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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 21°C (70°F) to 49°C(120°F).
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).