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101-419: The hawksbill sea turtle ( Eretmochelys imbricata ) is a critically endangered sea turtle belonging to the family Cheloniidae . It is the only extant species in the genus Eretmochelys . The species has a global distribution that is largely limited to tropical and subtropical marine and estuary ecosystems. The appearance of the hawksbill is similar to that of other marine turtles. In general, it has

202-445: A larva swims until it finds a good site, and then becomes a polyp. This grows normally but then absorbs its tentacles and splits horizontally into a series of disks that become juvenile medusae, a process called strobilation . The juveniles swim off and slowly grow to maturity, while the polyp re-grows and may continue strobilating periodically. The adult medusae have gonads in the gastroderm , and these release ova and sperm into

303-484: A 60-year old turtle first tagged in November 1990 and again in 2011 returned to the same location. Critically endangered The IUCN Red List provides the public with information regarding the conservation status of animal, fungi, and plant species. It divides various species into seven different categories of conservation that are based on habitat range, population size, habitat, threats, etc. Each category represents

404-526: A behavioral role of these differences is speculated. Hawksbill sea turtles have a wide range , found predominantly in tropical reefs of the Indian , Pacific , and Atlantic Oceans. Of all the sea turtle species, E. imbricata is the one most associated with warm tropical waters. Two significant subpopulations are known, in the Atlantic and Indo-Pacific. In the Atlantic, hawksbill populations range as far west as

505-441: A decentralized nerve net and simple receptors . Cnidarians also have rhopalia , which are involved in gravity sensing and sometimes chemoreception. Several free-swimming species of Cubozoa and Scyphozoa possess balance-sensing statocysts , and some have simple eyes . Not all cnidarians reproduce sexually , but many species have complex life cycles of asexual polyp stages and sexual medusae stages. Some, however, omit either

606-552: A degree of fidelity after recruiting to the benthic phase however, the movement to other similar habitats is possible. Hawksbills mate biannually in secluded lagoons off their nesting beaches in remote islands throughout their range. The most significant nesting beaches are in Mexico, the Seychelles, Indonesia, Sri Lanka, and Australia. The mating season for Atlantic hawksbills usually spans April to November. Indian Ocean populations, such as

707-462: A different level of global extinction risk. Species that are considered to be Critically Endangered are placed within the "Threatened" category. As the IUCN Red List does not consider a species extinct until extensive targeted surveys have been conducted, species that are possibly extinct are still listed as Critically Endangered. IUCN maintains a list of "possibly extinct" and "possibly extinct in

808-494: A diverse group that includes all the freshwater cnidarians as well as many marine forms, and has both sessile members such as Hydra and colonial swimmers such as the Portuguese Man o' War . Staurozoa have recently been recognised as a class in their own right rather than a sub-group of Scyphozoa, and the parasitic Myxozoa and Polypodiozoa are now recognized as highly derived cnidarians rather than more closely related to

909-418: A faster rate than that of the natural extinction rate. It has largely been credited towards human impacts on climate change and the loss of biodiversity . This is along with natural forces that may create stress on the species or cause an animal population to become extinct. Currently the biggest reason for species extinction is human interaction resulting in habitat loss. Species rely on their habitat for

1010-496: A few are parasites . Many are preyed on by other animals including starfish , sea slugs , fish , turtles , and even other cnidarians. Many scleractinian corals—which form the structural foundation for coral reefs —possess polyps that are filled with symbiotic photo-synthetic zooxanthellae . While reef-forming corals are almost entirely restricted to warm and shallow marine waters, other cnidarians can be found at great depths, in polar regions , and in freshwater. Cnidarians are

1111-399: A flattened body shape, a protective carapace , and flipper -like limbs, adapted for swimming in the open ocean. E. imbricata is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium , and the saw-like appearance of its shell margins. Hawksbill shells slightly change colors, depending on water temperature. While this turtle lives part of its life in

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1212-488: A hydra's nematocysts are lost from its tentacles when capturing a brine shrimp . Used cnidocytes have to be replaced, which takes about 48 hours. To minimise wasteful firing, two types of stimulus are generally required to trigger cnidocytes: nearby sensory cells detect chemicals in the water, and their cilia respond to contact. This combination prevents them from firing at distant or non-living objects. Groups of cnidocytes are usually connected by nerves and, if one fires,

1313-452: A maximum depth of 46 m (151 ft), temperatures between 20 and 28 °C (68 and 82 °F), high salinity , and low carbon dioxide levels. Stauromedusae , although usually classified as jellyfish, are stalked, sessile animals that live in cool to Arctic waters. Cnidarians range in size from a mere handful of cells for the parasitic myxozoans through Hydra' s length of 5–20 mm ( 1 ⁄ 4 – 3 ⁄ 4  in), to

1414-407: A method to outcompete the native organisms, eventually taking over the habitat. This can lead to either the native species' extinction or causing them to become endangered, which also eventually causes extinction. Plants and animals may also go extinct due to disease. The introduction of a disease into a new habitat can cause it to spread amongst the native species. Due to their lack of familiarity with

1515-415: A minimum of 30 to 35 years. Within the sea turtles, E. imbricata has several unique anatomical and ecological traits. It is the only primarily spongivorous reptile. Because of this, its evolutionary position is somewhat unclear. Molecular analyses support Eretmochelys placement within the taxonomic tribe Carettini , including the carnivorous loggerhead and ridley sea turtles , rather than in

1616-424: A mix of calcified and uncalcified species). Cnidaria are diploblastic animals; in other words, they have two main cell layers, while more complex animals are triploblasts having three main layers. The two main cell layers of cnidarians form epithelia that are mostly one cell thick, and are attached to a fibrous basement membrane , which they secrete . They also secrete the jelly-like mesoglea that separates

1717-451: A type of muscle that, in more complex animals, arises from the middle cell layer . As a result, some recent text books classify ctenophores as triploblastic , and it has been suggested that cnidarians evolved from triploblastic ancestors. Most adult cnidarians appear as either free-swimming medusae or sessile polyps , and many hydrozoans species are known to alternate between the two forms. Both are radially symmetrical , like

1818-511: A very ancient phylum, with fossils having been found in rocks formed about 580  million years ago during the Ediacaran period , preceding the Cambrian Explosion . Other fossils show that corals may have been present shortly before 490  million years ago and diversified a few million years later. Molecular clock analysis of mitochondrial genes suggests an even older age for

1919-425: A way as to give the rear margin of its carapace a serrated look, similar to the edge of a saw or a steak knife. The turtle's carapace can reach almost 1 m (3 ft) in length. The hawksbill appears to frequently employ its sturdy shell to insert its body into tight spaces in reefs. Crawling with an alternating gait , hawksbill tracks left in the sand are asymmetrical. In contrast, the green sea turtle and

2020-469: A wheel and a tube respectively. Since these animals have no heads, their ends are described as "oral" (nearest the mouth) and "aboral" (furthest from the mouth). Most have fringes of tentacles equipped with cnidocytes around their edges, and medusae generally have an inner ring of tentacles around the mouth. Some hydroids may consist of colonies of zooids that serve different purposes, such as defense, reproduction and catching prey. The mesoglea of polyps

2121-531: A wide range of habitats, from the open ocean to lagoons and even mangrove swamps in estuaries. Little is known about the habitat preferences of early life-stage E. imbricata ; like other young sea turtles, they are assumed to be completely pelagic, remaining at sea until they mature. While they are omnivorous, sea sponges are their principal food; they constitute 70–95% of the turtles' diets. However, like many spongivores , they feed only on select species, ignoring many others. Caribbean populations feed primarily on

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2222-514: A worldwide range: some, such as Hydra , live in freshwater; Obelia appears in the coastal waters of all the oceans; and Liriope can form large shoals near the surface in mid-ocean. Among anthozoans , a few scleractinian corals , sea pens and sea fans live in deep, cold waters, and some sea anemones inhabit polar seabeds while others live near hydrothermal vents over 10 km (33,000 ft) below sea-level. Reef -building corals are limited to tropical seas between 30°N and 30°S with

2323-592: Is based, in part, on the presence in the hydra genome of genes homologous to genes in other genetically well studied species that have been demonstrated to play key roles in these DNA repair pathways. Cnidarians were for a long time grouped with Ctenophores in the phylum Coelenterata , but increasing awareness of their differences caused them to be placed in separate phyla. Modern cnidarians are generally classified into four main classes : sessile Anthozoa ( sea anemones , corals , sea pens ); swimming Scyphozoa (jellyfish) and Cubozoa (box jellies); and Hydrozoa ,

2424-531: Is both endangered and highly genetically distinct, and therefore of particular concern for conservation efforts. The World Wildlife Fund Australia (WWF-Australia) has several ongoing projects aiming at protecting the reptile. On Rosemary Island , an island in the Dampier Archipelago off the Pilbara coast of Western Australia , volunteers have been monitoring hawksbill turtles since 1986. In November 2020,

2525-465: Is known about the life history of hawksbills by comparison to several other sea turtle species. Their life history may be divided into three phases, the: (i) early life history phase from approximately 4–30 cm straight carapace length, (ii) benthic phase when the immature turtles recruit to foraging areas, and (iii) reproductive phase, when individuals reach sexual maturity and begin periodically migrating to breeding grounds. The early life history phase

2626-443: Is not as geographically resolved as other sea turtle species. This phase appears to vary across ocean regions and may occur in both pelagic and nearshore waters, possibly lasting from 0–4 years of age. One study from the central Pacific Ocean population used bomb radiocarbon (C) dating and von Bertalanffy growth models to estimate hawksbills reach sexual maturity at ~ 72 cm and 29 years of age (range 23–36 years). Hawksbills show

2727-412: Is not known how long these can survive. In some species the ova release chemicals that attract sperm of the same species. The fertilized eggs develop into larvae by dividing until there are enough cells to form a hollow sphere ( blastula ) and then a depression forms at one end ( gastrulation ) and eventually becomes the digestive cavity. However, in cnidarians the depression forms at the end further from

2828-410: Is still struggling. The mesoglea contains small numbers of amoeba -like cells, and muscle cells in some species. However, the number of middle-layer cells and types are much lower than in sponges. Polymorphism refers to the occurrence of structurally and functionally more than two different types of individuals within the same organism. It is a characteristic feature of Cnidarians, particularly

2929-509: Is threatened due to pollution and loss of nesting areas because of coastal development. Biologists estimate that the hawksbill population has declined 80 percent in the past 100–135 years. Human and animal encroachment threatens nesting sites, and small mammals dig up the eggs to eat. In the US Virgin Islands , mongooses raid hawksbill nests (along with other sea turtles, such as Dermochelys coriacea ) right after they are laid. In 1982,

3030-409: Is usually thin and often soft, but that of medusae is usually thick and springy, so that it returns to its original shape after muscles around the edge have contracted to squeeze water out, enabling medusae to swim by a sort of jet propulsion . In medusae, the only supporting structure is the mesoglea . Hydra and most sea anemones close their mouths when they are not feeding, and the water in

3131-818: The Convention on International Trade in Endangered Species . This means commercial international trade (including in parts and derivatives) is prohibited and non-commercial international trade is regulated. Hawksbill turtles are listed in Annex II of the Protocol Concerning Specially Protected Areas and Wildlife to the Convention for the Protection and Development of the Marine Environment of

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3232-560: The Eastern Pacific Hawksbill Initiative Archived 2 December 2013 at the Wayback Machine , are currently pushing efforts to research and conserve the population, which remains poorly understood. Adult hawksbill sea turtles are primarily found in tropical coral reefs . They are usually seen resting in caves and ledges in and around these reefs throughout the day. As a highly migratory species, they inhabit

3333-473: The Florida Keys and along the southeastern Atlantic coast. Several major nesting sites are found in coastal Palm Beach , Broward , and Dade County. THE FLORIDA HAWKSBILL PROJECT, is a comprehensive research and conservation Program to study and protect the region’s hawksbill sea turtles and the habitats in which they live. Within the scope of this project, numerous studies have been undertaken to characterize

3434-759: The Gulf of Mexico and as far southeast as the Cape of Good Hope in South Africa . They live off the Brazilian coast (specifically Bahia , Fernando de Noronha ). Along the East Coast of the United States , hawksbill sea turtle range from Virginia to Florida . In Florida , according to the Florida Fish and Wildlife Conservation Commission, hawksbills are found primarily on reefs in

3535-561: The IUCN Red List of Threatened Species first listed E. imbricata as endangered . This endangered status continued through several reassessments in 1986, 1988, 1990, and 1994 until it was upgraded in status to critically endangered in 1996. Two petitions challenged its status as an endangered species prior to this, claiming the turtle (along with three other species) had several significant stable populations worldwide. These petitions were rejected based on their data analysis submitted by

3636-696: The Korean Peninsula and the Japanese Archipelago south to northern New Zealand . The Philippines hosts several nesting sites, including the island of Boracay and Punta Dumalag in Davao City . Dahican Beach in Mati City , Davao Oriental , hosts one of the essential hatcheries of its kind, along with olive ridley sea turtles in the archipelagic country of the Philippines. A small group of islands in

3737-697: The Lion's mane jellyfish , which may exceed 2 m (6 ft 7 in) in diameter and 75 m (246 ft) in length. Prey of cnidarians ranges from plankton to animals several times larger than themselves. Some cnidarians are parasites , mainly on jellyfish but a few are major pests of fish. Others obtain most of their nourishment from endosymbiotic algae or dissolved nutrients. Predators of cnidarians include: sea slugs , flatworms and comb jellies , which can incorporate nematocysts into their own bodies for self-defense (nematocysts used by cnidarian predators are referred to as kleptocnidae); starfish , notably

3838-455: The Seychelles hawksbill population, mate from September to February. After mating, females drag their heavy bodies high onto the beach during the night. They clear an area of debris and dig a nesting hole using their rear flippers, then lay clutches of eggs and cover them with sand. Caribbean and Florida nests of E. imbricata typically contain around 140 eggs. After the hours-long process,

3939-465: The bilaterians . Stauromedusae, small sessile cnidarians with stalks and no medusa stage, have traditionally been classified as members of the Scyphozoa, but recent research suggests they should be regarded as a separate class, Staurozoa. The Myxozoa , microscopic parasites , were first classified as protozoans . Research then found that Polypodium hydriforme , a non-Myxozoan parasite within

4040-451: The corals Hetroxenia and Leptogorgia , depend almost completely on their endosymbionts and on absorbing dissolved nutrients. Cnidaria give their symbiotic algae carbon dioxide , some nutrients, and protection against predators. Predatory species use their cnidocytes to poison or entangle prey, and those with venomous nematocysts may start digestion by injecting digestive enzymes . The "smell" of fluids from wounded prey makes

4141-517: The crown group of cnidarians, estimated around 741  million years ago , almost 200 million years before the Cambrian period, as well as before any fossils. Recent phylogenetic analyses support monophyly of cnidarians, as well as the position of cnidarians as the sister group of bilaterians . The term cnidaria derives from the Ancient Greek word knídē ( κνίδη “nettle”), signifying

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4242-449: The leatherback turtle have a more symmetrical gait. Due to its consumption of venomous cnidarians , hawksbill sea turtle flesh can become toxic . The hawksbill is biofluorescent and is the first reptile recorded with this characteristic. It is unknown if the effect is due to the turtle's diet, which includes biofluorescent organisms like the hard coral Physogyra lichtensteini . Males have more intense pigmentation than females, and

4343-432: The medusae . These "nettle cells" function as harpoons , since their payloads remain connected to the bodies of the cells by threads. Three types of cnidocytes are known: The main components of a cnidocyte are: It is difficult to study the firing mechanisms of cnidocytes as these structures are small but very complex. At least four hypotheses have been proposed: Cnidocytes can only fire once, and about 25% of

4444-511: The phase of the moon . Many species of Cnidaria may spawn simultaneously in the same location, so that there are too many ova and sperm for predators to eat more than a tiny percentage — one famous example is the Great Barrier Reef , where at least 110 corals and a few non-cnidarian invertebrates produce enough gametes to turn the water cloudy. These mass spawnings may produce hybrids , some of which can settle and form polyps, but it

4545-509: The polyp and medusa forms, or of zooids within colonial organisms like those in Hydrozoa . In Hydrozoans , colonial individuals arising from individual zooids will take on separate tasks. For example, in Obelia there are feeding individuals, the gastrozooids ; the individuals capable of asexual reproduction only, the gonozooids, blastostyles and free-living or sexually reproducing individuals,

4646-450: The "main" islands of Oahu , Maui , Molokai , and Hawaii . In Australia , hawksbills are known to nest on Milman Island in the Great Barrier Reef . Hawksbill sea turtles nest as far west as Cousine Island in the Seychelles , where the species since 1994 is legally protected, and the population is showing some recovery. The Seychelles' inner islands and islets, such as Aldabra , are popular feeding grounds for immature hawksbills. In

4747-516: The Japanese hawksbill shell trade was around 30,000 kg (66,000 lb) of raw shells per year. In Europe, hawksbill sea turtle shells were harvested by the ancient Greeks and ancient Romans for jewellery, such as combs, brushes, and rings. Recently, processed shells were regularly available in large amounts in countries including the Dominican Republic and Colombia . Global estimates of

4848-632: The Marine Turtle Specialist Group (MTSG). The MTSG data showed the worldwide hawksbill sea turtle population had declined by 80% in the three most recent generations, and no significant population increase had occurred as of 1996. CR A2 status was denied, however, because the IUCN did not find sufficient data to show the population likely to decrease by a further 80%. The species (along with the entire Cheloniidae family) has been listed in Appendix I of

4949-575: The West. Along the south coast of Java, stuffed hawksbill turtles are sold in souvenir shops, though numbers have decreased in the last two decades. In Japan , the turtles are harvested for their shell scutes , called bekko in Japanese . Bekko is used in various personal implements, such as eyeglass frames and the shamisen (Japanese traditional three-stringed instrument) picks. In 1994, Japan stopped importing hawksbill shells from other nations. Prior to this,

5050-623: The Wider Caribbean Region (SPAW), part of the Cartagena Convention . The United States Fish and Wildlife Service and National Marine Fisheries Service have classified hawksbills as endangered under the Endangered Species Act since 1970. The US government established several recovery plans for protecting E. imbricata . The Zoological Society of London has inscribed the reptile as an EDGE species , meaning that it

5151-844: The coiled thread reminiscent of cnidocytes. The word was first coined in 1766 by the Swedish naturalist Peter Simon Pallas . Cnidarians form a phylum of animals that are more complex than sponges , about as complex as ctenophores (comb jellies), and less complex than bilaterians , which include almost all other animals. Both cnidarians and ctenophores are more complex than sponges as they have: cells bound by inter-cell connections and carpet-like basement membranes ; muscles ; nervous systems ; and some have sensory organs. Cnidarians are distinguished from all other animals by having cnidocytes that fire harpoon -like structures that are mainly used to capture prey. In some species, cnidocytes can also be used as anchors. Cnidarians are also distinguished by

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5252-505: The connecting tunnels, so that gastroderm cells can absorb the nutrients. Absorption may take a few hours, and digestion within the cells may take a few days. The circulation of nutrients is driven by water currents produced by cilia in the gastroderm or by muscular movements or both, so that nutrients reach all parts of the digestive cavity. Nutrients reach the outer cell layer by diffusion or, for animals or zooids such as medusae which have thick mesogleas , are transported by mobile cells in

5353-770: The dangerous jellyfish-like hydrozoan, the Portuguese man o' war ( Physalia physalis ). Hawksbills close their unprotected eyes when they feed on these cnidarians. The man o' war's stinging cells cannot penetrate the turtles' armored heads. Hawksbills are highly resilient and resistant to their prey. Some of the sponges they eat, such as Aaptos aaptos , Chondrilla nucula , Tethya actinia , Spheciospongia vesparium , and Suberites domuncula , are highly (often lethally) toxic to other organisms. In addition, hawksbills choose sponge species with significant numbers of siliceous spicules , such as Ancorina , Geodia ( G. gibberosa ), Ecionemia , and Placospongia . Less

5454-420: The digestive cavity then acts as a hydrostatic skeleton , rather like a water-filled balloon. Other polyps such as Tubularia use columns of water-filled cells for support. Sea pens stiffen the mesoglea with calcium carbonate spicules and tough fibrous proteins , rather like sponges . In some colonial polyps, a chitinous epidermis gives support and some protection to the connecting sections and to

5555-440: The digestive cavity without opening the mouth. This improves respiration after feeding and allows these animals, which use the cavity as a hydrostatic skeleton , to control the water pressure in the cavity without expelling undigested food. Cnidaria that carry photosynthetic symbionts may have the opposite problem, an excess of oxygen, which may prove toxic . The animals produce large quantities of antioxidants to neutralize

5656-421: The disease or little resistance, the native species can die off. Cnidaria Cnidaria ( / n ɪ ˈ d ɛər i ə , n aɪ -/ nih- DAIR -ee-ə, NY - ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in fresh water and marine environments (predominantly the latter), including jellyfish , hydroids , sea anemones , corals and some of

5757-571: The eastern Pacific, hawksbills are known to occur from the Baja Peninsula in Mexico south along the coast to southern Peru . Nonetheless, as recently as 2007, the species had been considered extirpated mainly in the region. Important remnant nesting and foraging sites have since been discovered in Mexico, El Salvador , Nicaragua , and Ecuador , providing new research and conservation opportunities. In contrast to their traditional roles in other parts of

5858-620: The egg cells of sturgeon , is closely related to the Myxozoa and suggested that both Polypodium and the Myxozoa were intermediate between cnidarians and bilaterian animals. More recent research demonstrates that the previous identification of bilaterian genes reflected contamination of the Myxozoan samples by material from their host organism, and they are now firmly identified as heavily derived cnidarians, and more closely related to Hydrozoa and Scyphozoa than to Anthozoa. Some researchers classify

5959-556: The excess oxygen. All cnidarians can regenerate , allowing them to recover from injury and to reproduce asexually . Medusae have limited ability to regenerate, but polyps can do so from small pieces or even collections of separated cells. This enables corals to recover even after apparently being destroyed by predators. Cnidarian sexual reproduction often involves a complex life cycle with both polyp and medusa stages. For example, in Scyphozoa (jellyfish) and Cubozoa (box jellies)

6060-580: The extinct conulariids as cnidarians, while others propose that they form a completely separate phylum . Current classification according to the World Register of Marine Species : Many cnidarians are limited to shallow waters because they depend on endosymbiotic algae for much of their nutrients. The life cycles of most have polyp stages, which are limited to locations that offer stable substrates. Nevertheless, major cnidarian groups contain species that have escaped these limitations. Hydrozoans have

6161-454: The eyes probably do not form images, Cubozoa can clearly distinguish the direction from which light is coming as well as negotiate around solid-colored objects. Cnidarians feed in several ways: predation , absorbing dissolved organic chemicals, filtering food particles out of the water, obtaining nutrients from symbiotic algae within their cells, and parasitism. Most obtain the majority of their food from predation but some, including

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6262-543: The fact that they have only one opening in their body for ingestion and excretion i.e. they do not have a separate mouth and anus. Like sponges and ctenophores, cnidarians have two main layers of cells that sandwich a middle layer of jelly-like material, which is called the mesoglea in cnidarians; more complex animals have three main cell layers and no intermediate jelly-like layer. Hence, cnidarians and ctenophores have traditionally been labelled diploblastic , along with sponges. However, both cnidarians and ctenophores have

6363-418: The female returns to the sea. Their nests can be found throughout beaches in about 60 countries. Hatchlings, usually weighing less than 24 g (0.85 oz), hatch at night after around two months. These newly emergent hatchlings are dark-colored, with heart-shaped carapaces measuring approximately 2.5 cm (0.98 in) long. They instinctively crawl into the sea, attracted by the moon's reflection on

6464-595: The freshwater cnidarians as well as many marine forms, and which has both sessile members, such as Hydra , and colonial swimmers (such as the Portuguese man o' war )). Staurozoa have recently been recognised as a class in their own right rather than a sub-group of Scyphozoa, and the highly derived parasitic Myxozoa and Polypodiozoa were firmly recognized as cnidarians only in 2007. Most cnidarians prey on organisms ranging in size from plankton to animals several times larger than themselves, but many obtain much of their nutrition from symbiotic dinoflagellates , and

6565-792: The genus name Eretmochelys from the Ancient Greek roots eretmo and chelys , corresponding to " oar " and "turtle", respectively, in reference to the turtles' oar-like front flippers. The species name imbricate is Latin , corresponding to the English term imbricate , in reference to the turtles' shingle-like, overlapping carapace scutes. Adult hawksbill sea turtles typically grow to 1 m (3 ft) in length, weighing around 80 kg (180 lb) on average. The heaviest hawksbill ever captured weighed 127 kg (280 lb). The turtle's shell, or carapace, has an amber background patterned with an irregular combination of light and dark streaks, with predominantly black and mottled-brown colors radiating to

6666-672: The hawksbill aggregations found in southeast Florida waters, and educational programs have been developed to engage the local dive community in the protection of hawksbill sea turtles and coral reef habitats. This program is hosted by the National Save the Sea Turtle Foundation, located in Fort Lauderdale, Florida .Throughout their global range, hawksbill turtles are known to closely associate with coral reef habitats, mostly due to their preference for eating sponges and corals. Due to

6767-618: The hawksbill sea turtle as Testudo imbricata in 1766, in the 12th edition of his Systema Naturae . In 1843, Austrian zoologist Leopold Fitzinger moved it into the genus Eretmochelys . In 1857, the species was temporarily misdescribed as Eretmochelys imbricata squamata . Neither the IUCN nor the United States Endangered Species Act assessment processes recognize any formal subspecies, but instead recognize one globally distributed species with populations, subpopulations, or regional management units. Fitzinger derived

6868-448: The hawksbill, were eaten as delicacies in China . Beyond direct consumption for food, many cultures have also exploited hawksbill populations for their ornate carapace shells, known variously as tortoiseshell , turtle shell, and bekko . In China, the hawksbill is called dai mei or dai mao ("tortoise-shell turtle"), and was used to make and decorate a variety of small items, as it was in

6969-515: The historical exploitation of hawksbills have received recent attention. From 1950-1992, one pioneering study estimated that as many as 1.37 million adult hawksbills were killed in the international tortoiseshell trade alone. With the aid of substantial additional trade data, including official trade records from the imperial Japanese archives, the international trade of tortoiseshell was recently updated to have killed approximately 8.98 million hawksbills (range 4.64 to 9.83 million) from 1844-1992. Most of

7070-435: The involvement of sexual reproduction process, was observed in both Hydrozoa ( Turritopsis dohrnii and Laodicea undulata ) and Scyphozoa ( Aurelia sp.1 ). Anthozoa have no medusa stage at all and the polyps are responsible for sexual reproduction. Spawning is generally driven by environmental factors such as changes in the water temperature, and their release is triggered by lighting conditions such as sunrise, sunset or

7171-589: The large extent of Florida’s barrier reefs (approx. 350 linear miles), the Hawksbill Project focuses on representative sites in the northern, central, and southern sections of the Southeast Florida Reef Tract. The barrier reefs of northern Palm Beach County, the patch reefs of the northern Keys, and the finger reefs of Key West are the primary locations for their sampling efforts In the Caribbean ,

7272-407: The layers. The layer that faces outwards, known as the ectoderm ("outside skin"), generally contains the following types of cells: In addition to epitheliomuscular, nerve and interstitial cells, the inward-facing gastroderm ("stomach skin") contains gland cells that secrete digestive enzymes . In some species it also contains low concentrations of cnidocytes, which are used to subdue prey that

7373-556: The lower parts of individual polyps. A few polyps collect materials such as sand grains and shell fragments, which they attach to their outsides. Some colonial sea anemones stiffen the mesoglea with sediment particles. A mineralized exoskeleton made of calcium carbonate is found in subphylum Anthozoa in the order Scleractinia (stony corals; class Hexacorallia) and the class Octocorallia , and in subphylum Medusozoa in three hydrozoan families in order Anthoathecata ; Milleporidae , Stylasteridae and Hydractiniidae (the latter with

7474-661: The main nesting beaches are in the Lesser Antilles , Barbados , Guadeloupe, Tortuguero in Costa Rica , and the Yucatan . They feed in the waters off Cuba and around Mona Island near Puerto Rico , among other places. In the Indian Ocean , hawksbills are a common sight along the east coast of Africa. You can find them in the seas surrounding Madagascar and Mozambique , and island groups like Primeiras e Segundas , which include

7575-631: The margin of the bell that work together to control the motor nerve net, that directly innervates the swimming muscles. Most cnidarians also have a parallel system. In scyphozoans, this takes the form of a diffuse nerve net, which has modulatory effects on the nervous system. As well as forming the "signal cables" between sensory neurons and motoneurons, intermediate neurons in the nerve net can also form ganglia that act as local coordination centers. Communication between nerve cells can occur by chemical synapses or gap junctions in hydrozoans, though gap junctions are not present in all groups. Cnidarians have many of

7676-469: The maturation of the reproductive organs and the production of gametes and thus determine sexual maturity. Like many reptiles, all marine turtles of the same aggregation are highly unlikely to reach sexual maturity at the same size and thus age. Age at maturity has been estimated to occur between 10 and 25 years of age for Caribbean hawksbills. Turtles nesting in the Indo-Pacific region may reach maturity at

7777-645: The medusae of some hydrozoans can divide down the middle. Scyphozoan polyps can both bud and split down the middle. In addition to both of these methods, Anthozoa can split horizontally just above the base. Asexual reproduction makes the daughter cnidarian a clone of the adult. The ability of Cnidarians to asexually reproduce ensures a greater number of mature medusa that can mature to reproduce sexually. Two classical DNA repair pathways, nucleotide excision repair and base excision repair , are present in hydra , and these repair pathways facilitate unhindered reproduction. The identification of these pathways in hydra

7878-580: The mesoglea. Indigestible remains of prey are expelled through the mouth. The main waste product of cells' internal processes is ammonia , which is removed by the external and internal water currents. There are no respiratory organs, and both cell layers absorb oxygen from and expel carbon dioxide into the surrounding water. When the water in the digestive cavity becomes stale it must be replaced, and nutrients that have not been absorbed will be expelled with it. Some Anthozoa have ciliated grooves on their tentacles, allowing them to pump water out of and into

7979-447: The movements of internal mineral grains called statoliths. If the body tilts in the wrong direction, the animal rights itself by increasing the strength of the swimming movements on the side that is too low. Most species have ocelli ("simple eyes"), which can detect sources of light. However, the agile box jellyfish are unique among Medusae because they possess four kinds of true eyes that have retinas , corneas and lenses . Although

8080-611: The only animals that can reproduce both sexually and asexually. Cnidarians mostly have two basic body forms: swimming medusae and sessile polyps , both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes, which are specialized stinging cells used to capture prey. Both forms have a single orifice and body cavity that are used for digestion and respiration . Many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids , or both (hence they are trimorphic ). Cnidarians' activities are coordinated by

8181-493: The open ocean, it spends more time in shallow lagoons and coral reefs . The World Conservation Union , primarily as a result of human fishing practices, classifies E. imbricata as critically endangered . Hawksbill shells were the primary source of tortoiseshell material used for decorative purposes. The Convention on International Trade in Endangered Species (CITES) regulates the international trade of hawksbill sea turtles and products derived from them. Linnaeus described

8282-649: The orders Astrophorida , Spirophorida , and Hadromerida in the class Demospongiae . Aside from sponges, hawksbills feed on algae , marine plants ( seagrasses ), woody plant remains, mangrove fruits and seeds , cnidarians ( comb jellies and other jellyfish , hydrozoans , hard corals , corallimorphs , zoanthids , and sea anemones ), bryozoans , mollusks ( squid , snails , nudibranchs , bivalves , and tusk shells ), echinoderms ( sea cucumbers and sea urchins ), tunicates , fish and their eggs , crustaceans , and arthropods ( crabs , lobsters , barnacles , copepods , and beetles ). They also feed on

8383-486: The parents are immobile, these feeding capabilities extend the larvae's range and avoid overcrowding of sites. Scyphozoan and hydrozoan larvae have little yolk and most lack endosymbiotic algae, and therefore have to settle quickly and metamorphose into polyps. Instead, these species rely on their medusae to extend their ranges. All known cnidaria can reproduce asexually by various means, in addition to regenerating after being fragmented. Hydrozoan polyps only bud, while

8484-529: The polyp or the medusa stage, and the parasitic classes evolved to have neither form. Cnidarians were formerly grouped with ctenophores , also known as comb jellies, in the phylum Coelenterata , but increasing awareness of their differences caused them to be placed in separate phyla. Cnidarians are classified into four main groups: the almost wholly sessile Anthozoa ( sea anemones , corals , sea pens ); swimming Scyphozoa ( jellyfish ); Cubozoa (box jellies); and Hydrozoa (a diverse group that includes all

8585-450: The polyp stage completely, and cubozoan polyps produce only one medusa. Hydrozoa have a variety of life cycles. Some have no polyp stages and some (e.g. hydra ) have no medusae. In some species, the medusae remain attached to the polyp and are responsible for sexual reproduction; in extreme cases these reproductive zooids may not look much like medusae. Meanwhile, life cycle reversal, in which polyps are formed directly from medusae without

8686-408: The resources needed for their survival. If the habitat becomes destroyed, the population will see a decline in their numbers. Activities that cause loss of habitat include pollution , urbanization , and agriculture . Another reason for plants and animals to become endangered is due to the introduction of invasive species . Invasive species invade and exploit a new habitat for its natural resources as

8787-1273: The rest of the group requires a weaker minimum stimulus than the cells that fire first. Medusae swim by a form of jet propulsion: muscles, especially inside the rim of the bell, squeeze water out of the cavity inside the bell, and the springiness of the mesoglea powers the recovery stroke. Since the tissue layers are very thin, they provide too little power to swim against currents and just enough to control movement within currents. Hydras and some sea anemones can move slowly over rocks and sea or stream beds by various means: creeping like snails, crawling like inchworms , or by somersaulting . A few can swim clumsily by waggling their bases. Cnidarians are generally thought to have no brains or even central nervous systems. However, they do have integrative areas of neural tissue that could be considered some form of centralization. Most of their bodies are innervated by decentralized nerve nets that control their swimming musculature and connect with sensory structures, though each clade has slightly different structures. These sensory structures, usually called rhopalia, can generate signals in response to various types of stimuli such as light, pressure, chemical changes, and much more. Medusa usually have several of them around

8888-586: The same neurotransmitters as bilaterians, including chemicals such as glutamate, GABA, and glycine. Serotonin, dopamine, noradrenaline, octopamine, histamine, and acetylcholine, on the other hand, are absent. This structure ensures that the musculature is excited rapidly and simultaneously, and can be directly stimulated from any point on the body, and it also is better able to recover after injury. Medusae and complex swimming colonies such as siphonophores and chondrophores sense tilt and acceleration by means of statocysts , chambers lined with hairs which detect

8989-625: The sides. Several characteristics of the hawksbill sea turtle distinguish it from other sea turtle species. Its elongated, tapered head ends in a beak-like mouth (from which its common name is derived), and its beak is more sharply pronounced and hooked than others. The hawksbill's forelimbs have two visible claws on each flipper. A readily distinguished characteristic of the hawksbill is the pattern of thick scutes that make up its carapace. While its carapace has five central scutes and four pairs of lateral scutes like several members of its family, E. imbricata 's posterior scutes overlap in such

9090-464: The smallest marine parasites . Their distinguishing features are a decentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey . Their bodies consist of mesoglea , a non-living, jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Cnidarians are also some of

9191-567: The southwest of the archipelago is named the " Turtle Islands " because two species of sea turtles nest there: the hawksbill and the green sea turtle. In January 2016, a juvenile was seen in Gulf of Thailand . A 2018 article by The Straits Times reported that around 120 hawksbill juvenile turtles recently hatched at Pulau Satumu , Singapore . Commonly found in Singapore waters, hawksbill turtles have returned to areas such East Coast Park and Palau Satumu to nest. In Hawaii, hawksbills mostly nest on

9292-452: The tentacles and oral arms often have rows of cilia whose beating creates currents that flow towards the mouth, and some produce nets of mucus to trap particles. Their digestion is both intra and extracellular. Once the food is in the digestive cavity, gland cells in the gastroderm release enzymes that reduce the prey to slurry, usually within a few hours. This circulates through the digestive cavity and, in colonial cnidarians, through

9393-673: The tentacles fold inwards and wipe the prey off into the mouth. In medusae, the tentacles around the edge of the bell are often short and most of the prey capture is done by "oral arms", which are extensions of the edge of the mouth and are often frilled and sometimes branched to increase their surface area. These "oral arms" aid in Cnidarians ability to move prey towards their mouth once it has been poisoned and entangled. Medusae often trap prey or suspended food particles by swimming upwards, spreading their tentacles and oral arms and then sinking. In species for which suspended food particles are important,

9494-497: The trade occurred in the Pacific Ocean basin, and the countries of origin and trade routes bore similarity to what is known of illegal, unreported and unregulated fishing (IUU fishing). Consensus has determined sea turtles, including E. imbricata to be at least threatened, because of their slow growth and maturity and low reproductive rates. Humans have killed many adult turtles, both accidentally and deliberately. Their existence

9595-442: The tribe Chelonini , which includes the herbivorous green turtle . The hawksbill probably evolved from carnivorous ancestors. Throughout the world, hawksbill turtles have been hunted by humans, though it is illegal to capture, kill, and trade hawksbills in many countries today. In some parts of the world, hawksbill turtles and their eggs continue to be exploited as food. As far back as the fifth century BCE, sea turtles, including

9696-582: The turtle protection island of Ilha do Fogo . Hawksbills are also common along the southern Asian coast, including the Persian Gulf , the Red Sea , and the Indian subcontinent and Southeast Asia coasts. They are present across the Malay Archipelago and northern Australia . Their Pacific range is limited to the ocean's tropical and subtropical regions. In the west, it extends from the southwestern tips of

9797-730: The water (disrupted by light sources such as street lamps and lights). While they emerge under the cover of darkness, hatchlings that do not reach the water by daybreak are preyed upon by shorebirds , shore crabs , and other predators. Hawksbills evidently reach maturity after 20 years. Their lifespan is unknown. Like other sea turtles, hawksbills are solitary for most of their lives; they meet only to mate. They are highly migratory . Because of their tough carapaces , adults' only predators are humans, sharks , estuarine crocodiles , octopuses , and some pelagic fish species. A series of biotic and abiotic cues, such as individual genetics, foraging quantity and quality, or population density, may trigger

9898-487: The water in the breeding season. This phenomenon of succession of differently organized generations (one asexually reproducing, sessile polyp, followed by a free-swimming medusa or a sessile polyp that reproduces sexually) is sometimes called "alternation of asexual and sexual phases" or "metagenesis", but should not be confused with the alternation of generations as found in plants. Shortened forms of this life cycle are common, for example some oceanic scyphozoans omit

9999-491: The wild" species, modelled on categories used by BirdLife International to categorize these taxa . To be defined as Critically Endangered in the Red List, a species must meet any of the following criteria (A–E) ("3G/10Y" signifies three generations or ten years—whichever is longer—over a maximum of 100 years; "MI" signifies Mature Individuals): The current extinction crisis is witnessing extinction rates that are occurring at

10100-458: The world, where hawksbills primarily inhabit coral reefs and rocky substrate areas, in the eastern Pacific, hawksbills tend to forage and nest principally in mangrove estuaries, such as those present in the Bahia de Jiquilisco (El Salvador), Gulf of Fonseca (Nicaragua, El Salvador, and Honduras), Estero Padre Ramos (Nicaragua), and the Gulf of Guayaquil (Ecuador). Multi-national initiatives, such as

10201-504: The yolk (at the animal pole ), while in bilaterians it forms at the other end ( vegetal pole ). The larvae, called planulae , swim or crawl by means of cilia . They are cigar-shaped but slightly broader at the "front" end, which is the aboral, vegetal-pole end and eventually attaches to a substrate if the species has a polyp stage. Anthozoan larvae either have large yolks or are capable of feeding on plankton , and some already have endosymbiotic algae that help to feed them. Since

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