How about some introductory text here about turtles.
Turtles are reptiles, a class of vertebrate animals that has survived for more than 200 million years, through stable periods and times of extreme environmental change. Reptiles evolved from amphibians, an even earlier class of vertebrates that lives on both land and in fresh water. Over time, the reptiles came to dominate the Earth; on land, in fresh water and the seas, and in the air. But it was early in the history of reptiles that turtles, members of the order Chelonia split from the main line of reptilian evolution.
The origin of chelonians is uncertain, but recognizable turtles are known as far back as the Triassic period, at least 180 million years ago when dinosaurs were becoming the dominant land animals. Although the Triassic turtles did not look very much different from some modern ones, closer examination would have revealed some characteristics absent from turtles living today. For example, some of the earliest known turtles had teeth rather than sharp edged jaws. Much later, towards the end of the Cretaceous period over 65 million years ago, turtles as large as the 3 meter (9 feet 10 inches) Archelon ischyros lived in the shallow sea that covered much of what is now the western United States.
The fossil record and chemical evidence in some rocks show that the Earth
underwent some drastic changes about 65 million years ago which resulted
in the extinction of many groups of organisms on land and sea, including
the dinosaurs. But some groups of turtles survived these changes, and
two suborders remain. One includes the side-necked turtles that retract
their necks into their shells with a sideways motion. Turtles in the other
more diverse suborder, which includes sea turtles, retract their necks
straight in. The sea turtles of today belong to two families, the Dermochelyidae,
which has a single species, the Leatherback
turtle (Dermochelys coriacea); and the Cheloniidae,
which has two subfamiles, each with two genera and three species. The
subfamily Chelonini includes Green
turtles (Chelonia mydas), flatback turtles (Chelonia depressa),
and Hawksbill turtles (Eretmochelys
imbricata). The subfamily Carettini includes Loggerhead
turtles (Carette caretta), Olive
Ridley turtles (Lepidochelys olivacea) and Kemp's
Ridley turtles (Lepidochelys kempii). Although sea turtles
have not changed much for a long time, the slow process of evolution will
continue unless we, through neglect, cause them to become extinct.
Turtles are reptiles, a class of about 6,000 vertebrate species that have scaly skin, breathe air and use sunlight to heat their bodies (ectotherms). Like all reptiles, turtles reproduce through internal fertilization and, like most reptiles, lay their soft-shelled eggs on land.
One unique feature of the turtle is its shell. This protective skeletal structure is an armored enclosure for the soft vital internal organs. The upper part of the shell, called the carapace, is covered with large scale-like structures known as scutes. The carapace is connected to the underside, called the plastron, by hard-shelled plates known as lateral bridges.
The large-sized body cavity of turtles, especially sea turtles, contains bulky intestines needed for digesting vegetation and small sea creatures. The green sea turtle, which is primarily vegetarian, has a unique feature in its digestive system. A specialized part of its digestive tube contains bacterial symbionts which aid in digesting cellulose. Only a few other reptiles are primarily vegetarian.
The large body cavity also enables the female turtles to produce and hold a large volume of eggs. Female sea turtles are also capable of storing live sperm for several years, although fertility decreases over time. This enables the female to fertilize numerous clutches of eggs without having to mate.
In addition to using their lungs for breathing, turtles have developed supplemental forma of respiration. Some aquatic turtle species bring water in through their nasal passages and into their mouths and throat where oxygen is extracted by the pharynx. This is done through the pharyngeal lining which acts as a gill. Some turtles take water into their anal opening where two sacs are filled and emptied with water, causing a slow current which enables oxygen to be collected. One fresh water turtle in Australia has cloacal gills for respiration. Turtles are also capable of containing larger concentrations of carbon dioxide in their blood than most other air-breathing animals, therefore, they are able to use their oxygen supply very efficiently over a long period of time. Both blood and muscle tissue can store oxygen in large quantities, helping the turtle to remain underwater for long periods of time.
Another aspect of the turtle respiration is the need for exterior flexibility. The hinged plastron allows for some contraction and expansion of the chest cavity. In the case of sea turtles, breathing becomes more difficult when the females come ashore.
They drag their bodies from the sea onto the beach to lay their eggs in the sand. The hundreds of pounds of body weight against the sand makes breathing more difficult than in the water.
Sea turtles have specialized adaptations for their marine existence.
Their shells are greatly reduced in weight and streamlined in shape to
reduce water friction. Front and rear flippers replace the stumpy legs
of land turtles and contain well-developed muscles for swift long distance
travel. Sea turtles have been known to move through the water at speeds
up to 35 miles per hour. These adaptations have been refined over millions
of years of evolution and environmental changes.
In order to effectively manage and protect the sea turtle populations, we have to know where they are and what hazards they have to overcome. Traditionally, researchers' possibilities have been restricted to nesting beaches, the eggs, or hatchlings. The portion of time a sea turtle lives on the beach is very short. All their existence is essentially marine. However, the terrestrial phase of their lives is necessary for the continuation of the species, and this period is perhaps the most vulnerable for the marine turtles. To understand them and to prevent their extinction through management of the population, we have to determine their migratory and foraging cycles. In more general terms, we have to know what they do while they live in the sea.
There are several tagging methods for the marine turtle, which are used to later determine their movements. Tags such as tissue transplant, known as "living tagging", can be applied. The marginal marking of shells or notches, can also be utilized to identify a group. To identify individuals, numbered tags can also be used, including metal or plastic tags, or the leading edge technology of Passive Integrated Transponder (PIT), which is inserted in the juvenile's muscle. The records of tagged individuals through any of these methods, can provide only point movements. The qualities revealed by this type of tags have much value in determining reproductive characteristics on the nesting beaches, long distance movements, etc., but often these are nothing more than initial and final points, with one or two years of unknown data in between these two points.
It can also be possible that the location in which the mark was made
is a very distant point, in time and space, from the final point, not
revealing how the turtle arrived there. To determine long distance movements
and estimate the negative impacts suffered by the marine turtles in the
sea, satellite telemetry has been adopted. Many animal species have been
tracked by means of radio transmitters capable of sending a signal to
a satellite. Through satellite studies we can determine migratory routes,
swimming, breathing and diving behavior, winter feeding locations, and
The Loggerhead (C. caretta gigas) turtle set a mark in 1994 when the first transpacific movement was confirmed, when a plastic mark was returned from a female that had been captured and raised in captivity in Bahia de los Angeles, Baja California, Mexico, and which after being released in Baja California, was captured in Japanese coastal waters. From that moment, a series of studies began, based on satellite tracking, and one adult turtle raised in captivity was monitored during 368 day period from August 10, 1996 to August 12, 1997. During this time the turtle migrated throughout the Pacific Ocean, covering over 11,500 km between Santa Rosalita, Baja California, Mexico and Sendai Bay, Japan. This suggests that upon reaching their sexual maturity, the camagua or loggerhead turtle is capable of migrating from Baja California to the beaches where it was born in Japan.
Through genetic analysis and satellite telemetry, we now know that the majority of the black turtles (Ch. m. agassizii) in the area of Loreto, South Baja California, Mexico, come from the nesting beaches in Southern Mexico (Michoacan, Guerrero, and Oaxaca), performing seasonal migrations between the foraging grounds in the Gulf of California and their nesting grounds. The actual tracking of a Leatherback turtle (D. Coriacea) nesting in the coastal waters at Agua Blanca, Southern Baja California, indicates that at the end of the nesting season, the turtle started a pelagic trip in a southbound direction. However, we lack additional information, since the project has not been completed.
In 1998, in the Yucatan Peninsula, 4 transmitters were deployed on carey (E. imbricata) female turtles that nested on the beaches at Las Coloradas, Rio Lagartos, Yucatan. All four specimens have followed similar patterns, heading towards the same zone, between 150 and 200 km to the west, in the Gulf of Mexico, to the Northeast point of land at Progreso, Sisal, and Celestun, between 21 and 22 degrees north latitude and 89 and 91 degrees west longitude, and between depths of 10 and 20 fathoms. The Madagascar and Banco Ingles reefs are located in this area, which is a very well defined nesting site, although in general this is an area of seagrass with a coral seabed, and quite possibly with abundance of sponges.
At this time, there are no satellite tracking studies in the State of Veracruz. This project being undertaken by ORF and researchers at the Lechuguillas turtle camp is considered to be the first such research related to the tracking of sea turtles in this area. Since 1994, the CRIP-VER began a program to study and protect sea turtles in Lechuguillas, Veracruz, Green turtles (Ch. mydas), Kemp's Ridley turtles (L. Kempii), loggerhead turtles (C. caretta) and carey turtles (E. imbricata) have been reported to nest along the 17 kilometer stretch of protected beach. In 1998, the only confirmed nesting site of leatherback turtle (D. coriacea) was reported in the area, and the green turtle constitutes the species that nests more frequently. When the camp site starts its activities, the tagging program begins, utilizing serialized monel steel tags with the inscription: INFORMAR (INFORM) PESCA-CRIP-MANZANILLO COLIMA, MEXICO.
A total of 861 tags have been placed on Green turtles (Ch. mydas)
since that date, employing tag series J, K, AM, BA, BE, KA, and FB. No
report has been received to date from other states or countries. The above
facts would lead us to think that turtles remain in the area. Although
personal conversations with local fishermen indicate that during the nesting
season, turtles are seldom captured. This leads us to the following questions
in regard to adult turtles: Where do they go after the nesting season?
Where do they stay? Satellite tracking of Green turtles nesting at Lechuguillas,
Veracruz, will provide valuable knowledge on distances, possible migration
routes after the nesting season, and sites where they stay. The data obtained
after tracking the migration of these two turtles will contribute to our
knowledge of their behavior in open sea.
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