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*These primitive vertebrates successfully adapted to life in the sea. 4 groups of Marine Reptiles are SEA TURTLES, SEA SNAKES, SALTWATER CROCODILE, AND MARINE LIZARDS. They live in primarily shallow coastal waters of tropical or subtropical oceans, but some turtles move into cooler waters to search for food.

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*The reptiles are usually restricted to warmer waters because they are cold blooded and depend on the external temperature of the water to control their metabolic rates. Their biochemical reactions slow down in cooler water.

 

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*Marine reptiles are equipped with SALT GLANDS which remove excess salts (unlike their land and freshwater relatives). In lizards and turtles, these glands are above the eyes and can secrete a concentrated salt solution which end up bathing the eyes

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*This removes excess body salts, the tears cleanse the eyes. The ability to pump out the excess salts varies and determines which environment the organism can live.

 

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*Marine Lizards

Only one marine lizard exists and is the Marine iguana (Amblyrhynchus subcristatus) which lives in large colonies on the Galapagos. They have become secondarily adapted to marine life. They spend most of their time basking in the sun on warm rocks along the shore, warming up after swimming in the cold water to eat seaweed.

 

 

 

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*Adaptations Flattened tail for swimming (like snakes)/ webbing on all four feet /powerful claws to anchor in heavy seas / salt glands to get rid of salt taken in while eating macrophytic marine algae (seaweed) / can regulate buoyancy by expelling air and / develops BRADYCARDIA, a marked decrease of heartbeats per minute in response to diving (from normal 43/min to 7-9/min).

 

 

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*The marine iguana derives nourishment exclusively from sea flora and subjects itself to considerable exertion during its feeding dives, and though they can stay under for a considerable amount of time, they usually spend most of the day on the lava boulders along the shore.

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*This probably has to do with the animal being cold blooded and loosing its heat to the surrounding water quickly. It props itself up on the rocks to absorb heat. (temp. tolerance from 21C (70F) to 49C(120F).

 The marine iguana populations appear to be flourishing unlike the land iguanas which are under considerable stress from introduced animals.

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*Saltwater Crocodile (Crocodylus porosus) inhabits mangrove areas and estuaries in the eastern Indian Ocean, Australia and some western Pacific Islands, and while most live on the coast, they are known to venture into the open sea. The largest is 30' but usually are 20'. They are very aggressive, eat people etc.

 

 

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*SEA SNAKES

There are about fifty kinds of sea snakes with most occurring and probably evolved in warm south Asian and Australian coastal waters. A few species are found as far away as Japan and the Persian Gulf. One, the yellow-bellied Pelamis, has crossed to the tropical Americas west coast and lives by the millions in the bay of Panama.

 

 

 

 

 

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*While sea snakes differ in form and behavior, there are a few features in common. They have flattened, rudder like tails, nostrils set on the top of the snout instead of on each side and equipped with flaps to keep them closed underwater, and smaller size of the broad belly plates that land snakes use in crawling. They have a gland in the mouth that helps get rid of salt from the seawater they drink.

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*They have only one lung like most snakes but it is very long, lined with blood vessels to aid in O2 absorption and at the end is a simple sac to store air. Controlled heartbeats, BRADYCARDIA, reduces pulse rates by 50% when under water. Diving time varies with species, activities and water temp. The more active the less time under and the warmer water decreases diving times.

 

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*Reproduction: Sperm is implanted into oviducts of the female and she can store these for weeks or years until the eggs are ripe, fertilization is in the oviduct and many species have the embryo develop there and are born alive. Most are ovoviviparous and have no need to come ashore but a few do to lay eggs

 

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*Olive sea snake...unmarked mustard yellow skin Aipysurus laevis up to 6', large mouth and blunt cobra head and dark cobra eyes. Its a fish eater and with cannot catch fish unless it corners them in a crevice...would die in a fish tank with free swimming fish.

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*Yellow bellied -Palamis platurus -gulf of California to Ecuador is equipped with fangs in the front of their upper jaws which to inject their potent venom.. They float on the surface attracting small fish to it like a piece of wood drifting in the water.

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*Sea snakes are related to the cobras, and are the most venomous of all snakes though they are not very aggressive. A large number of humans ..Asian fisherman mainly, have died from sea snake bites..some of which possess venom many times more powerful than any land snake. They do have short fangs and small heads and some won't bite even when provoked, but bites and fatalities do occur.

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*The bite is painless but after several hours the legs of the victim become paralyzed, his eyes close and jaws lock. He may live for several days before convolutions and respiratory failure bring death.

Apart from Asians who eat sea snakes, sea eagles are known to feed regularly on the reptiles, seizing them when they come up for air, grab them and drop them on the rocks.

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Sea snakes of several different species belong to a group related to the cobras but are aquatic rather than land dwelling. They are only moderately large, rarely exceeding 2 m in length, often with peculiarly small heads for their body-size. The body is compressed as an adaptation for swimming and the snakes are so thoroughly aquatic that they are either clumsy or helpless when brought ashore.

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Only genus Laticauda has the typical broad ventral scales of snakes, and it is often considered the least advanced of the sea snakes. Nevertheless, similar to cetaceans, their lungs still require them to surface occasionally to breathe.

Sea snakes are venomous. They have short hollow fangs near the front of the upper jaw, and the poison acts on the nervous system like the related cobra's. Unlike land snakes, however, sea snakes are not inclined to bite, and as such are not harmful unless abused.

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Sea snakes have a less efficient venom injection apparatus as compared to vipers or cobras. Antivenom is not available commercially.

Sea snakes are confined to the tropical oceans, chiefly the Indian ocean and the western Pacific ocean. The yellow-bellied sea snake, Pelamis platurus, extends to the eastern Pacific. The olive sea snake, Aipysurus laevis, tends to live in reefs.

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Sea kraits are a type of sea snake. Sea snakes are divided into two subfamilies, laticaudinae and hydrophiinae, with the former distinguished from other sea snakes by the fact they are amphibious (living on land and water), rather than aquatic (never leaving the water). Sea kraits are ovoviviparous, returning to land to lay their eggs, versus other viviparous species that bear their young in the water (subfamily hydrophiinae, aquatic sea snakes).

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Amphibious sea kraits, members of subfamily laticaudinae, have specialized ventral scales for crawling on land. Unlike eels, sea snakes are reptiles and have scales. This one is about 18 inches (46 cm) in length.

All 50 or so species of sea snakes are venomous, and some are known to have venom ten times as strong as rattlesnake venom, making them among the most potentially dangerous of all animals. Fortunately for divers, they have short fangs and are usually quite docile.

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. A sea snake's paddle-shaped tail is useful for swimming, but otherwise these reptiles look very much like their land cousins, even down to the forked tongue they use during their searches.

Most cases of people being bitten by sea snakes involve fishermen bitten when sorting through a catch from a net. The venom is composed of powerful neurotoxins (affecting the nervous system) and sometimes myotoxins (affecting skeletal muscles), with a fatal dose being about 1.5 milligrams. Most sea snakes can produce 10-15 mg of venom.

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*SEA TURTLES

Class: Reptilia Order: Chelonia Family: Cheloniidae

Sea turtles have been hunted for meat, eggs, shells, leather, and decorative objects and are now becoming victims of pollution. While they are relics of the past, they aren't obsolete nor predestined for extinction. They are beautifully adapted for life at sea and are found in most ocean habitats.

 

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*They are strong swimmers and protected from predators by size and shell. They can stay under for a long time and some can live in salt water without ever having to drink fresh water. These adaptations make them slow and vulnerable when they leave the sea to lay eggs on land, the only time they have to leave the sea.

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*Characteristics: Non-retractable heads and limbs. They have powerful paddle-shaped front flippers to swim and hind fins are used for stabilizing and steering, shells are streamlined and flattened top to bottom to decrease water resistance, fatty deposits and very light spongy bones increase buoyancy enabling them to float easily. (green fat in green turtle.)

 

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*There is little or no competition between the species.

Feeding: Most turtles feed in shallow coastal waters (food extremely abundant) . The green turtle feeds on meadows of turtle grass (Thalassia) throughout the tropics.. the carnivorous turtles, loggerheads, feed on crabs, shellfish, sponges, fish, and horseshoe crabs.

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*The hawksbill can pry mussels off rocks and also eats clams, jellyfish and algae. The Pacific Ridley feeds on sea urchins and other inverts. living in eel grass beds. The leatherback feeds on jellyfish far from shore and is equipped with a mouth lined with sharp spines to hold its prey and a digestive system adapted to withstand the stings.

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*Its also the largest of the sea turtles and are the only turtle whose shell is covered by a leathery skin and whose backbone is NOT fused to the carapace

 

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*         Atlantic Leatherback: Dermochelys coriecea

         Distribution: Tropical, Temporal and Sub-arctic Oceans

         Color & Description: Black or brown (no shell) leathery skin, no plates on shell and no scales on its head or body. The top shell has seven ridges which run lengthwise.

         Adult Weight: 700-1,600 lbs.

         Diet: Mainly Jellyfish, also sea urchins, octopus, tunicates, crustaceans, fish, algae.

         Habitat: Open ocean, bays, estuaries

         Other: Only turtle known to be warm blooded and capable of maintaining body temperatures near 82"F. (even in 45' water)

         Status: Endangered

See UNat. article the Leatherback

 

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*         Atlantic Loggerhead: Caretta caretta

         Distribution: Subtropical, Nova Scotia to Argentina, Caribbean, Gulf of Mexico.

         Color: Red or Brown

         Weight: 250-400/1000 to 1200 lbs the largest of the hardshell turtles.

         Diet: Mollusks, sponges, jellyfish, squid, barnacles , crabs, fish, seaweed.

         Habitat: Open ocean, estuaries, bays, mouths of rivers...brackish waters.

         Reproduction: 1. Nests above high water mark on open beaches

         2. April to October

         3. Avg. clutch 120 eggs.

         4. Incubation- 55-70 days Status: Threatened

 

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   Green Turtle: Chelonia mydas

         Distribution: Tropical Oceans except east Pacific.

         Color: Light and dark brown, olive green, bluish black

         Weight: up to 850 lbs.

         Diet: Algae, turtle grass Thalassia (young feed on jellyfish, mollusks and crustaceans)

         Habitat: Open oceans, estuaries, and in summer, sounds and rivers.

         Reproduction: 1. May nest several times in a season.

         2. Avg. clutch 70-140 eggs.

         3. Very sensitive when emerging to nest.

         4. Nest during night

         Other: Undergo long ocean migrations and have been observed sunning themselves in the tropics.

Status: Endangered

 

 

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*         Hawksbill Turtle: Eretmochelys imbricata

         Distribution: Tropical oceans near coral and rocky reefs.

         Color: Amber streaked with red, yellow, brown and black

         Weight: 80 - 280 lbs.

         Diet: Young eat plants, adults eat jellyfish, coral, sponges, mollusks, sea urchins, fish (omnivorous).

         Habitat: Oceanic and coral reefs, some lagoons and estuaries

Status: Endangered

 

 

 

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*         Ridleys: Lepidochelys kempi

         Distribution: Tropical oceans

         Color: gray to olive green

         Weight: 100 lbs

         Diet: Crabs, jellyfish, snails, clams, fish.

         Habitat: Shallow waters, mangrove habitats.

Statue: Endangered

 

 

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*Migration: Without any landmarks to guide them, some sea turtles swim a thousand miles or more across open oceans to lay their eggs on tiny island beaches they have not been to since they were hatched 10-50 years before. Their powers of navigation bring them back to their ancestral nesting areas every 2-4 years.

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*Migratory routes have been studied by tagging adults at nesting site. When they approach their nesting sites, usually small desolate beaches with few terrestrial predators, they remain offshore and mate. Its possible that the developed eggs in the female have already been fertilized and that this mating is for future eggs. The sperm can be stored from 2-4 years.

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*Nesting

While the males wait offshore, the females swim through the surf and crawl up on the beach and begin to dig their nests with their front and hind flippers, often flinging sand into their eyes. This is washed out by their salty tears.

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*Using the hind flippers, a cylindrical egg chamber is scooped out and about 100 eggs are deposited. They are covered with sand to protect them 1. from land crabs gulls and rats and 2. from drying out.and 3. keeps them at the right temperature. Females may repeat this up to five times during the summer breeding season (500 eggs total) before returning to the feeding grounds.

 

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*Hatchlings

After 60 days the baby turtles (2oz) scamper towards the sea equipped with about a weeks supply of yolk. They head toward the faint glow of the rising sun to locate the ocean, hatching at night. Instincts drive these hatchlings towards the lighter horizon so if they emerge during the day, all types of problems follow ,not to mention the frigate birds and buzzards feeding on them.

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*For years the most popular explanation has been that turtles smell their way back to their natal beaches. It is believed that hatchlings can imprint on distinct chemical characteristics of the beach and years later, when they reach breeding age, remember and retrace trails of these chemicals carried by ocean currents.

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*The population of green turtles was studied in this effect. They migrate between their feeding grounds off the coast of Brazil and nesting grounds on Ascension Island, midway between south America and Africa...a 2800 mile round trip.

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Many years of tagging show that adults of some species go back to the same beach and sometimes almost the same spot on that beach to lay eggs. Establishing that those adults (or any adults) were hatched there, will require tagging of a hatching and seeing that the same turtle comes back when it is sexually mature...10-50 years later.

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*Why adult turtles would return to their natal beach is another story. They presumably make long-distance journeys to get to habitats they need during only part of their life cycle. Herbivorous green turtles, for example, feed in calm, shallow coastal waters but need steep, sandy beaches to get above the high tide line when it is time to lay their eggs

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*. Because these habitats are often nowhere near one another, migration during the breeding season makes sense. HOWEVER, some green turtle populations appear to swim by and ignore perfect nesting beaches while making their long migration. Its possible that geological and biological factors we can't see are important.

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* Example, a wide current moving away from Ascension Island probably carries the vulnerable, planktonic (drifting) hatchlings quickly away from the coastal predators.

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*This little extra in terms of survival and reproductive success could be worth the extra thousand(s) miles of migration. ALTERNATIVELY, some migratory routes may be vestiges of ancient behavior no longer adaptive.

 

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*Perhaps small distant islands were once larger or closer together than they are today and with the spreading sea floor, turtles nesting on islands once only a few miles from shore...attractive because of the lack of egg-eating predators...were gradually forced to swim farther and farther out to sea.

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*Research has shown in the case of the green turtles, that the current going past Ascension Island, sweeps right into the faces of those turtles grazing in the feeding grounds off Brazil. Also its been established that turtles have a well developed nasal epithelium and excellent olfactory acuity

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*Even if this olfactory imprinting does turn out to be what governs the sea turtle migration, the mechanism is an imperfect one because turtles often colonize new nesting habitats, which would be essential for the species to survive because beaches only last for 100, 1000, or 10,000 years but the turtles have been around for 100million years!

 

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*Problems

In 1947, more than 40,000 Kemps Ridley sea turtles came ashore in a single day to lay their eggs on the species main nesting beach in Mexico. Thirty years later, the wholesale collection of eggs and slaughter of nesting females has so decimated the species that no more than 250 animals have nested in a single day since 1978 and is down now to less than 117 during their largest nesting.

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*. Every year thousands of endangered and threatened turtles drown in the nets of shrimp fisherman who deploy their nets off our coast in the same waters used by sea turtles. When the turtle finds itself in the way of a net, it usually swims faster but soon it tires and is caught in the net and drowns. 96,000 since 1981 (reported).