Marine tortoise

The marine tortoises ( Chelonioidea ) are tortoise S present in all the oceans of the world except for the Arctic Ocean.
La Tortue lute is largest, being 2 m long, 1m with 1m50 broad and weighing 600 kg. The intermediate size of the other species goes from 50cm to 1m and is proportionally less broad.

Description

The marine tortoises, like the other tortoises ( Testudines ) are reptiles Ectotherme S having a pulmonary respiratory system, which corresponded to a complete adaptation to the terrestrial life. In supplement of the Kidney S, glands close to their eyes are able to expel the salt surpluses of their blood circulation. Their metabolism is able to support strong concentration of CO₂ at the time of the major divings. They can extract 35 to 52% from the oxygen of their breathing. Their vision is very developed. The eyes are protected by three eyelids, their hearing is particularly fine even if they do not have outer ears, but an internal ear, under an auditive plate. Their sense of smell is on the other hand rather not very powerful. The marine tortoises have one opening excretor, which is also useful for the reproduction.

The sex of the tortoises is not apparent as it are according to their secondary sexual characters as the man can determine the sex of a tortoise. One defined by puberty the period when those appear. Most obvious is the size of the tail, much larger in the males. The size of the claws at cheloniidés in is another. However, these sexual characters are not very marked and certain females can raise them. Only a genetic examination makes it possible to be certain sex of the animal.

See also: Osmorégulation

The carapace

Their flattened carapaces confers better characteristics hydrodynamics to them and plays an obvious part of protection, but certain scientists think that they enable them to store heat. This adaptation, acquired after their return in the seamen circle, enables them to go down very deeply, there, or the temperatures of water are low. N the other hand, they lost their capacity to retract their members there. As for the others watery tortoises, their carapaces is lighter because provided with Fontanelle S. the Dermochelyidae , bulkiest of the marine tortoises, lost besides their scales and their carapaces are covered with a thick leather. Like the other tortoises, they do not moult and know a surface exfoliation partial of the plates corneas of the skeleton.

According to certain theories, their carapace, at least for the tortoise lute, assistance to preserve a sufficient body temperature when she venture in colder water or that they plunge. But this assumption is discussed, owing to the fact that the reptiles, animals with cold blood, are supposed being Poïkilotherme S.

Characteristics

They can swim quickly and several species are capable of speeds being able to reach 35 km/h; with the difference of the fresh water tortoises, they advance by the simultaneous action of the forelimbs.

With the birth, there is in the marine tortoises no external anatomical element which makes it possible to distinguish a sex from the other.

It is thought that certain marine tortoises can exceed the 150 years. One measured a record of 6 hours diving for a green tortoise.

Reproduction

The collective layings of the marine tortoises are called arribadas . They take place on the beaches at the beginning and the end of the lunar cycles when the Marée is with lowest and the weakest undertow.

After several years of maturation, the tortoises can reproduce. The couplings at sea take place near the sites of nesting or during the migrations (between the sites of food and the sites of laying) one or two months before the beginning of the laying.

During the coupling, the male is hung by its two claws former (which are thus secondary sexual characters) to the carapace of the female. The females can preserve the spermatozoa of the males during several months or years in a fold of their oviduct. The females lay only on their birthplace, to a few meters or hundreds of meters near according to the species. It is in general with the favor of the night (a too long exposure to the sun would be fatal for them), in the twilight, often with the rising tide that the females leave to lay on their sand beach of origin. The female can store the spermatozoa to fertilize successive layings. The sex of the young people depends on the temperature during the incubation of the eggs.

They dig a hole in sand with their legs or oars generally back and lay there from 70 to 200 eggs (according to the species) before covering them and turning over to the sea. Some of eggs are not fertilized, the others incubate for approximately two months. As for the other tortoises, the sex of the embryo depends on the temperature of the nest at a certain incubation period. All the young tortoises hatch at the same time and move towards the sea.
Seule a very small portion (approximately 1%) will reconsider the beach which saw them being born because they are the prey the many predatory ones.

Stages of life

According to its age, the tortoise does not nourish itself in the same way and does not live in the same environments. One distinguishes:

the stage egg
the new-born stage: the newborn leaves egg, emerges from the nest in general in group and takes refuge at sea or he swims actively towards the broad one during several days (from three to six according to the species).
the youthful stage Pelagic: this stage begins when the young tortoises give up their behavior of stroke activates and concentrate more on the food while being let carry by the marine currents. The observations at this stage are extremely rare. The behaviors can also be different according to the species. The delivered different ones give rise to think that all the species do not live in the same biotope.
the benthic youthful stage: the youthful ones are sédentarisent on the zones Benthique S (except for the tortoise lute). Their dietary habits seem to change, their predatory too.

the stage sub-adult: he starts with puberty, when the secondary sexual characters appear. The marine tortoises of the same species sexually do not become mature with the same size.
the adult stage: the adults migrate from their zone of life to their zone of laying. All the species of marine tortoises are faithful to their place of laying, with some variations according to the species.

Food

The marine tortoises all are Omnivore S with tendencies more marked towards the plants or the flesh-colored food. Thus, the green Tortoise and the frank Tortue of the Pacific are above all Herbivore S. the Caouanne, the Tortue olivâtre and the Tortue with flat back especially carnivorous and consume Mollusque S, Crustacé S, small Poisson S and other Invertébré S sailors. The Tortue lute is omnivorous and consumes in addition to the Cnidaire S. the overlapping Tortue, it so omnivorous, consumes, like the tortoise lute, of the cnidaires but, is also made rare for vertebrate, Spongivore.

The tortoises must store much energy for their migrations and their layings. For this reason, their food exploits a direct role their fruitfulness. That was shown by corroborating the numbers of layings and El Niño which, by heating water and in their providing more vegetation, increases the number of the migrations later two years, while a cooling lowers the number of the migrations later two years.

Identification of the adults

Easiest to identify is of course the tortoise lute because of its absence of scales. It is also largest of the marine tortoises. The Cheloniidea , as for them, have of a carapace without hull and the scales. When it has more than six pairs of side plates on the backing, it can be a question of a tortoise olivâtre; with five or six pair, it can be a caouanne or a tortoise of Kemp. With four pairs, it is a green tortoise or an overlapping tortoise. One easily distinguishes the caouanne and the tortoise from Kemp by their color; first is red orange and the greenish grey second. One also distinguishes the green tortoise from the tortoise imbricated by the shape of the nozzle and the number of scales préfrontales. The tortoise with flat back has only one claw per fin, of marginal scales sometimes bent to the top, of only one pair of scales préfrontales. One can announce that the tortoise olivâtre and the tortoise of Kemp have four pairs of plates inframarginales, each one bored of a pore close to his posterior edge.

the new-born lute has fins much larger and rough skin, with a réticulée provision of small scales. Its backing is black, with white side peaks while its white drill plate, marbled the brown one clearly.

. They have an extraordinary direction of time and orientation. One think that they are very sensitive to the Terrestrial magnetic field ^, and that it use certainly it for their migrations. One in addition knows that they follow, in their migration the marine currents. Many studies tend to include/understand their migrations for better protecting them.

The fact that the majority of the species return to lay at the place where they hatched, seems to indicate that they memorized the characteristics including magnetic of them.

Predatory

The marine tortoises have natural enemies the such Grand white shark, the Tiger shark and the Requin bulldog as testifies it the scars found on their carapaces, of the dogs and even of the mongeese (on the beaches Virginia) plunders the nests. More still surprising, the eggs of are also directly threatened by the insects and, in French Guiana in particular for the tortoise lute, by the Courtilière. Then the newborns, very vulnerable, leave during the night in general, as soon as the temperature drops. Any rise of the temperature, they stop all activities.

When they emergent of sand, they move towards light signals, usually the waves which flicker with the gleam of the moon or stars), birds, lizard, and with the crabs which are very voracious omnivores. Finally they must reach marine zones more isolated or protected while escaping has a large predation come from the large Poisson S, Pieuvre S or marine birds come to await them.

It was however observed increases at the local level. According to a study made public with Kélonia the August 9th 2007, the population of marine tortoises observed on the island Europa progressed according to a average Annual growth rate of 6% between 1983 and 2007.

Marine tortoises and the Man

Threaten on the marine tortoises

All the marine tortoises are threatened, certain like the tortoise lute being regarded as in critical danger of extinction (red Liste of the UICN). It was common for the tortoises to be driven out with large scales for their meat, lubricates or carapace and the coastal populations always collected eggs of tortoises.

The greatest current threat comes from fishing like accidental catch to the Palangrier and by the Chalut S, in particular at the time of fishing to the Thon. It is estimated that 40.000 tortoises die each year of fishing to the palangrier. According to researchers of the 24e congress on the conservation and the biology of the marine tortoises to the Costa Rica, the tortoise lute is nothing any more but ten years old before extinction if nothing is done to regulate these problems.
Des simple and not very expensive changes like larger hooks or traps whose tortoises can escape can make fall in a spectacular way death rate.

Other dangers are the floating marine Déchets such as given up fishing nets in which they are trapped and drown or the bag plastics which they take for jellyfish S (one their food) and cause digestive occlusions to them.

The tourist development or the urbanization of certain beaches of laying is also a serious threat for the turtles. There thus was a movement to protect these zones from laying, sometimes even by the police force. In certain places as in Florida, after a tortoise laid its eggs, those are collected and replaced in nurseries where they are protected. It is not the best solution because the tortoises return to lay on their beach of origin. Another measurement is the regulation of lightings to prevent that the babies tortoises do not confuse the artificial lights with that of the Moon or the sun on the sea and do not go in the bad direction after emergence.

The black-market of the meat or eggs of tortoise is also a problem in the whole world, especially in India, Indonesia and the coastal nations of Latin America. Estimates give a report on 35.000 tortoises killed per annum with the Mexico and as much with the Nicaragua.

Traditional hunting

On the beaches at the time of the laying, the tortoises are reversed on the back, then in the small hour taken along. But much of tortoises are taken in set nets or drifting. With Haiti the fishermen use devices called " fol" composed of a tablecloth of net with much of slackness. Another device of capture called " bobèche" is composed of pieces of wood pointing out the shape of a tortoise and the unit is covered with draw sheets of nets in which comes to get mixed up the male tortoise which believed to deal has a female.

The chemical threat

The chemical Pollutant S and more particularly metals accumulate in the livers, the kidneys and the muscles of the marine tortoises. This accumulation of pollutant could have a role in the propagation of disease like the Fibropapillomatose.

Degradation

The degradation of the habitats and the coral barrier is a threat for the populations of some.

Protection

The alarmist reports on the populations of marine tortoises pushed the international authorities to consider them in danger of extinction. Since 1981, all the species are registered with appendix I of the Convention of Washington. In spite of that, manpower decrease.

Education campaigns were launched to Mexico and the the United States implying personalities like Jean-Paul II, Dorismar, Los Tigres del Norte and Mana.

Wounded marine tortoises are sometimes helped and looked after by organizations like the Marine Mammal Center in California.

To prevent the accidental captures by the trawlers, American set up a Dispositif of exclusion of the tortoises which makes it possible to limit them.

The breeding

Since the Years 1970, some marine breedings of tortoises were created of which farms integrating of the overlapping tortoises. however these breedings are disputed. Their objectives are quadruple:

To help with research on the tortoises
To provide a framework of discovery so that the general public discovers the tortoises and is sensitized with the environmental problems sailor.
To make slackened.
To sell the scales to make finance the project.

The fourth point is discussed the most, by supporting a trade legal it involves necessarily a parallel traffic of wild carapace of tortoise. In addition, it is very difficult to control if the eggs are wild eggs of plundered nests (" ranch") or obtained continuation the coupling of adults already in captivity (" ferme").

These breedings is generally melted out of closed basin (any attempt out of open basin having failed). Their food, usually very low in calorie, impossible to reproduce in captivity and which involves a slow growth, is modified. It is richer in protein. Water is also heated to increase their growth. If these projects are considered to be necessarily nonprofitable because of the associated costs with maintains the basin, with the medical supervision for all the other tortoise, except those of the overlapping Tortue could economically prove reliable because of the value of its scale. The absence of certainty when with the effect of a relâchage and the possibility of causing epidemics dissuade the governments to support these initiatives. They seem to have closed all.

Recommendations for the observation of the tortoises

To observe the tortoises ( at the time of the laying ) without disturbing them:

to wear black clothing
to remain motionless
not to make a light

Constantly, the tortoise can turn over to the sea if it feels threatened.

It should not be approached before it started to lay. At this time, discreetly (preferably while crawling in sand to avoid the vibrations in the ground which disturbs them) it is possible to approach and light using a red lamp eggs which falls. Even if that appears obvious, it should be recalled that the eggs should not especially be touched. Attention that the tortoise does not see the light. By respect for the other tortoises, to light only the well of laying.

never not to take photographs with flash! This is extremely disturbing for the tortoises.

The small tortoises will leave their eggs two months, with fallen the night later or at daybreak. If you are likely to see an emergence, want not to touch, nor to carry the babies: the friction of sand on their belly enables them to recognize the beach where they were born and especially assistance with the cicatrization of their drill plate (the navel of the tortoises).
Ne not to use a light when the babies move towards the sea, if not they are likely to change way and to move towards you: indeed they are attracted by the sources of light which are normally the reflections of the moon or the sun on water. The fact of making them deviate of their road can be catastrophic (that generates more risks to be eaten or to be dehydrated) whereas only 1 baby for approximately 1.000 arrives at the adulthood, one thus should not still make lower this figure.

The marine tortoises are threatened as of the birth by predatory wheels which catch them with the flight and eat them, by the poaching, industrial fishing, the wandering dogs which eat eggs, the tortoises which in short confuse jellyfishes for plastic bags… by much of events or linked activities to the man.

the marine tortoise is a protected animal: to disturb, to have whole or part of the dead or alive animal is prohibited by the law.

Origin

Oldest fossils of marine tortoises of which we lay out date of 110 My. It is thus thought that, after some 150 My of terrestrial life and tests of colonization of the aquatic environments, of the tortoises gained the sea with all the adaptive characters related to this liquid element. The skeleton became lighter, the members transformed into swimming pallets and out of rudder, the carapace was flattened, the lungs adapted to long apnea, the vision adapted, their neck lost his capacity of retraction in the carapace. The differentiation which was going to give rise to the line of the Dermochelyoidea and the Cheloniidae it is made, at the beginning of this colonization with the Crétacé between 100 and 150 My.

O will polycryptodira |--O Chelydridae `--O Procoelocryptodira |--O Chelonioidea Bauer, 1893, marine tortoises | |--O | | |--O † Toxochelyidae | | `--O Cheloniidae , of which imbricated, green tortoises… | `--O Dermochelyoidea | |--O Dermochelyidae of which the Tortoise lute | `--O † Protostegidae of which Archelon , Santanachelys `--O Chelomacryptodira , i.e. the other tortoises Cryptodires nonmarine

Seven species of alive tortoise:

The taxonomic statute of the frank Tortue of the Pacific is always discussed.

See too

There exists only one tortoise not chélonioidé and which can also live in sea water. Chelodina siebenrocki life in fresh water and ventures in the mangroves.

Taxonomic references

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