Scientific and Technological Issues in Environmental Law

LAW 802

SCIENTIFIC AND TECHNOLOGICAL ISSUES IN ENVIRONMENTAL LAW

PAPER TOPIC:

FIBROPAPILLOMAS AND MARINE TURTLES : AN EXTINCTION THREAT. A CASE STUDY OF GREEN TURTLES.

All species of marine turtles are threatened with extinction. The most serious threats facing marine turtles include the following :

Nesting Threats: Marine turtles throughout the world are in danger as a result of continuing loss of nesting habitat. The loss or reduction of even a single nesting beach can have serious effects.

Increased Human Presence: Increased human presence on beaches, especially at night, including recreational uses discourage nesting activity on beaches that have been used for millennia. This results in nesting females shifting their nesting sites, sometimes being forced to use less suitable beaches, thus aborting or delaying egg laying in the process.

Poaching: The theft of turtle eggs continues to be a serious problem everywhere turtles nest, including within the united States. Turtle eggs are considered to be superior to chicken eggs for use in baking.

Artificial lighting: Artificial lighting from buildings, street lights, and beach front properties has a disorienting effect on turtles, as they abort nesting attempts more often in lighted areas; this has had profound negative effects on nesting behavior and success.

Beach Armoring: Beach armoring includes the building of sea walls, sand bag installations, groins and jetties. Such practices save structures and property from erosion, but ultimately result in environmental damage and loss of a dry nesting beach.

Beach Nourishment: Beach nourishment is the practice of adding sand onto a beach to rebuild what has been lost through erosion. This practice affects turtles by direct burial of nests, or by disturbing nesting activity during the nesting season. Heavy equipment on beaches can pack the sand, making it impossible for turtles to dig proper nests.

Beach Erosion: Human interference has hastened erosion in many places. Even attempts to halt erosion can have negative effects on nesting beaches, as described in beach armoring above.

Predators: Many animals seem to be aware of the nesting cycle of marine turtles, and eagerly gather to ravish nests once the turtles have made them. Raccoons, for example, have been known to destroy as much as 90% of all nests on a beach.

The threat does not end when the egg is hatched. A hatchling must escape the clutches of animals such as foxes and gulls as it tries to reach the water, and even when it reaches the ocean, predators such as sharks await them. Of course the most dangerous predator of all is Homo sapiens.

Commercial Fisheries: In some parts of the world, turtles are still hunted, both for food and for their shells. In places where turtle hunting is banned, the incidental taking of turtles during other fishing operations remains a major threat. For example, shrimp trawlers without turtle excluder devices trap and drown sea turtles. Gill nets also snare turtles, and frequently are not pulled soon enough to free the turtles before they drown. A trapped turtle will struggle, significantly reducing it’s oxygen supply and shortening the time it has before it needs to reach air.

Oil and Gas Exploration: Activities associated with developing offshore oil and gas resources can destroy or seriously disrupt foraging habitat and nesting habitat. Dredging not only destroys habitat, it also results in the incidental injuring or killing of sea turtles. In the same vein, oil spills and the presence of tar in the water have serious effects on marine turtles. Oil on the skin and shell of a marine turtle can affect respiration and salt gland functions, as well as the turtle’s blood chemistry.

Ingestion Of Marine Debris: Drifting garbage thrown into the ocean by humans, collects in the same place as seaweeds do, where hatchling turtles spend their infancy drifting with sargassum and other sea grasses. Young turtles inevitably attempt to eat some of this material, with devastating consequences. Plastic resembles food closely enough to fool even a mature turtle. Ingested plastic is not only toxic, it also obstructs the stomach and prevents the turtle from receiving nutrition from real food. This can often lead to a lingering death.

Fibropapilloma Tumors: Fibropapilloma tumors (FP) are lobe-shaped tumors that can infect all soft portions of a turtle’s body. Tumors grow primarily on the skin, but they can also appear between scales and scutes, in the mouth, on the eyes, and on internal organs. These tumors often increase in size and number until the turtle is seriously debilitated. Death is a common outcome.

Isolated reports of FP in turtles date back as far as the 1930s. For unknown reasons, FP began infecting green turtles in large numbers simultaneously in several geographically discrete areas, such as Australia and Florida. By the mid 1990s the single greatest threat to the green turtle was FP.

A new and alarming development however, is that Fibropapilloma tumors are beginning to show up on other sea turtle species in increasing numbers. If this pattern is not checked, it will not be long before FP outstrips even homo sapiens as the single greatest threat to marine turtles. This paper will focus on this phenomenon known as Green turtle Fibropapilloma tumor. At the same time, if human activities are responsible for, or contributory to GTFP, the question now becomes one of survival, and not of compassion, for if we callously allow ourselves to destroy other species, there is no reason why our destructive behavior will not ultimately eliminate us too.

Green Sea Turtles:

Green sea turtles are reptiles whose ancestors evolved on land and returned to the sea to live about 150 million years ago. They are one of the few species so ancient that they are said to have watched the dinosaurs evolve and become extinct.

The biological classification of the green sea turtle is as follows:

Kingdom: Animalia

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)

Green sea turtles, like all other species of sea turtles, are cold-blooded, they breathe air, their skin has scales, they have evolved a bony outer shell which protects them from predators, as turtles are not known for their speed. The shell covers both the dorsal (back) and ventral (belly) surfaces, and is considered the most highly developed protective armor of any vertebrate species to have ever lived. The dorsal portion of the shell is known as the carapace and is covered with large scale-like structures called scutes. The ventral portion of the shell is known as the plastron. The carapace and plastron are connected at the sides by hard-shelled plates known as lateral bridges. Openings exist between the carapace and plastron for the head, tail, and limbs. While most species of land turtles and tortoises are able to retract their heads into their shells for added protection, sea turtles are not able to do so, and their heads remain out at all times.

Sea turtles have been known to move through the water as fast as 35mph. When active, sea turtles swim to the surface every few minutes in order to breathe. When sleeping or resting, which usually occurs at night, adult sea turtles can remain underwater for more than two hours without breathing. This is due to the fact that turtles are capable of containing higher concentrations of carbon dioxide in their blood than most other air breathing animals, enabling them to use their oxygen very efficiently. Both muscles and blood are able to store oxygen in large quantities, allowing sea turtles to remain underwater for such long periods of time. Juvenile sea turtles have not developed this ability as well as adults and must sleep afloat at the water’s surface.

Green sea turtles, chelonia mydas, get their name from the color of their body fat, which is green from the algae they eat. Adult green sea turtles are herbivores, meaning that they eat only plants, and therefore do not pose a threat to any other marine animals. Similar to cows, green sea turtles depend on bacteria in their guts for digestion of plant material. Juvenile green sea turtles on the other hand are carnivorous. Their diet consists of jellyfish and other invertebrates.

Although the carapaces of green sea turtles are mostly dark brown in color, they can be covered in patches of algae on which fishes in turn feed. This type of feeding arrangement is an example of symbiosis. Symbiosis occurs when a relationship forms between individuals of two different species for an extended period of time. This particular relationship of the fish eating algae off the turtle’s shell would be considered a form of mutualism, a type of symbiosis in which both species benefit from their association. Here, the fish get a free meal, and the sea turtle gets a clean shell.

Although green sea turtles live most of their lives in the ocean, adult females must return to land in order to lay their eggs. Biologists believe that nesting female turtles return to the same beach where they were born. This beach is referred to as a natal beach.

Green sea turtle eggs take about two months to incubate. Studies indicate that the temperature of the eggs during incubation influence the sex of baby sea turtles. Lower temperatures tend to produce males, while higher temperatures tend to produce families.

Because of their efficient mobility in the water and their size, adult green sea turtles have only two known predators: sharks and people. Tiger sharks are believed to feed regularly on green sea turtles. Green sea turtles are found throughout the world’s oceans. Like the other six species of sea turtles, green sea turtle populations are considered either endangered or threatened. While tiger sharks are known to feed upon the green sea turtles, man it seems, may pose a greater threat to the animal’s survival.

What Are Fibropapilloma Tumors?

A papilloma tumor is a benign growth that is spread by a virus. One example is the ordinary wart in humans. Other mammals also develop papilloma tumors.

When papilloma tumors develop predominant fibrous tissue, they are called fibropapillomas. Green sea turtles develop fibropapillomas that appear as lobe-shaped tumors. Tumors grow primarily on the skin, but they can also appear between scales and scutes, in the mouth, on the eyes, and on internal organs.

In the turtles, the early stages of the disease have followed a predictable pattern. First, the turtle developed suspicious white spots on it’s body, most often around the neck and shoulders. Within a year, these white spots usually develop into full blown tumors. The disease frequently affects the eyes first, but this is by no means a rule, as there have been cases of tumored turtles with clean, healthy eyes. Where the tumors begin in the eyes however, they, without exception, appear first in the posterior corner of the eye. If the turtle has tumors in both corners of an eye, the posterior tumor is always larger. Eye tumors often cause drastically reduced vision or blindness.

Most of the turtles observed with the disease steadily worsen. Tumors increase in both number and size. Particularly gruesome are tumors that develop along the neck of turtles.

The principal concern among the public and scientific sectors for this worsening situation centers on the well-being and survival outlook of the green turtle, a protected species under the U.S Endangered Species Act and wildlife laws of the state of Hawaii. Other important concerns include the negative visual impacts related to marine tourism and underwater photography by Hawaii’s substantial skin and scuba diving industry; the perception that toxic pollutants of some unknown nature and origin may be contaminating certain nearshore marine habitats, thereby causing the disease; and possible human health hazards related to exposure to live afflicted turtles and stranded carcasses.

This disease is as tragic as any cancer. For the turtles, tumors, even small ones, mean they become the target of saddleback wrasses and whitespotted tobies. These fish inflict painful bites directly on the fibropapilloma, apparently eating parasites that infest the tumors. Afflicted turtles are often forced to flee from the fish, and over time, their tumors worsen . A thick coat of algae develops on their shells, and even on their skin. Tumors increase in number and size, resulting in more drag, and making swimming more difficult.

Tumors often grow to cover both eyes. Some turtles have been known to have eye tumors so large as to obscure an entire half of one side of their profile. Tumors growing in the corners of the mouth make breathing and eating difficult. Some turtles even have tumors growing out of their anus. No soft part of a turtle is spared.

There comes a point in the disease when it appears the turtle is really just a way for the tumors to get around. There is little turtle left, the way there is little grasshopper left once a spider is finished sucking it dry

Causes:

It is not yet certain what causes fibropapilloma tumors or how they are spread. So far, there are no definitive answers yet as to causation.

Because papilloma tumors are spread by a virus in other animals, it is quite likely that a virus is the culprit in green turtles. There are strong indications that a hypervirus might be the culprit, but available evidence is insufficient to decide the issue.

If a virus is indeed the cause, it is also not yet clear how the virus infects the turtles. Infected turtles have remained in close contact with clean turtles in captivity for years without spreading the disease to them. This seems to suggest a carrier that is present only in the wild, but attempts to identify such a carrier have not been successful so far.

Attempts have also been made to discover whether pollutants could be a factor. But so far, studies have been unable to find any unusual concentrations of pollutants in the afflicted populations.

It is possible though, that the disease is the result of a combination of factors. For example, turtles under stress from pollution could be more vulnerable to a virus that would otherwise be relatively harmless. Again, studies thus far have not been able to find such a relationship.

Study Efforts As To Causation:

(1)Association of herpesvirus with fibropapillomatosis of the green turtle Chelonia mydas and the loggerhead turtle Caretta caretta in Florida:

Source:

“Diseases of Aquatic Organisms; 199, v.37, no.2, p.889—897”

Transmission experiments have implicated a chloroform—sensitive transforming agent present in filtered cell—free tumor homogenates in the etiology of FP. In this study, consensus primer PCR methodology was used to test the association of a chelonian herpesvirus with fibropapillomatosis. Fibropapilloma and skin samples were obtained from 17 green and 2 loggerhead turtles affected with FP stranded along the Florida coastline.

Ninety three cutaneous and visceral tumors from the 19 turtles, and 33 skin samples from 16 of the turtles, were tested. All turtles affected with FP had herpesvirus associated with their tumors as detected by PCR. Ninety-six percent (89/93) of the tumors, but only nine percent (3/33) of the skin samples, from affected turtles contained detectable herpes virus.

The skin samples that contained herpesvirus were all within 2 cm of a fibropapilloma. Also 1 of 11 scar tissue samples from sites where fibropapillomas had been removed, 2 to 51 weeks earlier from green turtles contained detectable herpesvirus. None of 18 normal skin samples from 2 green and 2 loggerhead turtles stranded without FP contained herpesvirus. The data indicated that herpes virus was delectable only within or close to tumors.

To determine if the same Virus infected both turtle species, partial neuclotide sequences of the herpes virus DNA polymerase gene were determined from 6 loggerhead and 2 green turtle samples. The sequences predicted that herpesvirus of loggerhead turtles differed from those of green turtles by only 1 of 60 amino acids in the sequence examined, indicating that a chelonian herpesvirus exhibiting minor intratypic variation was the only herpesvirus present in tumors of both green and loggerhead turtles.

The FP—associated herpesvirus resisted cultivation on chelonian cell lines which support the replication of other chelonian herpesviruses.

These results invariably lead to the conclusion that a chelonian herpesvirus is regularly associated with fibropapillomatosis and is not merely an incidental finding in affected turtles.