The Green
Sea Turtle, Chelonia
mydas, gets its name from the greenish color of
its flesh, not from its shell, which is usually brownish.
It is the largest of the hard shelled sea turtles, and
is characterized by its small head, serrated lower jaw,
and the long tails of the mature males. It is the only
sea turtle species that regularly basks on sandy beaches,
and it may be the fastest swimming sea turtle, with speeds
of 24 km (14 miles) per hour.
The Green Sea Turtle is a large sea turtle with a weight
of 80-220 kg (175 to 485 lbs) and a carapace length of from
80 to 120 cm (30 to 47 in) (Witherington, 2006). Females
have a short tail that reaches just to the edge of the carapace,
while the tails of males are much longer.
The coloring of Green Sea Turtles varies from olive, to
brown, to black (see also Black
Sea Turtle, Chelonia
mydas agassizi, yellow, and creamy-white. They
have beautifully patterned shells, though the markings are
usually not as bold as those of hawksbill sea turtles. The
underside, or plastron, ranges in color from yellow to olive-gray.
Green Sea Turtles have one claw on each front flipper, and
one pair of prefrontal scales. Like the Hawksbill
Sea Turtle, Eretmochelys
imbricata, they have 4 pairs of lateral scutes,
distinguishing them from Loggerhead
Sea Turtles, Caretta
caretta, which have five. The Green Sea Turtle’s
serrated lower jaw is unique among sea turtle species.
Green Sea Turtles are mainly found in tropical and subtropical
waters throughout the world, but they are sometimes seen
in temperate areas as well. Sightings have been recorded
in 140 countries. Important feeding areas are the coasts
of Nicaragua, Brazil, Oman, Vanuatu, Fiji, Japan, Baja California,
and the Pacific coast of South America. Nesting areas are
more strictly confined to 20 degrees north and south of the
equator. Green Sea Turtles are generally migratory, but the
individuals found in Hawaii and the Galapagos spend their
entire life cycles near their place of birth.
While most sea turtles only go ashore to nest, green sea
turtles are known to bask on sandy beaches, both during the
day and at night. This behavior is particularly noticeable
in Hawaii and the Galapagos, and occasionally in Australia
and Mexico. The purpose of this basking is not completely
understood, but it may serve several purposes. It may be
a time of rest for the turtles; it may serve to raise the
body temperature, causing eggs to mature faster as well as
speed up digestion; it may add vitamin D to their systems;
and it may contribute to health of the skin by killing parasites
and fungus.
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| Picture of Endangered
green
sea turtle, Chelonia
mydas, being cleaned by Yellow
Tang, Zebrasoma flavescens,
Gold-ring Surgeonfish, Ctenochaetus
strigosus, and endemic Saddle Wrasse, Thalassoma
duperrey, off Kona Coast, Big Island,
Hawaii, Pacific Ocean. |
Image
#: 020965 |
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Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Testudines
Suborder: Cryptodera
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The diet of Green Sea Turtles varies as they progress from
juvenile to adult. As pelagic phase juveniles, they subsist
mainly on jellyfish and other soft-bodied invertebrates. As
adults, they become vegetarian, subsisting mainly on sea grasses
and algae, which they digest with the aid of bacteria in their
gut. Their serrated lower jaw is useful for cutting off the
blades of sea grasses. Young grasses contain more nutrients,
so turtles keep feeding areas well-mowed, which encourages
the growth of nutritious new grasses.
Like most sea turtles, Green Sea Turtles travel great distances-over
a thousand miles-from feeding grounds to the beaches they
were born. They mate in the water close to where they will
nest. The single claw on each flipper and the flat nail on
the tail of the male are used for grasping the female during
mating. Females lay their eggs at night in clutches of 110-115
golf ball-sized eggs. Eight or nine clutches per breeding
season are laid at intervals of two weeks, and incubation
lasts 55 to 60 days.
Green Sea Turtle hatchlings weigh about 25 g (1 oz.). They
quickly enter the ocean and are rarely seen during their
early pelagic phase. Their size increases rapidly in their
early years when they feed on animal protein, but slows down
later as they age and begin to feed on sea grasses and algae.
Full maturity is reached at the advanced age of from 20 to
50 years.
Unfortunately for the Green Sea Turtle, and in contrast
to the Hawksbill Sea Turtle, its meat is considered particularly
tasty. The oil and fat in the meat has a green hue, which
gave the Green Sea Turtle its name. In some parts of the
world, cartilage from its plastron, called calipee, is scraped
off slaughtered turtles to make the delicacy, green turtle
soup. Green Sea Turtles are even commercially farmed in the
Cayman Islands as food for locals.
Like all sea turtles, Green Sea Turtles face degradation
of habitat, harvest of their eggs, capture in fishing nets,
and death by predators. The IUCN lists the Green Sea Turtle
as Endangered, except for in the Mediterranean region, where
it is Critically Endangered. While their nesting sites are
currently protected in many parts of the world, Green Sea
Turtles are subject to other dangers that may be difficult
to protect against. They are known to suffer from a tumor-like
disease called fibropapillomatosis, which causes wart-like
growths to appear on their skin, particularly around their
eyes. These growths impede eyesight and movement, making
it more difficult for them to survive.
Other common names: Green Seaturtle, Edible Turtle, Soup
Turtle, Greenback Turtle, Tortuga Verde (Spanish) (Witherington,
2006)
For a diagram helpful in identifying the green sea turtle,
see http://marinebio.org/species.asp?id=51
• Green Sea Turtle information assembled from published
and on-line sources by Kevin
Miller on Dec. 31, 2006 for Seapics.com.
Sources:
Perrine,
D. Sea Turtles of the World, Voyageur Press, 2003
Ripple,
J. Sea Turtles, Voyageur Press, 1996
Witherington,
B. Sea Turtles, Voyageur Press, 2006
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