Marine turtles

Vazquez, G.F., M.C. Reyes, G. Fernandez, J.E.C. Aguayo, and V.K. Sharma. 1997. Contamination in marine turtle (Dermochelys coriaca) egg shells of Playon de Mexiquillo, Michoacan, Mexico. Bull. Environ. Contam. Toxicol. 58 326-333. 

Toxic marine turtles may cause a type of poisoning about which little is known. However, the cases reported bear witness to its serious nature. While most species may be eaten without fear, in the tropical parts of the Pacific, particularly around the islands of Japan, some turtles may become extremely toxic. 

The application of high-sensitivity ICP-MS detectors coupled to HPLC has enabled the detection of trace arsenic compounds present in marine animals. Thus, arsenocholine has been reported as a trace constituent (<0.1% of the total arsenic) in fish, molluscs, and crustaceans (37) and was found to be present in appreciable quantities (up to 15%) in some tissues of a marine turtle (110). Earlier reports (46,47) of appreciable concentrations of arsenocholine in some marine animals appear to have been in error (32). Phosphatidylarsenocholine 45 was identified as a trace constituent of lobster digestive gland following hydrolysis of the lipids and detection of GPAC in the hydrolysate by HPLC/ICP-MS analysis (70). It might result from the substitution of choline with arsenocholine in enzyme systems for the biogenesis of phosphatidylcholine (111). 

The shells of terrestrial tortoises and freshwater turtles have also been used in some of the same ways as the larger marine turtles. Whole turtle bodies, with the soft tissue and most of the skeleton removed, have been made into pouches and specialized containers for personal and ceremonial use. 

Tortoiseshell is the name given to the mottled, golden or reddish and brown, translucent, homy plates or scutes covering the shells of certain species of marine turtle. The best known and by far the finest tortoiseshell comes from the hawksbill turtle, but the scutes of the green and the loggerhead turtles have also been put to some decorative uses. 

Although marine turtles are constantly being researched, our knowledge of them is somewhat limited as, from within minutes of hatching, they live their entire lives in the sea. Only the females come ashore to lay their eggs, after which they return quickly to the sea (Fig. 8.1). It... 

A marine turtle can lay up to 800 e gs in one season, in batches of 90 to 150. The e hatch about nine weeks after they hove been laid. The baby turtles (the hatchlings) emerge at night and make their way strai i into the sea, attracted by the celestial li t shinir on the surface of the water. 

Marine turtles have bony shells and belong to the family Cheloniidae. Unlike tortoises, the marine turdes have flippers in place of legs, and cannot retract their heads and tails into their shells. 

Marine turtles have been around since the earliest dinosaurs, but having survived for 200 000 years they are now under threat of extinction. Their natural predators are many and varied. Some predators eat the turde eggs before they are hatched, some eat the tiny hatchlings, and there are plenty more creatures that will eat a young turtle in the sea. But their worst enemies are humans. 

Today some countries still allow fishing of hawksbill turtles for their shell, though thanks to closed seasons and other types of management, the amount fished is greatly reduced. Most of the CITES signatories respect the total ban on the international trade of marine turtles or their parts. Thus, although it may be possible to purchase items made from tortoiseshell in, for example, the Far East, it is not permissible to import them into Europe, America, and many other countries. 

Marine turtles have primarily been a source of protein eggs and meat. To local populations in the areas where turtles lived these were part of their everyday diet, and the skin of the flippers, neck and tail also made excellent leather. 

Although there are no illustrations in the tombs of ancient Egypt of tortoiseshell in use, there are pictures of marine turtles, and it is thought that the material was used for decorative purposes, for example knife handles or bracelets. Like horn, tortoiseshell does not survive the passage of time. 

In turtles, the shell is the most unique feature. The lightweight, streamline shape of the shell forms a protective enclosure for the vital organs. The ribs and backbone of the turtle are securely attached to the inside of the shell. The upper part of the shell, the carapace, is covered with horny plates that connect to the shell s bottom, the plastron. Extending out from the protective shell are the marine turtle s legs, which have been modified into paddle-like flippers capable of propelling it at speeds of up to 35 miles... 

Hg residue data on reptiles, birds, and mammals are presented in Table 8. Only four studies on reptiles in Mexico have been published, and all of these were on marine turtles. The levels found in these turtles ranged from 0.795 pg g" dry wt in liver of Lepidochelys olivacea to 0.0006 pg g" dry wt in blood of the same species. When Hg was measured in liver and kidney, these organs displayed the highest concentrations. It has been observed tliat in marine reptiles Hg seldom exceeds 0,5 pg g" dry wt (Eisler 2010) such is the case also with reptiles sampled from Mexico s ecosystems (with the exception of liver samples of L. olivacea). 

Mrosovsky, N., 1978, Orientation mechanisms of marine turtles, Animal Migration, Navigation and Homing, K. Schmidt-Koenig, and W. T. 

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