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GREEN TURTLE CHELONIA MYDAS
Mary Harrison© 2003
Guernsey had a rare visitor to its shores, a Green turtle (Chelonia mydas) was found on Grandes Rocques beach by Mary Harrison on Monday 13th January 2003. Its believed to be the first live Green turtle recorded hauled out in British waters. The turtle was suffering from hypothermia and was taken to the Guernsey Aquarium where she was looked after by proprietor David Miller and local veterinarian John Knight with assistance from the GSPCA. The ambient sea temperature was 9șC when the turtle was discovered but the species enjoys temperatures of a minimum of 9șC. The aquarium gradually raised the water temperature, she then started to signs of recovery and was eventually fit and well enough to be trasported to a special rehabilitation centre in Gran Canaria thanks to the help of a variety of people and organisations including; the QUrium; the GSPCA; vet John Knight; Specsavers (who kindly loaned their new Kingair 350); Tom Scott; Mary Harrison and the Marine Section. Special thanks must also go to Rod Penrose of Marine Environmental Monitoring in the UK and Peter Richardson from the Marine Conservation Society who flew over to help provide expert advice. Finally a big thank you to Gran Canaria veterinarian Pascual Calabuig and his team at the rehabilitation centre who agreed to take GT1. Pascual's expertise in this field and facilites offered by the Institute proved invaluable.
DNA SAMPLES TAKEN The Turtle was micro-chipped and DNA samples were taken to try and determine the origin of the turtle. The results, which were tested by Angela Formia at the University of Wales, Cardiff were incinclusive. She sequenced a 489 base fragment of the mitochondrial DNA to obtain a haplotype that could be compared to those found by previous studies among nesting females in the Atlantic and Mediterranean. In fact, mitochondrial DNA sequences (being maternally inherited) can be used as genetic tags and may help in determining the rookery of origin of individuals (in practice, due to their low variability they are more useful in defining origin on wider regional scales). However, the haplotype of the Guernsey turtle did not match any others previously described in Atlantic or Mediterranean nesting populations. Instead, to Angela's knowledge it has been found to occur only among a nesting population in the Indian Ocean (Comoros) and among individuals captured at sea in the Atlantic (Central Africa and one juvenile stranded in Scotland). It must be noted that not all nesting populations in the Atlantic and Mediterranean have been described to date. It is likely that, as new samples are obtained and more rookeries are genetically surveyed, this haplotype will be found to occur in Atlantic nesting populations. It is nevertheless interesting that its geneticcharacteristics make it highly divergent from sequences described to date and there is no evidence that it may be more related to Mediterranean or Atlantic haplotypes. Angela will repeat the analysis in order to double check these entire results, but meanwhile suggests that release of the stranded turtle cannot be guided by its genetic characteristics.
WHY IS IT CALLED A GREEN TURTLE? The green turtle is so-called due to the colour of its fat tissue. The shell or carapace varies in colour from olive-brown to tortoiseshellbrown (similar to a Hawksbill turtle).
HABITAT, DISTRIBUTION AND MOVEMENT Green turtles inhabit three types of habitat, namely: high-energy oceanic beaches; convergence zones in the pelagic habitat; and benthic feeding groundsi n relatively shallow and protected waters. The green turtle is found throughout the world in all tropical and sub-tropical oceans. In the United States, Atlantic green turtles can be found around the US Virgin Islands, Puerto Rico, and continental US from Texas to Massachusetts. Important feeding areas include the
Florida Keys. Major Atlantic green turtle nesting
colonies are located on Ascension Island, Aves Island,
Costa Rica and Suriname. There
DIET AND SIZE The young are carnivorous (eating species such as cuttlefish and jellyfish). However, when green turtles move to the shallow feeding grounds they are herbivorous feeding on sea grasses and algae instead. Green turtles are the largest of all the marine turtles and can grow to a weight of over 200kg and length of over 100cm. The carapace of the green turtle discovered in Guernsey measures 75cm by 58cm.
REPRODUCTION The female green turtle lays its eggs
at night. As many as seven clutches are deposited at
12-14 dayintervals, an average clutch size being 110-115
eggs. The nesting process takes an average of two hours.
The eggs are then buried in the sand to try to protect
them from predators. One recent interesting discovery is
that temperature of the eggs during incubation determines
the sex of the hatchlings. Eggs incubated below a pivotal
ENDANGERED SPECIES The green turtle is listed as an
endangered species by the International Union for the
FOR FURTHER INFORMATION ON TURTLES, VISIT THE FOLLOWING WEB SITES
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IMPORTANT NOTICE This web-site is protected under international copyright laws and is the property of Carol Medder. Any unauthorised copying or transmission of its contents in full or in part is prohibited without prior permission of the author. Schools, colleges and universities are allowed to use the contents for educational purposes. C.Medder1990/2015©
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