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 Post subject: Turtles say ‘hello’ to our shores
 Post Posted: Tue Oct 04, 2005 2:53 am 
Turtles say ‘hello’ to our shores

Nimashi Fernando
DM / Tuesday, October 04, 2005


Five of the seven turtle species visit our shores. A mesmerizing phenomenon.

But who are the five and what do we know about them? I was intrigued to find out. In fact I was so enthusiastic, that I sacrificed one of my leisure-mornings to go in search of Thushan Kapurusingha, a marine turtle specialist, whom I believed, would definitely reveal loads of information.

However, after a more or less difficult quest, finally I did manage to locate Mr. Kapurusingha, who is also the project leader and committee chairman of the Turtle Conservation Project. (TCP). He did have a lot to say about turtles. Quite an interesting lot of facts they were.

Turtles are a group of cold-blooded tetrapod fauna, basically spending most of their time in the oceans (see classification). Their forelimbs have modified to flippers.

All turtles invariably consist of a tail, a carapace (the top shell) and a plastron (the shell underneath). The male turtles have longer tails and also claws on each of their fore flippers which are used to clutch on to the female during the mating episodes.

Turtles cannot withdraw their head and limbs into their shell, like the tortoise. A turtle is near-sighted but can see all visible colours and orange in particular. It has no external ear lobes or teeth in its mouth.

However, it has an acute sense of smell which enables it to detect prey even in murky waters of the rough and disturbed sea. Ecologically, marine turtles are important for maintaining the growth and recruitment in sea grasses. They feed on sea grass crops, which in turn regulate growth(the dugongs also crop sea grass). Sea grass beds are very important in terms of serving as breeding grounds and dwelling places for many sea fauna, not forgetting its productivity in marine ecosystems.

Turtles are considered as keystone species. If they are removed, these habitats will change drastically.

Also another interesting anatomical feature is that they possess salt glands, a gland larger than their brains and located immediately behind their eyes. Although a turtle mostly lives in the ocean, it rarely drinks water. Hence their biological need for water is fulfilled via the food they eat. (fish, jellyfish etc.)

The salt gland is capable of excreting excess salts from the body. The excreted salt in turn, oozes in tiny droplets from openings close to the eye. This phenomenon of its eyes welling up with the liquid, which becomes apparent when it comes ashore to lay eggs, is thought of by residents as shedding ‘tears’.

Turtles have lungs to breath air. They rise to the surface to breath every five to 30 minutes. Since they mostly live in the aquatic environment, they show feeding, resting, mating and migratory behaviour mainly in the sea.

However, they return to the terrestrial environment to nest and occasionally to bask. They have become very well adopted to live in a marine environment over millions of years.

Marine turtles are a successful group of animals that witnessed the rise and fall of the dinosaurs. They came into being 180 to 200 million years ago and have survived to the present. Today, only two families survive, viz Dermochelidea and Chelonidae. The family Dermochelidea is almost extinct. It has only one genus, viz Dermochelys coriacea (the Leatherback Turtles)

Image

All seven species of turtles are endangered. The Kemp’s Ridley, the Hawksbill and the Leatherback are considered as critically endangered. All turtles but the Kemp’s Ridley Turtle (Lepidochelys kempii) nad the Flatback Turtle (Natator deprssus) nest on our shores.

The Kemp’s Ridley lives in the vicinity of the Mexican bay. It is not known to leave the areas and therefore it is considered as endemic to that area. Also, Kemp’s Ridley is the rarest among the seven species.

The Flatback Turtles are considered endemic to the Australian region , they are not known to leave that particular continental shelf. (a continental shelf is different from a continent. The Earth’s crust is composed of continental shelves and the continents and the oceans reside on these shelves.)

The five species that nest in the Sri Lankan coasts:

The Green Turtle (Chelonia mydas)
Local name: Gal kesbewa


They grow to an average length of 1m and can weigh up to 230kg. They are migratory and can be found in the tropical Indian, Atlantic and Pacific oceans. The popular delicacy ‘turtle soup’ is made of the flesh of the green turtle. The charasterieric green colour of the tissues underneath its top shell, have rendered its peculiar name. The adults are herbivorous, hence they feed on marine vegetation.

The Loggerhead Turtle (Caretta caretta)
Local name: Olugedi kesbewa


They grow up to 1m in length and weigh up to 180kg. They nest in tropical beaches and also in some temperate locations. Loggerheads are primally carnivores, and the name ‘Loggerhead’ refers to the large head with muscular jaws, ideal for crushing prey.

Loggerheads are the rarest in Sri Lanka.

The Hawksbill Turtles (Eretmochelys Imbricata)
Local name: Pothu kesbewa


They are relatively small, growing up to 90cm and weighing up to 50kg. They inhabit tropical coastal waters and are carnivores. Hawksbill gets its name ascribed to the narrow bird like beak, which is used to catch animals hiding in small crevices. They have a beautiful elaborate shell, which renders its Sinhala names.

The Leatherback Turtle (Dermochelys Coriacea)
Local name: Daara kesbewa


They are the largest of all turtles and grow up to a length and weight of 3m and 600kg, respectively. Leatherbacks exclusively feed on jelly fish.

All turtles have a hard carapace. But in the case of the Leatherback, the carapace is covered by an additional leathery skin. Hence that explains its English name. Also it has ridges along its back (5 or 7), which accounts for its Sinhala name.

The Olive Ridley (Lepidochelys olivacea)
Local name: Batu kesbewa


The smallest of all. The adults weigh lesser than 40kg and measure up to 65cm in length. They can be found in coastal waters of the tropical parts of the Indian, Pacific and Southern Atlantic ocean. They are omnivorous. Hence,they feed on crustaceans, fish and some marine vegetation.

The nesting ground of these turtles are mostly concentrated along the belt of the western, southwest southern and southeast coast line of Sri Lanka. However, turtles do visit beaches in Northeast Tricomalee and Nilaweli, but they are not considered as routine nesting grounds.

There are many a tantalizing facts, figures and phenomena governing the biological process involved in the breeding scenes of these vulnerable creatures. Everything commencing from the event of a female crawling to the beach to lay eggs after mating with so many males, to the events of the hatchlings crawling to the oceans in the dark, is quite awe inspiring.

Classification
Kindom: Animalia
Class: Reptillia
Order: Chelonia
Families: Chelonidae and Dermochelidae

Pictures courtesy T. Kapurusingha


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 Post subject:
 Post Posted: Mon Mar 31, 2008 6:41 pm 
wow, this has been a spectacular thread. i just love turtles so much! i've basically become a turtle expert myself nah, well, just kidkidding. those are so huge, its unbelievable!
jason


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