Green Sea Turtles and Structural Traits - Essay Example

Green Sea Turtles Green sea turtles are a group of shelled reptiles that live in the ocean. This paper tends to discuss them in general. First of all, an introduction to green sea turtles has been given along with their biological classification. Their structural traits have been discussed in detail with emphasis on their shells, limbs, breathing and metabolic system. After that, their habitat has been described followed by a discussion about diet. The next section takes into account their reproduction and mating. Their lifespan has been discussed. Last section is regarding their predators and threats. The report is summarized in a concluding paragraph and APA referencing style has been used properly both for in-text citation and referencing. Introduction Green sea turtles, or honu (pronounced hoe-new), are those reptiles whose ancestors, around 150 million years ago, were known to have evolved on land and then moved to sea. These turtles are one of the oldest species which has seen the evolution and extinction of dinosaurs. It is important to describe here the biological classification of green sea turtles. Kingdom Anamalia Phylum Chordata (vertebrates) Class Reptilia (reptiles) Order Chelonia (turtles and tortoises) Family Cheloniidae (true sea turtles) Genus Chelonia Species mydas sub-species aggazizi (Hawaiian population) Structural Traits Green sea turtles possess all the traits of reptiles and the other species of sea turtles. They are cold blooded animals, meaning that they change their body temperature according to the environment or, in other words, take body heat from the environment. They breathe air and have scales on their bodies like many other reptiles. They have got their name because of the color of their body fat which is green. This green color is because of the algae or limu that they eat. An adult green sea turtle weighs over 500 pounds. Like all other turtle species, green sea turtles possess a hard and bony outer structure called shell whose function is to provide protection to the turtle from predators. This hard shell covers both the dorsal and the ventral part of the turtle’s body and is known to be the hardest and an exceedingly developed weapon that any vertebrate can ever possess. The part of the shell that is on the dorsal (back) side is known as the carapace. This portion is heart shaped and is as long as 5 feet. It is covered with large scales which are called scutes. The ventral part of the shell that covers the belly is known as the plastron. The dorsal and ventral parts are connected to each other at sides through hard-shelled plates which are known as lateral bridges. The connection between the carapace and plastron breaks at openings for head, tail and limbs. The difference between green sea turtles and land turtles and tortoises is that green sea turtles are not able to retract their small heads into the shell for extra protection. The shells of green sea turtles are very light weight and are more developed as compared to shells of land turtles. The limbs seem like flippers that help them swim long distances in less time efficiently, making them refined swimmers. Apart from protecting themselves with the help of shells and swimming by means of flippers like limbs, green sea turtles are also able to get rid of salts which accumulate in their bodies due to their living in sea waters. To serve this purpose, there is a little salt gland behind each eye. The salt glands help in maintaining a balance of healthy water by shedding the excess salt in the form of tears. Therefore, we should not get alert when we see a green sea turtle crying because they do not shed tears as they are unhappy, but because it is their natural way of keeping their body system in check. Moreover, male and female green sea turtles look very similar until they reach sexual maturity. After maturity, we can tell which is male and which is female. The tails of mail turtles are long and think while those of females are short and stumpy. This is sexual dimorphism in which we are able to tell the difference between male and female species by looking at their outer body features. Habitat There are four existing species of sea turtles out of seven that can be found in Hawaiian waters. These species are: the green sea turtle, the hawksbill, the leatherback and the olive ridley. The green sea turtle is by far the most common of all these species. As the name implies, the bodies of the green sea turtles are beautifully adapted for life in ocean. They are most commonly found living near coral reefs and rocky shorelines where algae and limu is in large quantity. The speed of green sea turtles with which they swim across the water is around 35 mph (Fletcher & Scherer, 2006, p.6). When they are active, they are able to swim to the surface of the water to breathe in air every now and then. They are not active when they are resting or sleeping which is the state in which they remain under the water without breathing for two hours at maximum. This is the case with adult turtles. Younger ones need breathing more often. The reason why turtles are able to stay underwater without breathing is that their bodies are able to contain higher concentrations of oxygen in their blood and muscles which enables them to use oxygen more efficiently. The bodies of young turtles are not able to store oxygen this efficiently so they have to come at the surface more often or they have to sleep floating at the waters surface. Diet As described earlier, the green color of the honu is because of the algae they eat. Adult turtles are herbivorous in nature which means that they feed on plants only. This characteristic makes them harmless to other animals living under water with them like fish. One characteristic of them which is similar to cows is that they hold bacteria in their guts and depend on them for digestion of plant food. This is the case with adult turtles only. Young turtles are carnivorous. They feed on jellyfish and other little invertebrates. The dorsal surface of the shell or the carapace is dark brown in color but it gets covered with patches of algae on which fish feeds. This kind of feeding arrangement is an example of symbiosis which is a process of relationship formation between two different species for long time period due to some reason. The relationship between fish and green sea turtles is called mutualism which is a kind of symbiosis. In this type of relation, both the species get benefit from each other. Fish gets its diet from the turtles’ shells, and the turtles’ shells get cleaner in return. Reproduction Despite the fact that green sea turtles live in oceans, adult female turtles have to return to the land to lay their eggs. Research suggests that nesting females lay eggs on the same beach on which they were born. It is wonderful how they find their natal beaches. This beach is called the natal beach to reach which the nesting females have to cover long distances which may be as long as 800 miles (Smith, Dauncey & Goodall, 2007, p.127) from feeding grounds for the Hawaiian green sea turtles. They can move along the coasts of the Hawaiian island to their natal beaches that may be located 800 miles far away in the Northwestern Hawaiian Islands. Male turtles accompany their female counterparts when they are migrating to the natal beaches in late springs. Mating occurs at the shores of the natal beaches. Mating does not occur every year but the year in which it occurs, females have to come ashore much often at nights to makes nests and lay eggs. French Frigate Shoals are the most popular natal beaches where most of the Hawaiian green sea turtles mate and females lay their eggs. Females come ashore at the dry sand of the beach with the help of her front flippers. It is difficult for her because the flippers are adapted to swimming more than supporting the turtle in sand. When she reaches the sand, she uses all her flippers to dig out a nest and burrow where she lays 100 eggs, called the clutch, and covers them with sand after which she returns to the sea. Eggs incubate in two months. Research suggests that lower temperature inside the eggs results in male sex while higher temperature results in female. Baby turtles hatch out of eggs by chipping at the shells with the help of their egg teeth which are temporary hard structures found at their beaks. The group of baby turtles takes several days to dig their way out of the nest. They stop digging when they feel that the sand is hot which indicates that it is day time and they may face predators and harsh sunlight. So, they resume digging in the night when the sand is cold. When they come out, they swim to the ocean. Many of them lose their way and are eaten up by crabs, sharks and other predators. Those who survive are very few in number and they stay near the surface until they go inshore after around a year. Lifespan The exact lifespan of green sea turtles is still unknown. Hawaiian sea turtles grow very slowly. The growth is so slow that they take 10 to 50 years to be able to become sexually mature to reproduce (Bredeson, 2007). The average age of maturity is 25 years. Due to this long lifespan and period of maturity, green sea turtles take too many years to recover from a significant population decline. Predators and Threats to Survival There are only two predators for adult green sea turtles. These are either sharks or human beings. Green sea turtles are a regular food for tiger sharks which are found in larger numbers near the natal beaches located at Northwestern Hawaiian Islands. To escape from tiger sharks, these turtles move to the beaches and stay there for hours under the sunlight, lying still. Doing so is called basking which not only saves them from sharks but also provides them body heat which they need to regulate their metabolism. Hunting of green sea turtles is also common. Men use their shells to make ornaments and jewelry. Their skin is used in the preparation of many leather goods. Also, men eat their meat and eggs, and make turtle soup. The fat obtained from their meat is used to prepare oil. They have been used to feed crews fishing crews in the Northwestern Hawaiian Islands. They are also caught accidently in fish catching gear and driftnets thrown in oceans by commercial shrimp fishers. There are devices like turtle excluder devices (TEDS) which law demands fishermen to use while catching fish. Still, very few fishermen use such devices. Other threats include the litter like plastic bags and marine debris that accumulates in the oceans. This proves lethal when turtles swallow the debri or get entangled. When turtles swallow plastic material, they are not able to digest it due to which it remains inside the stomach for longer periods releasing toxicity and clogging the digestive system. Oil and tar gets stuck in their throats and stomachs causing them to die. Noise and disturbance at nesting beaches which occurs due to developmental tasks is also deadly for the young turtles. The disease fibropapilloma has recently destroyed many green sea turtles living in Hawaiian Islands and Florida. This disease caused the development of deadly tumors on inside the tissues of turtles’ bodies. What caused this disease is not known; however, scientists blame marine debris and water pollution to be the trigger of this disease. Due to increased hunting and commercial trade, the species is threatened or endangered according to the Federal Endangered Species Act of 1973. The green sea turtles living off the coast of Florida and the Pacific coast of Mexico have already been announced as threatened. This threat has greatly reduced their number from several million to around two million because of the fact that the surviving turtles take too many years to reach sexual maturity. Conclusion The paper discussed in detail the general information about green sea turtles. They are one of the oldest species of vertebrates and belong to class Reptilia. They are cold-blooded. They possess an outer body shell that protects them from predators. The small head is non-retractable. The limbs act like flippers helping them to swim across the ocean. They store oxygen inside blood and muscles due to which they can remain underwater for extended periods. Juvenile turtles come at the surface for breathing more often. They live where algae and limu is plentiful. They share a symbiotic relationship with fish. Young turtles are carnivorous. Adult turtles come offshore to mate and female turtles lay eggs at their natal beaches. Babies hatch out and dig their way to the sand and then move to ocean. Most of them are eaten up by predators on their way. Tiger sharks eat green sea turtles in large quantities to escape whom the latter come offshore in day time to rest under the sun. Human beings hunt them and use them in preparation of food, jewelry, leather goods, and ornaments. Turtles also ingest marine debri and litter which causes death. They may also get entangled with fish catching gear, ingest plastic, or catch diseases which are all deadly for their survival. The Federal Endangered Species Act of 1973 has listed them as threatened species and has passed laws which have increased their chances of survival to some extent. References Bredeson, C. (2007). Fun Facts about Turtles. USA: Enslow Publishers, Inc. Fletcher, M., & Scherer, G. (2006). The Green Sea Turtle: Help Save this Endangered Species. USA: Enslow Publishers, Inc. Smith, E., Dauncey, G., & Goodall, J. (2007). Building an Ark: 101 Solutions to Animal Suffering. USA: New Society Publishers. Read More