66-651: Ameca may refer to: Biology [ edit ] Ameca (fish) , a monotypic ray-finned fish genus in the family Goodeidae, with the only species Ameca splendens Places in Mexico [ edit ] Ameca, Jalisco , a city and municipality in central Jalisco Chiefdom of Ameca , a pre-Columbian state in Jalisco Ameca Valley , a large expansive plateau in Jalisco Ameca River Amecameca , in
132-418: A blunt, flexible andropodium used for mating. As usual in live-bearers, males are the smaller sex, reaching some 3 in (7–8 cm) total length at best, with females being able to grow up to 4 in (10 cm) under good conditions. The butterfly splitfin is placed in the monotypic genus Ameca . Phylogenic research by Shane Webb showed that its closest relative is Xenotaca variata , and that X. variata
198-430: A different reason. Unlike dolphins, these fish do not feel the bubbles, because they have bony fins without nerve endings. Nevertheless, they cannot swim faster because the cavitation bubbles create a vapor film around their fins that limits their speed. Lesions have been found on tuna that are consistent with cavitation damage. Scombrid fishes (tuna, mackerel and bonito) are particularly high-performance swimmers. Along
264-442: A homocercal tail. These come in a variety of shapes, and can appear: (D) - Diphycercal means the vertebrae extend to the tip of the tail and the tail is symmetrical and expanded (as in the bichir , lungfish , lamprey , coelacanths and † Tarrasiiformes ). Most Palaeozoic fishes had a diphycercal heterocercal tail. Finlets are small fins, generally behind the dorsal and anal fins (in bichirs , there are only finlets on
330-515: A liquid, which then promptly and violently collapse. It can cause significant damage and wear. Cavitation damage can occur to the tail fins of powerful swimming marine animals, such as dolphins and tuna. Cavitation is more likely to occur near the surface of the ocean, where the ambient water pressure is relatively low. Even if they have the power to swim faster, dolphins may have to restrict their speed because collapsing cavitation bubbles on their tail are too painful. Cavitation also slows tuna, but for
396-532: A loose dominance hierarchy develops, in particular in confined environments. Males chase each other about, with the dominant male(s) showing the most splendid coloration. Submissive males will try to retreat from attacks, typically towards the surface, and may shake their head as a calming signal . Like other Goodeidae , butterfly splitfins mate by internal fertilization and spawn fully developed young. The females become sexually mature at about six months of age and can give birth every six to 10 weeks according to
462-508: A modified fin to deliver sperm; thresher sharks use their caudal fin to whip and stun prey; reef stonefish have spines in their dorsal fins that inject venom as an anti-predator defense ; anglerfish use the first spine of their dorsal fin like a fishing rod to lure prey; and triggerfish avoid predators by squeezing into coral crevices and using spines in their fins to anchor themselves in place. Fins can either be paired or unpaired . The pectoral and pelvic fins are paired, whereas
528-439: A more disproportionate way than other fins on female fish." There are two prevailing hypotheses that have been historically debated as models for the evolution of paired fins in fish: the gill arch theory and the lateral fin-fold theory. The former, commonly referred to as the " Gegenbaur hypothesis ," was posited in 1870 and proposes that the "paired fins are derived from gill structures". This fell out of popularity in favor of
594-416: A neural network in the fin, indicating that it likely has a sensory function, but are still not sure exactly what the consequences of removing it are. A comparative study in 2013 indicates the adipose fin can develop in two different ways. One is the salmoniform-type way, where the adipose fin develops from the larval-fin fold at the same time and in the same direct manner as the other median fins. The other
660-705: A pancake, and will fit into fissures in rocks. Their pelvic and pectoral fins have evolved differently, so they act together with the flattened body to optimise manoeuvrability. Some fishes, such as puffer fish , filefish and trunkfish , rely on pectoral fins for swimming and hardly use tail fins at all. Male cartilaginous fishes (sharks and rays), as well as the males of some live-bearing ray finned fishes , have fins that have been modified to function as intromittent organs , reproductive appendages which allow internal fertilization . In ray finned fish, they are called gonopodia or andropodia , and in cartilaginous fish, they are called claspers . Gonopodia are found on
726-549: A prominent dorsal fin. Like scombroids and other billfish , they streamline themselves by retracting their dorsal fins into a groove in their body when they swim. The huge dorsal fin, or sail, of the sailfish is kept retracted most of the time. Sailfish raise them if they want to herd a school of small fish, and also after periods of high activity, presumably to cool down. The oriental flying gurnard has large pectoral fins which it normally holds against its body, and expands when threatened to scare predators. Despite its name, it
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#1732852111403792-454: A thin stretch of scaleless skin ; in lobe-finned fish ( Sarcopterygii ) such as coelacanths and lungfish , fins are short rays based around a muscular central bud supported by jointed bones ; in cartilaginous fish ( Chondrichthyes ) and jawless fish ( Agnatha ), fins are fleshy " flippers " supported by a cartilaginous skeleton. Fins at different locations of the fish body serve different purposes, and are divided into two groups:
858-413: Is a demersal fish , not a flying fish, and uses its pelvic fins to walk along the bottom of the ocean. Fins can have an adaptive significance as sexual ornaments. During courtship, the female cichlid , Pelvicachromis taeniatus , displays a large and visually arresting purple pelvic fin . "The researchers found that males clearly preferred females with a larger pelvic fin and that pelvic fins grew in
924-981: Is a great fish for any tank type; even the hardier species of Apistogramma and similar dwarf cichlids make good companions, with water parameters compromising between the splitfins' and the cichlids' requirements at a point similar to most tap water . A. splendens thrives best in clean, well-aerated water, at temperatures around 70-75 °F (20-25 °C) and neutral or slightly higher pH , with water hardness between 5 and 10 dGH composed mainly from calcium hardness. They do not tolerate overly low pH and too soft water, and are unsuitable for dedicated rainforest aquaria with low pH and almost-zero hardness (e.g. for most tetras or danionins ). Butterfly splitfins are strong swimmers and social fish; they dwell in groups of three to five males and three to seven females in large tanks where they can grow to full size. In small tanks, they stay small, and fewer individuals or no other fish should be kept. Their overall effect on plant growth
990-463: Is beneficial as they keep down algae and clean off detritus . A. splendens breeds quite readily in the aquarium; some floating plants such as Ceratopteris or Ceratophyllum provide protection for young fry . Aggressiveness varies with population density ; at high population densities, tank decoration is highly significant in influencing behavior. At least among captive populations, butterfly splitfins become more aggressive if much decoration
1056-453: Is different from Wikidata All article disambiguation pages All disambiguation pages Ameca (fish) The butterfly splitfin or butterfly goodeid ( Ameca splendens ) is a bony fish from the monotypic genus Ameca of the splitfin family ( Goodeidae ). It was formerly found throughout the Ameca River drainage in Mexico; the type locality is Rio Teuchitlán in
1122-411: Is largely limited to algae and Ceratophyllum hornworts. The remnant wild population coexists with the native blackfin goodea ( Goodea atripinnis ) and Lerma live-bearer ( Poeciliopsis infans ), as well as with the common molly ( Poecilia sphenops ), Oreochromis tilapias , and the bluegill ( Lepomis macrochirus ) which presumably have all been introduced. Among groups of A. splendens ,
1188-512: Is more closely related to the butterfly splitfin than it is to other species currently placed in the genus Xenotaca . In its former natural habitat, the bedrock is limestone , resulting in a hard and alkaline water with a general hardness of 6-10 dGH , while the temporary (carbonate) hardness is usually between 7 and 11°. The pH is around 8, and temperature varies little between the seasons, but ranges between about 70 and 85 °F (20 and 30 °C) between day and night. The vegetation
1254-524: Is ochre, with silvery sides and a brownish back, which in males usually have numerous glittering metallic scales. Females and immatures having black dots on the sides and ochre fins. The fins of males intensify in color when they are excited, and depending on their mood, they can show more or less strongly a black band along the side. For the first two weeks or so after birth, the young are entirely silvery. Males can also be told apart from females because their anal fin 's front part splits off and transforms to
1320-614: Is one type of living lobe-finned fish. Both extant members of this group, the West Indian Ocean coelacanth ( Latimeria chalumnae ) and the Indonesian coelacanth ( Latimeria menadoensis ), are found in the genus Latimeria . Coelacanths are thought to have evolved roughly into their current form about 408 million years ago, during the early Devonian. Locomotion of the coelacanths is unique to their kind. To move around, coelacanths most commonly take advantage of up or downwellings of
1386-418: Is placed in the tank. Butterfly splitfins are voracious, and eat most forms of commercial fish food . They take live prey up to the size of week-old guppy fry, but need plant material, ideally green algae, to thrive. They are ideal algae eaters for tanks with small, hard-water cichlids . If not enough algae are available, vegetables such as lettuce , spinach , or green peas are recommended additions to
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#17328521114031452-436: Is prohibited in many countries. Foil shaped fins generate thrust when moved, the lift of the fin sets water or air in motion and pushes the fin in the opposite direction. Aquatic animals get significant thrust by moving fins back and forth in water. Often the tail fin is used, but some aquatic animals generate thrust from pectoral fins . Cavitation occurs when negative pressure causes bubbles (cavities) to form in
1518-432: Is relatively conservative in lobe-finned fishes. However, there are a few examples from the fossil record that show aberrant morphologies , such as Allenypterus , Rebellatrix , Foreyia or the tetrapodomorphs . Ray-finned fishes form a class of bony fishes called Actinopterygii. Their fins contain spines or rays. A fin may contain only spiny rays, only soft rays, or a combination of both. If both are present,
1584-402: Is something of a mystery. It is frequently clipped off to mark hatchery-raised fish, though data from 2005 showed that trout with their adipose fin removed have an 8% higher tailbeat frequency. Additional information released in 2011 has suggested that the fin may be vital for the detection of, and response to, stimuli such as touch, sound and changes in pressure. Canadian researchers identified
1650-487: Is the characiform-type way, where the adipose fin develops late after the larval-fin fold has diminished and the other median fins have developed. They claim the existence of the characiform-type of development suggests the adipose fin is not "just a larval fin fold remainder" and is inconsistent with the view that the adipose fin lacks function. Research published in 2014 indicates that the adipose fin has evolved repeatedly in separate lineages . (A) - Heterocercal means
1716-433: Is the heterocercal tail, which aids in locomotion. Most sharks have eight fins. Sharks can only drift away from objects directly in front of them because their fins do not allow them to move in the tail-first direction. Unlike modern cartilaginous fish, members of stem chondrichthyan lineages (e.g. the † climatiids and the † diplacanthids ) possessed pectoral dermal plates as well as dermal spines associated with
1782-400: Is the largest class of vertebrates in existence today, making up more than 50% of species. In the distant past, lobe-finned fish were abundant; however, there are currently only 8 species. Bony fish have fin spines called lepidotrichia or "rays" (due to how the spines spread open). They typically have swim bladders , which allow the fish to alter the relative density of its body and thus
1848-587: Is thought that their rostral organ helps give the coelacanth electroperception, which aids in their movement around obstacles. Lungfish are also living lobe-finned fish. They occur in Africa ( Protopterus ), Australia ( Neoceratodus ), and South America ( Lepidosiren ). Lungfish evolved during the Devonian Period. Genetic studies and paleontological data confirm that lungfish are the closest living relatives of land vertebrates . Fin arrangement and body shape
1914-572: The Humane Society International , approximately 100 million sharks are killed each year for their fins, in an act known as shark finning . After the fins are cut off, the mutilated sharks are thrown back in the water and left to die. In some countries of Asia , shark fins are a culinary delicacy, such as shark fin soup . Currently, international concerns over the sustainability and welfare of sharks have impacted consumption and availability of shark fin soup worldwide. Shark finning
1980-477: The Middle Triassic † Saurichthys , the oldest known example of viviparity in a ray-finned fish. Claspers are found on the males of cartilaginous fishes . They are the posterior part of the pelvic fins that have also been modified to function as intromittent organs, and are used to channel semen into the female's cloaca during copulation. The act of mating in sharks usually includes raising one of
2046-417: The buoyancy , so it can sink or float without having to use the fins to swim up and down. However, swim bladders are absent in many fish, most notably in lungfishes , who have evolved their swim bladders into primitive lungs , which may have a shared evolutionary origin with those of their terrestrial relatives, the tetrapods . Bony fishes also have a pair of opercula that function to draw water across
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2112-409: The extinct † Petalodontiformes (e.g. † Belantsea , † Janassa , † Menaspis ), which belong to Holocephali (ratfish and their fossil relatives), or in † Aquilolamna ( Selachimorpha ) and † Squatinactis (Squatinactiformes). Some cartilaginous fishes have an eel-like locomotion (e.g. Chlamydoselachus , † Thrinacoselache , † Phoebodus ) According to
2178-426: The gills , which help them breathe without needing to swim forward to force the water into the mouth across the gills. Lobe-finned fishes form a class of bony fishes called Sarcopterygii. They have fleshy, lobed , paired fins, which are joined to the body by a series of bones. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobe-like, scaly stalk extending from
2244-831: The midsagittal unpaired fins and the more laterally located paired fins . Unpaired fins are predominantly associated with generating linear acceleration via oscillating propulsion , as well as providing directional stability ; while paired fins are used for generating paddling acceleration , deceleration, and differential thrust or lift for turning , surfacing or diving and rolling . Fins can also be used for other locomotions other than swimming, for example, flying fish use pectoral fins for gliding flight above water surface, and frogfish and many amphibious fishes use pectoral and/or pelvic fins for crawling . Fins can also be used for other purposes: remoras and gobies have evolved sucker -like dorsal fins for attaching to surfaces and "hitchhiking"; male sharks and mosquitofish use
2310-471: The ventral portion. This is because the shark's vertebral column extends into that dorsal portion, providing a greater surface area for muscle attachment. This allows more efficient locomotion among these negatively buoyant cartilaginous fish. By contrast, most bony fish possess a homocercal caudal fin. Tiger sharks have a large upper lobe , which allows for slow cruising and sudden bursts of speed. The tiger shark must be able to twist and turn in
2376-637: The State of México, often informally abbreviated to "Ameca" Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Ameca . If an internal link led you here, you may wish to change the link to point directly to the intended article. Humanoid Robot [ edit ] Ameca (robot) Retrieved from " https://en.wikipedia.org/w/index.php?title=Ameca&oldid=1131097289 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Short description
2442-434: The ability to lock their spines outwards. Triggerfish also use spines to lock themselves in crevices to prevent them being pulled out. Lepidotrichia are usually composed of bone , but those of early osteichthyans - such as Cheirolepis - also had dentine and enamel . They are segmented and appear as a series of disks stacked one on top of another. They may have been derived from dermal scales. The genetic basis for
2508-514: The body. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates ( amphibians ) in the Devonian Period . Sarcopterygians also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of most ray-finned fish (except some teleosts ). The caudal fin is either heterocercal (only fossil taxa ) or diphycercal. The coelacanth
2574-548: The claspers to allow water into a siphon through a specific orifice . The clasper is then inserted into the cloaca, where it opens like an umbrella to anchor its position. The siphon then begins to contract expelling water and sperm. Other uses of fins include walking and perching on the sea floor, gliding over water, cooling of body temperature, stunning of prey, display (scaring of predators, courtship), defence (venomous fin spines, locking between corals), luring of prey, and attachment structures. The Indo-Pacific sailfish has
2640-465: The current and drift. They use their paired fins to stabilize their movement through the water. While on the ocean floor their paired fins are not used for any kind of movement. Coelacanths can create thrust for quick starts by using their caudal fins. Due to the high number of fins they possess, coelacanths have high maneuverability and can orient their bodies in almost any direction in the water. They have been seen doing headstands and swimming belly up. It
2706-526: The diet. Fry do not need "baby" food such as brine shrimp or nauplia , though as in adults, plant food increase growth and vitality. Lighting should be strong, to encourage growth of algae; direct sunlight is ideal. In summer, they can be kept in outside tanks, basins, or small ponds in temperate and warmer areas; they can tolerate overnight air temperatures of 60 °F (15 °C) well enough, but should be protected from birds, cats, and other predators . Many zoos and public aquariums maintain colonies of
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2772-738: The dorsal surface and no dorsal fin). In some fish such as tuna or sauries , they are rayless, non-retractable, and found between the last dorsal and/or anal fin and the caudal fin. Bony fishes ( Actinopterygii and Sarcopterygii ) form a taxonomic group called Osteichthyes (or Euteleostomi , which includes also land vertebrates ); they have skeletons made of bone mostly, and can be contrasted with cartilaginous fishes (see below), which have skeletons made mainly of cartilage (except for their teeth , fin spines , and denticles ). Bony fishes are divided into ray-finned and lobe-finned fish . Most living fish are ray-finned, an extremely diverse and abundant group consisting of over 30,000 species . It
2838-525: The dorsal, anal and caudal fins are unpaired and situated along the midline of the body. For every type of fin, there are a number of fish species in which this particular fin has been lost during evolution (e.g. pelvic fins in † Bobasatrania , caudal fin in ocean sunfish ). In some clades , additional unpaired fins were acquired during evolution (e.g. additional dorsal fins, adipose fin). In some † Acanthodii ("spiny sharks"), one or more pairs of "intermediate" or "prepelvic" spines are present between
2904-442: The female. The male shortly inserts the organ into the sex opening of the female, with hook-like adaptations that allow the fish to grip onto the female to ensure impregnation. If a female remains stationary and her partner contacts her vent with his gonopodium, she is fertilized. The sperm is preserved in the female's oviduct. This allows females to fertilize themselves at any time without further assistance from males. In some species,
2970-400: The first dorsal fin spine was modified, forming a spine-brush complex. As with most fish, the tails of sharks provide thrust, making speed and acceleration dependent on tail shape. Caudal fin shapes vary considerably between shark species, due to their evolution in separate environments. Sharks possess a heterocercal caudal fin in which the dorsal portion is usually noticeably larger than
3036-501: The formation of a linked chain of vortex rings" and that "the dorsal and anal fin wakes are rapidly entrained by the caudal fin wake, approximately within the timeframe of a subsequent tail beat". Once motion has been established, the motion itself can be controlled with the use of other fins. The bodies of reef fishes are often shaped differently from open water fishes . Open water fishes are usually built for speed, streamlined like torpedoes to minimise friction as they move through
3102-553: The formation of the fin rays is thought to be genes coded for the production of certain proteins. It has been suggested that the evolution of the tetrapod limb from lobe-finned fishes is related to the loss of these proteins. Cartilaginous fishes form a class of fishes called Chondrichthyes. They have skeletons made of cartilage rather than bone . The class includes sharks , rays and chimaeras . Shark fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling
3168-510: The gonopodium may be half the total body length. Occasionally the fin is too long to be used, as in the "lyretail" breeds of Xiphophorus helleri . Hormone treated females may develop gonopodia. These are useless for breeding. Similar organs with similar characteristics are found in other fishes, for example the andropodium in the Hemirhamphodon or in the Goodeidae or the gonopodium in
3234-410: The horny keratin in hair and feathers. Originally the pectoral and pelvic girdles, which do not contain any dermal elements, did not connect. In later forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and puboischiadic bars evolved. In rays , the pectoral fins have connected to the head and are very flexible. One of the primary characteristics present in most sharks
3300-443: The lateral fin-fold theory, first suggested in 1877, which proposes that paired fins budded from longitudinal, lateral folds along the epidermis just behind the gills. There is weak support for both hypotheses in the fossil record and in embryology. However, recent insights from developmental patterning have prompted reconsideration of both theories in order to better elucidate the origins of paired fins. Carl Gegenbaur 's concept of
3366-556: The male sometimes rotates to present either flank to the female. The females respond by shaking their heads. The fry when born can be up to 0.8 in (20 mm) in length, as the females feed the unborn young via trophotaenia which have a similar function as the umbilical cord in humans . The butterfly splitfin has a reputation of being a fin nipper, but being a large and robust fish, it will certainly bully small and delicate species like guppies or small tetras . When housed with less tender species that require similar conditions, it
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#17328521114033432-493: The males of some species in the Anablepidae and Poeciliidae families. They are anal fins that have been modified to function as movable intromittent organs and are used to impregnate females with milt during mating. The third, fourth and fifth rays of the male's anal fin are formed into a tube-like structure in which the sperm of the fish is ejected. When ready for mating, the gonopodium becomes erect and points forward towards
3498-458: The margin at the rear of their bodies is a line of small rayless, non-retractable fins, known as finlets . There has been much speculation about the function of these finlets. Research done in 2000 and 2001 by Nauen and Lauder indicated that "the finlets have a hydrodynamic effect on local flow during steady swimming" and that "the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by
3564-690: The paired fins. The oldest species demonstrating these features is the † acanthodian † Fanjingshania renovata from the lower Silurian ( Aeronian ) of China. Fanjingshania possess compound pectoral plates composed of dermal scales fused to a bony plate and fin spines formed entirely of bone. Fin spines associated with the dorsal fins are rare among extant cartilaginous fishes, but are present, for instance, in Heterodontus or Squalus . Dorsal fin spines are typically developed in many fossil groups, such as in † Hybodontiformes , † Ctenacanthiformes or † Xenacanthida . In † Stethacanthus ,
3630-403: The pectoral and pelvic fins, but these are not associated with fins. The pelvic fin assists the fish in going up or down through the water, turning sharply, and stopping quickly. The dorsal fins are located on the back. A fish can have up to three dorsal fins. The dorsal fins serve to protect the fish against rolling, and assist it in sudden turns and stops. The function of the adipose fin
3696-551: The species. Anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim . Apart from the tail or caudal fin , fish fins have no direct connection with the back bone and are supported only by muscles . Fish fins are distinctive anatomical features with varying structures among different clades : in ray-finned fish ( Actinopterygii ), fins are mainly composed of bony spines or rays covered by
3762-402: The spiny rays are always anterior . Spines are generally stiff and sharp. Rays are generally soft, flexible, segmented, and may be branched. This segmentation of rays is the main difference that separates them from spines; spines may be flexible in certain species, but they will never be segmented. Spines have a variety of uses. In catfish , they are used as a form of defense; many catfish have
3828-552: The tail of swimming mackerel". Fish use multiple fins, so it is possible that a given fin can have a hydrodynamic interaction with another fin. In particular, the fins immediately upstream of the caudal (tail) fin may be proximate fins that can directly affect the flow dynamics at the caudal fin. In 2011, researchers using volumetric imaging techniques were able to generate "the first instantaneous three-dimensional views of wake structures as they are produced by freely swimming fishes". They found that "continuous tail beats resulted in
3894-450: The tip of the tail and the tail is symmetrical but not expanded (as in the first fishes and the cyclostomes , and a more primitive precursor in lancelets ) (C) - Homocercal where the fin usually appears superficially symmetric but in fact the vertebrae extend for a very short distance into the upper lobe of the fin. Homocercal caudal fins can, however, also appear asymmetric (e.g. blue flying fish ). Most modern fishes ( teleosts ) have
3960-419: The vertebrae extend into the upper lobe of the tail, often making it longer than the lower lobe (as in sharks , † Placodermi , most stem Actinopterygii , and sturgeons and paddlefish ). However, the external shape of heterocercal tail fins can also appear symmetric (e.g. † Birgeria , † Bobasatrania ). Heterocercal is the opposite of hypocercal (B) - Protocercal means the vertebrae extend to
4026-639: The vicinity of Teuchitlán , Jalisco . The species was only ever found in an area about 10 miles (15 km) in diameter. Today, the species is rated as critically endangered by the IUCN . A remnant population has been found to persist in El Rincón waterpark near the town of Ameca . Possibly, it also exists in a feral state in the United States; individuals apparently derived from escaped or introduced captive stock were met with in southeastern Nevada , but this
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#17328521114034092-511: The water easily when hunting to support its varied diet, whereas the porbeagle shark , which hunts schooling fish such as mackerel and herring , has a large lower lobe to help it keep pace with its fast-swimming prey. Other tail adaptations help sharks catch prey more directly, such as the thresher shark 's usage of its powerful, elongated upper lobe to stun fish and squid. On the other hand, rays rely on their enlarged pectoral fins for propulsion. Similarly enlarged pectoral fins can be found in
4158-412: The water temperature and the condition of the fish. Mating is preceded by a courtship, where the males present themselves to the females with their heads pointing downwards – up to 45° from horizontal – and shake the forward part of their bodies. In that respect, they resemble the jeweled splitfin ( Xenotoca variata ); they do not have a ritualized "courtship dance" as some other splitfins, but
4224-697: The water. Reef fish operate in the relatively confined spaces and complex underwater landscapes of coral reefs . For this manoeuvrability is more important than straight line speed, so coral reef fish have developed bodies which optimize their ability to dart and change direction. They outwit predators by dodging into fissures in the reef or playing hide and seek around coral heads. The pectoral and pelvic fins of many reef fish, such as butterflyfish , damselfish and angelfish , have evolved so they can act as brakes and allow complex manoeuvres. Many reef fish, such as butterflyfish , damselfish and angelfish , have evolved bodies which are deep and laterally compressed like
4290-522: The “Archipterygium” was introduced in 1876. It was described as a gill ray, or "joined cartilaginous stem," that extended from the gill arch. Additional rays arose from along the arch and from the central gill ray. Gegenbaur suggested a model of transformative homology – that all vertebrate paired fins and limbs were transformations of the Archipterygium. Based on this theory, paired appendages such as pectoral and pelvic fins would have differentiated from
4356-412: Was over forty years ago. For some time, it was a popular fish among aquarists , but hobbyist stocks have declined recently, placing its survival in jeopardy. As its common name implies, it is indeed quite an attractive fish. A dominant mature male specimen a large dorsal fin which like the caudal fin is washed with black. A yellow band stretches along the caudal's back margin. The body of both sexes
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