appropriate frequency. Strong reflection happens if the frequency is tuned to the volume resonance of the swim bladder. This can be calculated by knowing a number of properties of the fish, notably

3111-407: The once numerous vaquita are now critically endangered. Vaquita die in gillnets set to catch totoaba (the world's largest drum fish ). Totoaba are being hunted to extinction for its maw, which can sell for as much $ 10,000 per kilogram. Swim bladders are also used in the food industry as a source of collagen . They can be made into a strong, water-resistant glue, or used to make isinglass for

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3172-412: The orbital process hinges with the orbital wall and the hyoid provides the majority of suspensory support. In contrast, hyostyly involves an ethmoid articulation between the upper jaw and the cranium, while the hyoid most likely provides vastly more jaw support compared to the anterior ligaments. Finally, in euhyostyly, also known as true hyostyly, the mandibular cartilages lack a ligamentous connection to

3233-431: The physiology of extant fishes. In embryonal development, both lung and swim bladder originate as an outpocketing from the gut; in the case of swim bladders, this connection to the gut continues to exist as the pneumatic duct in the more "primitive" ray-finned fish, and is lost in some of the more derived teleost orders. There are no animals which have both lungs and a swim bladder. As an adaptation to migrations between

3294-504: The pressure of sound which help increase its sensitivity and expand its hearing. In some deep sea fishes like the Antimora , the swim bladder maybe also connected to the macula of saccule in order for the inner ear to receive a sensation from the sound pressure. In red-bellied piranha , the swim bladder may play an important role in sound production as a resonator. The sounds created by piranhas are generated through rapid contractions of

3355-522: The sonic muscles and is associated with the swim bladder. Teleosts are thought to lack a sense of absolute hydrostatic pressure , which could be used to determine absolute depth. However, it has been suggested that teleosts may be able to determine their depth by sensing the rate of change of swim-bladder volume. The illustration of the swim bladder in fishes ... shows us clearly the highly important fact that an organ originally constructed for one purpose, namely, flotation, may be converted into one for

3416-479: The surface and deeper waters, some fish have evolved a swim bladder where the gas is replaced with low-density wax esters as a way to cope with Boyle's law . The cartilaginous fish (e.g., sharks and rays) split from the other fishes about 420 million years ago, and lack both lungs and swim bladders, suggesting that these structures evolved after that split. Correspondingly, these fish also have both heterocercal and stiff, wing-like pectoral fins which provide

3477-519: The type of tapetum lucidum, with some variation between species. It has been speculated that some flashlight fish may use eyeshine both to detect and to communicate with other flashlight fish. American scientist Nathan H. Lents has proposed that the tapetum lucidum evolved in vertebrates, but not in cephalopods , which have a very similar eye because of the backwards-facing nature of vertebrate photoreceptors. The tapetum boosts photosensitivity under conditions of low illumination, thus compensating for

3538-452: The volume of the swim bladder, although the well-accepted method for doing so requires correction factors for gas-bearing zooplankton where the radius of the swim bladder is less than about 5 cm. This is important, since sonar scattering is used to estimate the biomass of commercially- and environmentally-important fish species. Sonar operators, using the newly developed sonar technology during World War II, were puzzled by what appeared to be

3599-552: The weight of the head to keep a horizontal position. The normally bottom-dwelling sea robin can use their pectoral fins to produce lift while swimming like cartilaginous fish do. The gas/tissue interface at the swim bladder produces a strong reflection of sound, which is used by sonar equipment to find fish . Cartilaginous fish, such as sharks and rays , do not have swim bladders. Some of them can control their depth only by swimming (using dynamic lift ); others store up lipids with density less than that of seawater to produce

3660-432: Was based around gill architecture shared by all 3 living major cartilaginous fish groups. During the 20th century it became standard to exclude chimaeras from Elasmobranchii; along with including many fossil chondrichthyans within the group. The definition of Elasmobranchii has since been subject to much confusion with regard to fossil chondrichthyans. Maisey (2012) suggested that Elasmobranchii should exclusively be used for

3721-497: Was furnished with a floating apparatus or swim bladder. Charles Darwin , 1859 Swim bladders are evolutionarily closely related (i.e., homologous ) to lungs . The first lungs originated in the last common ancestor of the Actinopterygii (ray-finned fish) and Sarcopterygii (lobe-finned fish and the tetrapods ) as expansions of the upper digestive tract which allowed them to gulp air under oxygen-poor conditions. In

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