Marine Turtle

(Jrt)

Marine Turtle
The sea turtles (Chelonioidea) turtles are present in all the oceans of the world except the Arctic Ocean.
The leatherback turtle is the biggest, measuring 2 meters long, 1m to 1.50m wide and weighing 600 kg. The average size of other species ranging from 50cm to 1m and is proportionately less wide.

Description
The sea turtles, like other turtles (Testudines) are reptiles ectothermes with a pulmonary respiratory system, which corresponded to a complete adaptation to life on earth. In addition to kidneys, glands near their eyes are able to expel the excess salt from their bloodstream. Their metabolism is capable of withstanding high concentration of CO2 in the deep dives. They can remove 35 to 52% of the oxygen in their breathing. Their vision is very developed. The eyes are protected by three eyelids, their hearing is particularly fine even if they have no external ears, but an inner ear, in a hearing plate. Their smell is however not very efficient. The sea turtles have only one excretory outlet, which is also used for reproduction.

The sex of turtles is not apparent that also are reflected in their secondary sexual characteristics that man can determine the sex of a turtle. It is defined by puberty period where they appear. The most obvious is the size of the tail, much larger in males. The size of teeth among cheloniidés is another. However, these sexual characteristics are not very marked and some females can fly. Only a genetic examination can be sure of the sex of the animal.

The shell
Their shells flattened them better hydrodynamic characteristics and play an obvious role of protection, but some scientists believe that they can store heat. This adaptation, gained after their return to the marine environment, allows them to descend deep, where water temperatures are low. In return, they have lost their ability to withdraw their members. As for other aquatic turtles, their shells are lighter car fitted with fontanelles. The Dermochelyidae, the largest sea turtles, have lost their scales and their shells are covered with a thick leather. Like other turtles, they do not mutate and have a superficial exfoliation partial plates corneas of the skeleton.

According to some theories, their shell, at least for the leatherback turtle, helps to maintain a sufficient body temperature when venturing into colder waters or dive. But this assumption is discussed, because the reptiles, cold-blooded animals, are expected to be poïkilothermes.

Features
They can swim quickly and several species are capable of speeds up to 35 km / h; unlike the freshwater turtles, they argue a simultaneous action by members earlier.

At birth, there is at sea turtles no external anatomical feature that would distinguish one from the other sex.

It is believed that some sea turtles can exceed 150 years. It was measured a record 6 hours diving for a green turtle.

Reproduction
The collective clutches of sea turtles are called arribadas. They take place on the beaches at the beginning and the end of the lunar cycles when the tide is at its lowest and the lowest undertow.

After several years of maturation, turtles can reproduce. The couplings take place at sea near the nesting sites or during migration (between feeding sites and sites lay) a month or two before laying.

During mating, the male clings by its two previous claws (which are secondary sexual characteristics) to the shell of the female. Females may store the sperm of males for several months or years in a decline in their oviduct. Females lay not only on their birthplace, a few meters or hundreds of metres depending on the species. It is usually through the night (too long exposure to the sun would be fatal), at dusk, often at the rising tide that females go out to lay on their beach sand origin. The female can store sperm to fertilize eggs of successive. The sex of young depends on the temperature during the incubation of eggs.

They dig a hole in the sand with their feet or trains mostly back and lay 70 to 200 eggs (depending on species) before they recover and return to the sea Some eggs are not fertilized, other incubate for about two months. As with other turtles, the sex of the embryo depends on the temperature of the nest in a certain period of incubation. All the young turtles hatch at the same time and head to sea
Only a very small portion (about 1%) return on the beach who was born because they are prey to many predators.

Stages of Life
Depending on their age, the turtle is not nourished in the same way and does not live in similar environments. There are:

* The egg stage
* The stadium newborn: newborn leaves the egg, emerges from the nest usually in a group takes refuge in the sea where he swims actively to sea for several days (three to six depending on the species).
* The juvenile pelagic stage: this stage begins when the young turtles abandon their active swimming behavior and focus more on food in bear leaving by sea currents. The comments at this stage are extremely rare. The behavior may also be different depending on the species. The various delivered suggest that all species do not live in the same habitat.
* The juvenile benthic: juveniles are sédentarisent on benthic areas (except for the leatherback turtle). Their eating habits seem to change, their predators, too.
* The sub-adult stage: it begins at puberty, when secondary sexual characteristics appear. Marine turtles of the same species do not become sexually mature at the same size.
* The adult: adults migrate from their area of life to their spawning area. All species of marine turtles are faithful to their nesting place, with some variations depending on the species.

Food
The sea turtles are omnivores with trends towards higher plants or food meat. Thus, the green turtle and tortoise frank Pacific are primarily herbivores. The caouanne, the olive ridley turtle and a flat back especially carnivorous and consume shellfish, crustaceans, small fish and other marine invertebrates. The leatherback turtle is omnivorous and consumes more cnidarians. The hawksbill also omnivorous, consuming, as the leatherback turtle, cnidarians but is also rare for a vertebrate, spongivore.

The turtles must store a lot of energy for their migrations and their eggs. For this reason, their diet plays a direct role in their fertility. This was demonstrated in corroborating the numbers of eggs and El Niño, a warming water and providing more vegetation, increases the number of migrations two years later, while a cooling lowers the number of migrations two years later.

Identification of adults
The easiest to identify is, of course, the leatherback turtle because of its lack of scales. It is also the largest sea turtles. The Cheloniidea, they have a shell without hull and scales. When it has more than six pairs of side plates on the carapace, it may be a olive ridley, with five or six pairs, this may be one or caouanne turtle Kemp. With four pairs, it is a green turtle or hawksbill turtle. There are easily caouanne and Kemp's ridley by their color, the first is red and orange second gray-green. There are also green turtle hawksbill turtle by the shape of the tooth and the number of scales préfrontales. The turtle-backed flat has one claw a flipper, sometimes marginal scutes recourbées up, with one pair of scales préfrontales. It may be noted that the olive ridley and Kemp's ridley have four pairs of plates inframarginales, each pierced with a pore near its edge.

Identification of newborns

* The new-born caouanne is dark brown with clear edge, fins lined with pale yellow.
* The new-born lute has much larger fins and skin rough, with a provision netted small scales. Its carapace is black, with white crests side while its plastron white, light brown marbled.
* The new-born of a green turtle carapace brownish black, its posterior and feet-fins with a white board, below the neck, body and legs-fins are yellowish white.
* The new-born hawksbill turtle is reddish brown.
* The carapace dark gray newborn of Kemp's ridley has three longitudinal ridges. There are two peaks on the plastron more pale. In some individuals, fins are lined with white, axilla tinged with green.
* The scales of newborns of the turtle-backed flat are dark brown but bordurées so they are easily distinguished.

Ecology
The turtles are often seen accompanied by rémoras removed that feed its parasites. This feature is used by some hunters turtles Indian Ocean fishing for green turtle or hawksbill. The rémora committed grasps the tortoise which can then be péchée. As with other turtles, one can also observe barnacles and filamentous algae on their shells.

Distribution
They are found in all the world's seas with a clear preference for the equatorial areas where they must lay ahead, except that the Caouanne pond in the Mediterranean areas. The leatherback turtle is the tortoise can live up to Scandinavia. The Chelonnidae remain in warmer waters but was able to make a few observations until Channel. They prefer a water temperature between 25 and 30 ° C. They therefore not n'hibernent but their activity decreased during the cold season.

Migration
All marine turtles appear to migrate, except males olive. They appear regularly use some biological corridors submarines, in order to regain their spawning, thanks to an extraordinary sense of time and direction. We think they are particularly sensitive to the Earth's magnetic field and it certainly use it for their migration. We know also that they follow in their migration ocean currents. Numerous studies seeking to understand their migration to better protect them.

The fact that most species lay back to where they hatched, seems to indicate that they have memorized the characteristics including magnetic.

Predators
The sea turtles have natural enemies such as the great white shark, the shark and the shark tigre bulldog as evidenced by the scars on their shells found, but above all humans. However, they are especially vulnerable because of their reproductive system. They must approach the coast to lay, man is there, its main predator. The eggs are left unattended. The man is not the only one to collect eggs. It has shown that small mammals, dogs and even mongooses (on the beaches VA) plunder nests. More surprising still, eggs are also directly threatened by insects and, in French Guiana including the leatherback turtle, by courtiliere. Then newborns, very vulnerable, usually leaving at night, when the temperature drops. At the slightest increase in temperature, they stop any activity.

When they emerge from the sand, they are going to light signals, usually waves flashing in the light of the moon or stars. Their survival is strongly hampered by urbanization and lights that result. These lights change the trajectories of baby turtles that do necessarily lead to the sea

They must earn the sea as soon as possible, why, we must escape to mammals like dogs or, for example, leatherback turtles from French Guiana, Coatis, birds, lizards, and crabs which are omnivorous very voracious. Finally they reach the most isolated areas or marine protected beyond a big predation arrival of big fish, cephalopods (octopus, squid) or seabirds from the wait. It is thought that newborns also moving to Wednesday (night) through the Earth's magnetic field. Once off and currents, they shelter in the surrounding masses floating.

In addition to predators, landslides and settling sand can damage or destroy the nest.

The people
For most species, it is very difficult to know precisely the number of sea turtles because of two behaviors. On the one hand their migratory behaviour does not allow us to deduct the number of turtles localized observations, their density can vary depending on locations, times, etc. ... On the other hand, one can not deduce the number of females watching the pundits, because their spawning frequency varies widely depending on the locations and ages of turtles. The large number of beaches where they will lay their great longevity, as well as the important time before reaching sexual maturity, have enabled the species to resist the bulk made by humans, however, when these levies reach a size criticism, the turtle population decline and may take many decades before they grow again.

It has been observed, however, increases at the local level. According to a study published in Kélonia August 9, 2007, the population of sea turtles found on the island Europa has progressed according to an average annual growth rate of 6% between 1983 and 2007.

Read also Marine Turtle

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