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92-491: Tiburon (Spanish Tiburón , " shark ") may refer to: Shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton , five to seven gill slits on the sides of the head , and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii ) and are the sister group to the Batoidea ( rays and kin). Some sources extend

184-426: A heterocercal caudal fin in which the dorsal portion is usually noticeably larger than 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

276-415: A cell similar to hair cells present in the vertebrate ear that interact with the surrounding aquatic environment. This helps sharks distinguish between the currents around them, obstacles off on their periphery, and struggling prey out of visual view. The shark can sense frequencies in the range of 25 to 50  Hz . Shark lifespans vary by species. Most live 20 to 30 years. The spiny dogfish has one of

368-418: A constant supply of oxygenated water. A small number of species have lost the ability to pump water through their gills and must swim without rest. These species are obligate ram ventilators and would presumably asphyxiate if unable to move. Obligate ram ventilation is also true of some pelagic bony fish species. The respiratory and circulatory process begins when deoxygenated venous blood travels to

460-499: A few known exceptions, such as the bull shark and the river sharks , which can be found in both seawater and freshwater, and the Ganges shark , which lives only in freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics . They have numerous sets of replaceable teeth. Several species are apex predators , which are organisms that are at

552-423: 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 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

644-438: A long surface area, requiring food to circulate inside the short gut until fully digested, when remaining waste products pass into the cloaca . A few sharks appear fluorescent under blue light, such as the swell shark and the chain catshark , where the fluorophore derives from a metabolite of kynurenic acid . Sharks have keen olfactory senses, located in the short duct (which is not fused, unlike bony fish) between

736-727: A relatively shallow sea compared to other bodies of water. The pressure of the South American Plate to the east of the Caribbean causes the region of the Lesser Antilles to have high volcanic activity. A very serious eruption of Mount Pelée in 1902 caused many casualties. The Caribbean sea floor is also home to two oceanic trenches : the Cayman Trench and the Puerto Rico Trench , which put

828-445: A row behind the head. A modified slit called a spiracle lies just behind the eye, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks. Spiracles are reduced or missing in active pelagic sharks. While the shark is moving, water passes through the mouth and over the gills in a process known as "ram ventilation". While at rest, most sharks pump water over their gills to ensure

920-405: A similar mechanism for maintaining an elevated body temperature. Larger species, like the whale shark, are able to conserve their body heat through sheer size when they dive to colder depths, and the scalloped hammerhead close its mouth and gills when they dives to depths of around 800 metres, holding its breath till it reach warmer waters again. In contrast to bony fish, with the exception of

1012-555: A single type of cone photoreceptor sensitive to green and, seeing only in shades of grey and green, are believed to be effectively colorblind. The study indicates that an object's contrast against the background, rather than colour, may be more important for object detection. Although it is hard to test the hearing of sharks, they may have a sharp sense of hearing and can possibly hear prey from many miles away. The hearing sensitivity for most shark species lies between 20 and 1000 Hz. A small opening on each side of their heads (not

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1104-473: A small number of well-developed young as opposed to a large number of poorly developed young. Fecundity in sharks ranges from 2 to over 100 young per reproductive cycle. Sharks mature slowly relative to many other fish. For example, lemon sharks reach sexual maturity at around age 13–15. Caribbean Sea The Caribbean Sea is one of the largest seas on Earth and has an area of about 2,754,000 km (1,063,000 sq mi). The sea's deepest point

1196-400: A tissue called tapetum lucidum . This tissue is behind the retina and reflects light back to it, thereby increasing visibility in the dark waters. The effectiveness of the tissue varies, with some sharks having stronger nocturnal adaptations. Many sharks can contract and dilate their pupils , like humans, something no teleost fish can do. Sharks have eyelids, but they do not blink because

1288-621: A year visit the area, including (in 1991–1992) about 8 million cruise ship tourists. Tourism based upon scuba diving and snorkeling on coral reefs of many Caribbean islands makes a major contribution to their economies. These three form the SSS islands that with the ABC islands comprise the Dutch Caribbean , of which the BES islands are not direct Kingdom constituents but subsumed with

1380-478: Is called coral bleaching , and can lead to the devastation of large areas of reef. Over 42% of corals are completely bleached, and 95% are experiencing some type of whitening. Historically the Caribbean is thought to contain 14% of the world's coral reefs. The habitats supported by the reefs are critical to such tourist activities as fishing and diving , and provide an annual economic value to Caribbean nations of US$ 3.1–4.6 billion. Continued destruction of

1472-707: Is concentrated around coral reefs where there is little variation in water temperature, purity and salinity. Leeward side of lagoons provide areas of growth for sea grasses . Turtle grass ( Thalassia testudinum ) is common in the Caribbean as is manatee grass ( Syringodium filiforme ) which can grow together as well as in fields of single species at depths up to 20 m (66 ft). Another type shoal grass ( Halodule wrightii ) grows on sand and mud surfaces at depths of up to 5 m (16 ft). In brackish water of harbours and estuaries at depths less than 2.5 m (8 ft 2 in) widgeongrass ( Ruppia maritima ) grows. Representatives of three species belonging to

1564-648: Is debated. Some believe that electro- and chemoreception are more significant, while others point to the nictating membrane as evidence that sight is important, since presumably the shark would not protect its eyes were they unimportant. The use of sight probably varies with species and water conditions. The shark's field of vision can swap between monocular and stereoscopic at any time. A micro-spectrophotometry study of 17 species of sharks found 10 had only rod photoreceptors and no cone cells in their retinas giving them good night vision while making them colorblind . The remaining seven species had in addition to rods

1656-676: Is divided into the superorders Galea (or Galeomorphii ), and Squalea (or Squalomorphii ). The Galeans are the Heterodontiformes , Orectolobiformes , Lamniformes , and Carcharhiniformes . Lamnoids and Carcharhinoids are usually placed in one clade , but recent studies show that Lamnoids and Orectoloboids are a clade. Some scientists now think that Heterodontoids may be Squalean. The Squaleans are divided into Hexanchiformes and Squalomorpha. The former includes cow shark and frilled shark , though some authors propose that both families be moved to separate orders. The Squalomorpha contains

1748-411: Is endangered. The Antilles along with Central America lie in the flight path of migrating birds from North America so the size of populations is subject to seasonal fluctuations. Parrots and bananaquits are found in forests. Over the open sea can be seen frigatebirds and tropicbirds . The Caribbean region has seen a significant increase in human activity since the colonization period. The sea

1840-484: Is endangered. The rhinoceros iguana from the island of Hispaniola which is shared between Haiti and the Dominican Republic is also endangered. The region has several types of sea turtle ( loggerhead , green turtle , hawksbill , leatherback turtle , Atlantic ridley and olive ridley ). Some species are threatened with extinction. Their populations have been greatly reduced since the 17th century –

1932-409: Is high, species of sharks from the family Carcharhinidae have smaller olfactory bulbs. Sharks found in deeper waters also have larger olfactory bulbs. Sharks have the ability to determine the direction of a given scent based on the timing of scent detection in each nostril. This is similar to the method mammals use to determine direction of sound. They are more attracted to the chemicals found in

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2024-581: Is limited, so sharks employ dynamic lift to maintain depth while swimming. Sand tiger sharks store air in their stomachs, using it as a form of swim bladder. Bottom-dwelling sharks, like the nurse shark , have negative buoyancy, allowing them to rest on the ocean floor. Some sharks, if inverted or stroked on the nose, enter a natural state of tonic immobility . Researchers use this condition to handle sharks safely. Like other fish, sharks extract oxygen from seawater as it passes over their gills . Unlike other fish, shark gill slits are not covered, but lie in

2116-434: Is observed in the cookiecutter shark . Tooth shape depends on the shark's diet: those that feed on mollusks and crustaceans have dense and flattened teeth used for crushing, those that feed on fish have needle-like teeth for gripping, and those that feed on larger prey such as mammals have pointed lower teeth for gripping and triangular upper teeth with serrated edges for cutting. The teeth of plankton-feeders such as

2208-445: Is one of the largest oil production areas in the world, producing approximately 170 million tons per year. The area also generates a large fishing industry for the surrounding countries, accounting for 500,000 tonnes (490,000 long tons; 550,000 short tons) of fish a year. Human activity in the area also accounts for a significant amount of pollution . The Pan American Health Organization estimated in 1993 that only about 10% of

2300-496: Is still evidential in several species termed " dogfish ," or the porbeagle . The etymology of the word shark is uncertain. The most likely etymology states that the original sense of the word was that of "predator, one who preys on others" from the Dutch schurk , meaning 'villain, scoundrel' ( cf. card shark , loan shark , etc.), which was later applied to the fish due to its predatory behaviour. A now disproven theory

2392-775: Is that it derives from the Yucatec Maya word xook ( pronounced [ʃoːk] ), meaning 'shark'. Evidence for this etymology came from the Oxford English Dictionary , which notes that shark first came into use after Sir John Hawkins ' sailors exhibited one in London in 1569 and posted " sharke " to refer to the large sharks of the Caribbean Sea . However, the Middle English Dictionary records an isolated occurrence of

2484-710: Is the Cayman Trough , between the Cayman Islands and Jamaica , at 7,686 m (25,217 ft) below sea level . The Caribbean coastline has many gulfs and bays : the Gulf of Gonâve , the Gulf of Venezuela , the Gulf of Darién , Golfo de los Mosquitos , the Gulf of Paria and the Gulf of Honduras . The Caribbean Sea has the world's second-largest barrier reef , the Mesoamerican Barrier Reef . It runs 1,000 km (620 mi) along

2576-694: Is the national flower of Jamaica and the Bayahibe rose ( Pereskia quisqueyana ) which is the national flower of the Dominican Republic and the ceiba which is the national tree of both Puerto Rico and Guatemala . The mahogany is the national tree of the Dominican Republic and Belize . The caimito ( Chrysophyllum cainito ) grows throughout the Caribbean. In coastal zones there are coconut palms and in lagoons and estuaries are found thick areas of black mangrove and red mangrove ( Rhizophora mangle ). In shallow water flora and fauna

2668-463: Is the second most polluted sea. Pollution (in the form of up to 300,000 tonnes of solid garbage dumped into the Caribbean Sea each year) is progressively endangering marine ecosystems, wiping out species, and harming the livelihoods of the local people, which is primarily reliant on tourism and fishing. KfW took part in a €25.7 million funding agreement to eliminate marine trash and boost

2760-478: The Caribbean ; only one extant species is not endangered. There are 500 species of reptiles (94% of which are endemic ). Islands are inhabited by some endemic species such as rock iguanas and American crocodile . The blue iguana , endemic to the island of Grand Cayman , is endangered. The green iguana is invasive to Grand Cayman . The Mona ground iguana which inhabits the island of Mona, Puerto Rico ,

2852-687: The Devonian . Anachronistidae , the oldest probable representatives of Neoselachii, the group containing modern sharks (Selachimorpha) and rays (Batoidea) to the exclusion of most extinct elasmobranch groups, date to the Carboniferous . Selachiimorpha and Batoidea are suggested by some to have diverged during the Triassic . Fossils of the earliest true sharks may have appeared during the Permian , based on remains of " synechodontiforms " found in

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2944-504: The Dutch Republic , France , Courland and Denmark ). Following the colonization of the Caribbean islands, the Caribbean Sea became a busy area for European-based marine trading and transports. This commerce eventually attracted pirates such as Samuel Bellamy and Blackbeard . As of 2015 the area is home to 22 island territories and borders 12 continental countries . The International Hydrographic Organization defines

3036-681: The Early Jurassic around 200  million years ago , with the oldest known member being Agaleus , though records of true sharks may extend back as far as the Permian . Sharks range in size from the small dwarf lanternshark ( Etmopterus perryi ), a deep sea species that is only 17 centimetres (6.7 in) in length, to the whale shark ( Rhincodon typus ), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. They are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are

3128-584: The Sea of the Antilles became a common alternative name for the "Caribbean Sea" in various European languages. Spanish dominance in the region remained undisputed during the first century of European colonization. From the 16th century, Europeans visiting the Caribbean region distinguished the "South Sea" (the Pacific Ocean south of the isthmus of Panama) from the "North Sea" (the Caribbean Sea north of

3220-737: The Squaliformes and the Hypnosqualea. The Hypnosqualea may be invalid. It includes the Squatiniformes , and the Pristorajea, which may also be invalid, but includes the Pristiophoriformes and the Batoidea . There are more than 500 species of sharks split across thirteen orders , including several orders of sharks that have gone extinct: Shark teeth are embedded in the gums rather than directly affixed to

3312-849: The Virgin Islands to north of Trinidad and Tobago , which is in the Atlantic. This arc was formed by the collision of the South American Plate with the Caribbean Plate . It included active and extinct volcanoes such as Mount Pelee , the Quill on Sint Eustatius in the Caribbean Netherlands , La Soufrière in Saint Vincent and the Grenadines and Morne Trois Pitons on Dominica . The larger islands in

3404-463: The bull shark , which has developed a way to change its kidney function to excrete large amounts of urea. When a shark dies, the urea is broken down to ammonia by bacteria, causing the dead body to gradually smell strongly of ammonia. Research in 1930 by Homer W. Smith showed that sharks' urine does not contain sufficient sodium to avoid hypernatremia , and it was postulated that there must be an additional mechanism for salt secretion. In 1960 it

3496-501: The circular economy in the Caribbean's Small Island Developing States . The project "Sustainable finance methods for marine preservation in the Caribbean" will assist remove solid waste and keep it out of the marine and coastal environment by establishing a new facility under the Caribbean Biodiversity Fund (CBF). Non-governmental organizations, universities, public institutions, civil society organizations, and

3588-511: The clade Selachimorpha in the subclass Elasmobranchii in the class Chondrichthyes . The Elasmobranchii also include rays and skates ; the Chondrichthyes also include Chimaeras . It was thought that the sharks form a polyphyletic group: some sharks are more closely related to rays than they are to some other sharks, but current molecular studies support monophyly of both groups of sharks and batoids. The clade Selachimorpha

3680-441: The coelacanth , the blood and other tissue of sharks and Chondrichthyes is generally isotonic to their marine environments because of the high concentration of urea (up to 2.5% ) and trimethylamine N-oxide (TMAO), allowing them to be in osmotic balance with the seawater. This adaptation prevents most sharks from surviving in freshwater, and they are therefore confined to marine environments. A few exceptions exist, such as

3772-461: The cranium . The jaw's surface (in comparison to the shark's vertebrae and gill arches) needs extra support due to its heavy exposure to physical stress and its need for strength. It has a layer of tiny hexagonal plates called " tesserae ", which are crystal blocks of calcium salts arranged as a mosaic. This gives these areas much of the same strength found in the bony tissue found in other animals. Generally sharks have only one layer of tesserae, but

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3864-456: The electric fields they produce. Ocean currents moving in the magnetic field of the Earth also generate electric fields that sharks can use for orientation and possibly navigation. This system is found in most fish, including sharks. It is a tactile sensory system which allows the organism to detect water speed and pressure changes near by. The main component of the system is the neuromast,

3956-414: The great white shark ) are homeothermic and maintain a higher body temperature than the surrounding water. In these sharks, a strip of aerobic red muscle located near the center of the body generates the heat, which the body retains via a countercurrent exchange mechanism by a system of blood vessels called the rete mirabile ("miraculous net"). The common thresher and bigeye thresher sharks have

4048-901: The Caribbean Islands and the Central American coast. Among them stands out the Belize Barrier Reef , with an area of 963 km (372 sq mi), which was declared a World Heritage Site in 1996. It forms part of the Great Mayan Reef (also known as the MBRS ) and, being over 1,000 km (600 mi) in length, is the world's second longest. It runs along the Caribbean coasts of Mexico , Belize , Guatemala and Honduras . Since 2005 unusually warm Caribbean waters have been increasingly threatening Caribbean coral reefs . Coral reefs support some of

4140-746: The Caribbean became separated from the Gulf of Mexico and the Atlantic Ocean by the land of Cuba and Haiti . The Caribbean remained like this for most of the Cenozoic until the Holocene when rising water levels of the oceans restored communication with the Atlantic Ocean. The Caribbean's floor is composed of sub-oceanic sediments of deep red clay in the deep basins and troughs. On continental slopes and ridges calcareous silts are found. Clay minerals have likely been deposited by

4232-531: The Caribbean itself. The Caribbean hurricane season as a whole lasts from June through November, with the majority of hurricanes occurring during August and September. On average around nine tropical storms form each year, with five reaching hurricane strength. According to the National Hurricane Center 385 hurricanes occurred in the Caribbean between 1494 and 1900. The region has a high level of biodiversity and many species are endemic to

4324-1053: The Caribbean marine life, such as Caribbean Conservation Corporation which seeks to study and protect sea turtles while educating others about them. In connection with the foregoing, the Institute of Marine Sciences and Limnology of the National Autonomous University of Mexico , conducted a regional study, funded by the Department of Technical Cooperation of the International Atomic Energy Agency , in which specialists from 11 Latin American countries (Colombia, Costa Rica, Cuba, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Panama, Dominican Republic, Venezuela) plus Jamaica participated. The findings indicate that heavy metals such as mercury, arsenic, and lead, have been identified in

4416-412: The Caribbean there is industrial catching of lobster and sardines (off the coast of Yucatán Peninsula ). There are 90 species of mammals in the Caribbean including sperm whales , humpback whales and dolphins . The island of Jamaica is home to seals and manatees . The Caribbean monk seal which lived in the Caribbean is considered extinct. Solenodons and hutias are mammals found only in

4508-541: The Caribbean through the Anegada Passage between the Lesser Antilles and the Virgin Islands and the Windward Passage between Cuba and Haiti . The Yucatán Channel between Mexico and Cuba links the Gulf of Mexico with the Caribbean. The deepest points of the sea lie in Cayman Trough with depths reaching approximately 7,686 m (25,220 ft). Despite this, the Caribbean Sea is considered

4600-666: The Caribbean, 600 species of birds have been recorded, of which 163 are endemic such as todies , Fernandina's flicker and palmchat . The American yellow warbler is found in many areas, as is the green heron . Of the endemic species 48 are threatened with extinction including the Puerto Rican amazon , and the Zapata wren . According to Birdlife International in 2006 in Cuba 29 species of bird are in danger of extinction and two species officially extinct. The black-fronted piping guan

4692-417: The Caribbean. The vegetation of the region is mostly tropical but differences in topography , soil and climatic conditions increase species diversity . Where there are porous limestone terraced islands these are generally poor in nutrients. It is estimated that 13,000 species of plants grow in the Caribbean of which 6,500 are endemic . For example, guaiac wood ( Guaiacum officinale ), the flower of which

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4784-1065: The Early Permian of Russia, but if remains of "synechodontiformes" from the Permian and Triassic are true sharks, they only had low diversity. Modern shark orders first appeared during the Early Jurassic, and during the Jurassic true sharks underwent great diversification. Selachimorphs largely replaced the hybodonts , which had previously been a dominant group of shark-like fish during the Triassic and Early Jurassic. Batoidea [REDACTED] Heterodontiformes [REDACTED] Orectolobiformes [REDACTED] Carcharhiniformes [REDACTED] Lamniformes [REDACTED] Hexanchiformes [REDACTED] Squatiniformes [REDACTED] Pristiophoriformes [REDACTED] Squaliformes [REDACTED] Sharks belong to

4876-693: The Mexico, Belize , Guatemala , and Honduras coasts. The name Caribbean derives from the Caribs , one of the region's dominant native people at the time of European contact during the late 15th century . After Christopher Columbus landed in The Bahamas in 1492 and later discovered some of the islands in The Caribbean, the Spanish term Antillas applied to the lands; stemming from this,

4968-417: The anterior and posterior nasal openings, with some species able to detect as little as one part per million of blood in seawater. The size of the olfactory bulb varies across different shark species, with size dependent on how much a given species relies on smell or vision to find their prey. In environments with low visibility, shark species generally have larger olfactory bulbs. In reefs, where visibility

5060-468: The area at a high risk of earthquakes . Underwater earthquakes pose a threat of generating tsunamis which could have a devastating effect on the Caribbean islands. Scientific data reveals that over the last 500 years, the area has seen a dozen earthquakes above 7.5 magnitude. Most recently, a 7.1 earthquake struck Haiti on January 12, 2010. The hydrology of the sea has a high level of homogeneity. Annual variations in monthly average water temperatures at

5152-468: The area is tropical , varying from tropical rainforest in some areas to tropical savanna in others. There are also some locations that are arid climates with considerable drought in some years. Rainfall varies with elevation, size, and water currents (cool upwelling keep the ABC islands arid). Warm, moist trade winds blow consistently from the east, creating both rainforest and semi-arid climates across

5244-568: The basking shark are small and non-functional. Shark skeletons are very different from those of bony fish and terrestrial vertebrates . Sharks and other cartilaginous fish ( skates and rays ) have skeletons made of cartilage and connective tissue . Cartilage is flexible and durable, yet is about half the normal density of bone. This reduces the skeleton's weight, saving energy. Because sharks do not have rib cages, they can easily be crushed under their own weight on land. The jaws of sharks, like those of rays and skates, are not attached to

5336-416: The body then flows through the posterior cardinal veins and enters the posterior cardinal sinuses . From there venous blood re-enters the heart ventricle and the cycle repeats. Most sharks are "cold-blooded" or, more precisely, poikilothermic , meaning that their internal body temperature matches that of their ambient environment. Members of the family Lamnidae (such as the shortfin mako shark and

5428-523: The coastal zone of the Caribbean Sea. Analysis of toxic metals and hydrocarbons is based on the investigation of coastal sediments that have accumulated less than 50 meters deep during the last hundred and fifty years. The project results were presented in Vienna in the forum "Water Matters", and the 2011 General Conference of said multilateral organization. After the Mediterranean, the Caribbean Sea

5520-498: The corporate sector are all eligible for financing. The project is estimated to prevent and remove at least 15 000 tonnes of marine trash, benefiting at least 20 000 individuals. The climate of the Caribbean is driven by the low latitude and tropical ocean currents that run through it. The principal ocean current is the North Equatorial Current , which enters the region from the tropical Atlantic . The climate of

5612-554: The genus Halophila , ( Halophila baillonii , Halophila engelmannii and Halophila decipiens ) are found at depths of up to 30 m (98 ft) except for Halophila engelmani which does not grow below 5 m (16 ft) and is confined to the Bahamas , Florida , the Greater Antilles and the western part of the Caribbean. Halophila baillonii has been found only in the Lesser Antilles . Marine biota in

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5704-1168: The horny keratin in hair and feathers. 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 bony fish, sharks have a complex dermal corset made of flexible collagenous fibers and arranged as a helical network surrounding their body. This works as an outer skeleton, providing attachment for their swimming muscles and thus saving energy. Their dermal teeth give them hydrodynamic advantages as they reduce turbulence when swimming. Some species of shark have pigmented denticles that form complex patterns like spots (e.g. Zebra shark ) and stripes (e.g. Tiger shark ). These markings are important for camouflage and help sharks blend in with their environment, as well as making them difficult for prey to detect. For some species, dermal patterning returns to healed denticles even after they have been removed by injury. Tails 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

5796-418: The inner ear has been lost. The ampullae of Lorenzini are the electroreceptor organs. They number in the hundreds to thousands. Sharks use the ampullae of Lorenzini to detect the electromagnetic fields that all living things produce. This helps sharks (particularly the hammerhead shark ) find prey. The shark has the greatest electrical sensitivity of any animal. Sharks find prey hidden in sand by detecting

5888-402: The intestines of many species, and as a result often linger near or in sewage outfalls. Some species, such as nurse sharks , have external barbels that greatly increase their ability to sense prey. Shark eyes are similar to the eyes of other vertebrates , including similar lenses , corneas and retinas , though their eyesight is well adapted to the marine environment with the help of

5980-451: The jaw, and are constantly replaced throughout life. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward in comparison to a conveyor belt ; some sharks lose 30,000 or more teeth in their lifetime. The rate of tooth replacement varies from once every 8 to 10 days to several months. In most species, teeth are replaced one at a time as opposed to the simultaneous replacement of an entire row, which

6072-453: The jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have two to three layers or more, depending on body size. The jaws of a large great white shark may have up to five layers. In the rostrum (snout), the cartilage can be spongy and flexible to absorb the power of impacts. Fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling

6164-415: The limits of the Caribbean Sea as follows: Although Trinidad and Tobago and Barbados are on the same continental shelf, they are considered to be in the Atlantic Ocean rather than in the Caribbean Sea. The Caribbean Sea is an oceanic sea on the Caribbean Plate . The Caribbean Sea is separated from the ocean by several island arcs of various ages. The youngest stretches from the Lesser Antilles to

6256-543: The longest lifespans at more than 100 years. Whale sharks ( Rhincodon typus ) may also live over 100 years. Earlier estimates suggested the Greenland shark ( Somniosus microcephalus ) could reach about 200 years, but a recent study found that a 5.02-metre-long (16.5 ft) specimen was 392 ± 120 years old (i.e., at least 272 years old), making it the longest-lived vertebrate known. Unlike most bony fish , sharks are K-selected reproducers, meaning that they produce

6348-722: The mainland river Orinoco and the Magdalena River . Deposits on the bottom of the Caribbean Sea and the Gulf of Mexico have a thickness of about 1 km (0.62 mi). Upper sedimentary layers relate to the period from the Mesozoic to the Cenozoic (250 million years ago) and the lower layers from the Paleozoic to the Mesozoic . The Caribbean seafloor is divided into five basins separated from each other by underwater ridges and mountain ranges. Atlantic Ocean water enters

6440-403: The most diverse marine habitats in the world, but they are fragile ecosystems. When tropical waters become unusually warm for extended periods of time, microscopic plants called zooxanthellae , which are symbiotic partners living within the coral polyp tissues, die off. These plants provide food for the corals and give them their color. The result of the death and dispersal of these tiny plants

6532-468: The north and its convergence with the Euramerica basin decreased in size. The next stage of the Caribbean Sea's formation began in the Triassic . Powerful rifting led to the formation of narrow troughs, stretching from modern Newfoundland to the Gulf of Mexico's west coast, forming siliciclastic sedimentary rocks . In the early Jurassic due to powerful marine transgression , water broke into

6624-475: The northern Atlantic as the Guiana Current and part of the North Equatorial Current enter the sea on the east. On the western side of the sea, the trade winds influence a northerly current which causes an upwelling and a rich fishery near Yucatán . The Caribbean is home to about 9% of the world's coral reefs , covering about 50,000 km (19,000 sq mi), most of which are located off

6716-510: The northern part of the sea Cuba , Hispaniola , Jamaica and Puerto Rico lie on an older island arc. The geological age of the Caribbean Sea is estimated to be between 160 and 180 million years and was formed by a horizontal fracture that split the supercontinent called Pangea in the Mesozoic Era . It is assumed the proto-caribbean basin existed in the Devonian period and in the early Carboniferous movement of Gondwana to

6808-485: The northern tip of Yucatán Tropical cyclones are a threat to the nations that rim the Caribbean Sea. While landfalls are infrequent, the resulting loss of life and property damage makes them a significant hazard to life in the Caribbean. Tropical cyclones that impact the Caribbean often develop off the West coast of Africa and make their way west across the Atlantic Ocean toward the Caribbean, while other storms develop in

6900-439: The number of green turtles has declined from 91 million to 300,000 and hawksbill turtles from 11 million to less than 30,000 by 2006. All 170 species of amphibians that live in the region are endemic. The habitats of almost all members of the toad family, poison dart frogs , tree frogs and leptodactylidae (a type of frog) are limited to only one island. The Golden coqui is in serious threat of extinction. In

6992-549: The present area of the Gulf of Mexico creating a vast shallow pool. Deep basins emerged in the Caribbean during the Middle Jurassic rifting . The emergence of these basins marked the beginning of the Atlantic Ocean and contributed to the destruction of Pangaea at the end of the late Jurassic . During the Cretaceous the Caribbean acquired a shape close to today. In the early Paleogene due to marine regression

7084-773: The reefs could severely damage the region's economy. A Protocol of the Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region came in effect in 1986 to protect the various endangered marine life of the Caribbean through forbidding human activities that would advance the continued destruction of such marine life in various areas. Currently this protocol has been ratified by 15 countries. Also, several charitable organisations have been formed to preserve

7176-612: The region have representatives of both the Indian and Pacific oceans which were caught in the Caribbean before the emergence of the Isthmus of Panama four million years ago. In the Caribbean Sea there are around 1,000 documented species of fish, including sharks ( bull shark , tiger shark , silky shark and Caribbean reef shark ), flying fish , giant oceanic manta ray , angel fish , spotfin butterflyfish , parrotfish , Atlantic Goliath grouper , tarpon and moray eels . Throughout

7268-443: The region. The tropical rainforest climates include lowland areas near the Caribbean Sea from Costa Rica north to Belize , as well as the Dominican Republic and Puerto Rico , while the more seasonal dry tropical savanna climates are found in Cuba , northern Venezuela , and southern Yucatán, Mexico . Arid climates are found along the extreme northern coast of Venezuela out to the islands including Aruba and Curaçao , as well as

7360-588: The same isthmus). The Caribbean Sea had been unknown to the populations of Eurasia until after 1492 when Christopher Columbus sailed into Caribbean waters to find a sea route to Asia. At that time, the Americas were generally unknown to most Europeans, although they had been visited in the 10th century by the Vikings . Following Columbus's discovery of the islands, the area was quickly colonized by several Western cultures (initially Spain , then later England ,

7452-451: The seawater is about 3.6%, and its density is 1,023.5–1,024.0 kg/m (63.90–63.93 lb/cu ft). The surface water color is blue-green to green . The Caribbean's depth in its wider basins and deep-water temperatures are similar to those of the Atlantic. Atlantic deep water is thought to spill into the Caribbean and contribute to the general deep water of its sea. The surface water (30 m; 100 ft) acts as an extension of

7544-540: The sewage from the Central American and Caribbean Island countries is properly treated before being released into the sea. The region has been famous for its rum production - the drink is first mentioned in records from Barbados in around 1650, although it was likely to have been produced beforehand across the other islands. The Caribbean region supports a large tourism industry. The Caribbean Tourism Organization calculates that about 12 million people

7636-403: The shark's two-chambered heart . Here, the shark pumps blood to its gills via the ventral aorta where it branches into afferent branchial arteries . Gas exchange takes place in the gills and the reoxygenated blood flows into the efferent branchial arteries, which come together to form the dorsal aorta . The blood flows from the dorsal aorta throughout the body. The deoxygenated blood from

7728-413: The spiracle) leads directly into the inner ear through a thin channel. The lateral line shows a similar arrangement, and is open to the environment via a series of openings called lateral line pores . This is a reminder of the common origin of these two vibration- and sound-detecting organs that are grouped together as the acoustico-lateralis system. In bony fish and tetrapods the external opening into

7820-414: The stomach, and instead the shark either vomits or turns its stomachs inside out and ejects unwanted items from its mouth. One of the biggest differences between the digestive systems of sharks and mammals is that sharks have much shorter intestines. This short length is achieved by the spiral valve with multiple turns within a single short section instead of a long tube-like intestine. The valve provides

7912-410: The surface do not exceed 3 °C (5.4 °F). Over the past 50 years, the Caribbean has gone through three stages: cooling until 1974, a cold phase with peaks during 1974–1976 and 1984–1986, and finally a warming phase with an increase in temperature of 0.6 °C (1.1 °F) per year. Virtually all temperature extremes were associated with the phenomena of El Niño and La Niña . The salinity of

8004-423: The surrounding water cleans their eyes. To protect their eyes some species have nictitating membranes . This membrane covers the eyes while hunting and when the shark is being attacked. However, some species, including the great white shark ( Carcharodon carcharias ), do not have this membrane, but instead roll their eyes backwards to protect them when striking prey. The importance of sight in shark hunting behavior

8096-602: The term "shark" as an informal category including extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts . Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (selachimorphs) are known from

8188-403: The thresher shark's usage of its powerful, elongated upper lobe to stun fish and squid. Unlike bony fish, sharks do not have gas-filled swim bladders for buoyancy. Instead, sharks rely on a large liver filled with oil that contains squalene , and their cartilage, which is about half the normal density of bone. Their liver constitutes up to 30% of their total body mass. The liver's effectiveness

8280-456: The top of their food chain . Select examples include the bull shark , tiger shark , great white shark , mako sharks , thresher sharks , and hammerhead sharks . Sharks are caught by humans for shark meat or shark fin soup . Many shark populations are threatened by human activities. Since 1970, shark populations have been reduced by 71%, mostly from overfishing . Until the 16th century, sharks were known to mariners as "sea dogs". This

8372-548: The word shark (referring to a sea fish) in a letter written by Thomas Beckington in 1442, which rules out a New World etymology. The oldest total-group chondrichthyans, known as acanthodians or "spiny sharks", appeared during the Early Silurian , around 439 million years ago. The oldest confirmed members of Elasmobranchii sensu lato (the group containing all cartilaginous fish more closely related to modern sharks and rays than to chimaeras ) appeared during

8464-576: Was discovered at the Mount Desert Island Biological Laboratory in Salsbury Cove, Maine that sharks have a type of salt gland located at the end of the intestine, known as the "rectal gland", whose function is the secretion of chlorides. Digestion can take a long time. The food moves from the mouth to a J-shaped stomach, where it is stored and initial digestion occurs. Unwanted items may never get past

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