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The diving ability of the sea
turtle is one of its most unique features. Many anatomic adaptations have
been made in the sea turtle in regards to its thermal regulation, respiratory
system, circulatory system, salt secretion as well as its body design that
enable it to dive to extreme depths of the ocean.
Thermal
Regulation
Leatherbacks
are unique from the seven other species of sea turtles. They have often been
called "the champion" of sea turtles due to its amazing capabilities (diving
being one of them). One reason that Leatherbacks can dive to such depths is
due to its ability to withstand such drastic temperatures. The leatherback is
a thermoregulator and thus can tolerate temperatures even as low as six degrees
celsius! The leatherback is also an endotherm while the other seven species
are considered to be ectothermic. The ability to regulate and control its body
temperature is due to certain physiological adaptations that it posesses. First,
the leatherback is the largest of all the sea turtles and with its low surface
area to volume ratio it maintains heat longer than the others. Insulation aids
in maintaining heat as well. The leatherback has an extra layer of blubber (much
like a whale) under its skin which no other known reptile has (Poland 2000).
In addition the leatherback has the quickest metabolic rate when compared to
other reptiles which enables it to use its liver to release heat energy by degenerating
nutrients. According to Davenport (1995) the leatherback also utilizes counter
current heat mechanisms which will be further discussed in the circulatory
system (cited in Poland 2000). The last physiological adaptation is the
large levels of myoglobin and hemoglobin found in Leatherback's blood. These
huge amounts allow them to withstand the temperatures of the deep (Petruzzelli
et al 1996).
Respiratory
System
The respiratory system ingests
oxygen that is necessary for the metabolic processes to be carried out
and also disposes of the harmful product produced when metabolism takes
place, carbon dioxide. Sea turtles have basically the same respiratory
system as all other turtles with the addition of special features for deep
sea diving.
Circulatory
System
The circulatory system of
the sea turtle is vital in its diving ability because the nutrients (i.e.
oxygen) which are vital for metabolic processes are transported throughout
the body by blood through the veins, arteries and capillaries of the circulatory
system. In regards to diving the circulatory and respiratory systems are
closely linked.
Salt
Secretion
Freshwater is not necessary
for the survival of the sea turtle. These amazing creatures can obtain
the essential level of water through their diet and their ability to metabolize
sea water. Similar to other marine animals, sea turtles posses a salt gland
that disposes of excess salt. The salt glands aids the kidneys, which without
the help would be unable to carry out digestion of the extreme amount of
salt taken in by both food and the sea water. The adrenal cortex
of the sea turtle hormonally regulates the glands' function to make sure
the turtle stays hydrated (Prange and Greenwald 1980). This is the metabolization
or conversion of ingested sea water to freshwater that was earlier described.
The salt gland in the sea turtle is found in their eyes. When sea turtles
come ashore often times they appear to be "crying". This is actually the
secretion of excess fluids and most importantly salt from their bodies
(Reina and Cooper 2000).
The body design of a sea turtle
is built especially for swimming and diving. Their forelimbs have been
modified into flippers which act as paddles and facilitate swimming. Also
the neck and limbs can not be pulled into the shell (they are non retractile).
The adaptations of the shell necessary for the extremities to be retractile
would hinder the sea turtles quick swimming ability.
email me: japleasants@davidson.edu
