Pearl Oysters
A beneficial pollution indicator or just wanted for its treasure?
Description and Rationale
The pearl oysters are a type of mollusk that is often farmed for their pearls. Pearls are exported from oyster farms in the Philippines and several other Asian countries. They can vary from simple fresh water pearls to the most prized, South Sea pearls for their size, color, and shape. The oysters themselves are farmed then disregarded after harvesting the pearls that are inside the animal.
Is there any use of the oyster itself aside from the economic demand of the pearls? Because it is a filter feeder, can scientists use these oysters to assist them in their research of water pollution levels in the oceans? Has the number of pearl oysters increased, decreased or remained the same? Is the pearl farming industry itself affecting the oceans? If so, are the effects good or bad?
What if there is a way to measure the amount of water pollution in an area? Studies done by the American Physiological Society have released information that oysters, in general, are one of the major filter feeders in the ocean. They stated, “A century ago, the oyster population could completely filter the water in Chesapeake Bay in three days.” They normally live at depths of 8 to 25 ft, which indicates that they live in the costal regions. Because of this, they are one of the first to be exposed and affected by water pollution and rising ocean water temperatures. Although they are farmed in oyster nurseries and their numbers are still abundant, the water conditions could effect and alter the oyster species and other types of ocean life altogether. Is there anything that science can do to prevent this from happening? If there is a way that scientists could use the pearl oyster as an indicator species for investigating the changes in the ocean, it could benefit the ecology of the water-living creatures, land-living creatures and humans.
The main objective of this project is to research both the ecology and biology of the pearl oyster in the Philippines. To use sources such as the Internet and reference books to supplement the studies as well as interview some of the people who are involved with the pearl business. This will help give some observations and understanding of the species and its ability to survive in the ocean.
In this project, I also hope to learn of other ways to measure the water pollution of the Philippines. I would like to look for ways to help improve the health and well being of our bodies of water that provide so much for this country.
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Biology
Common Names and Synonyms
The Pinctada maxima is also called the White-lip oyster. The mollusk itself is not very well known outside of the people who farm them. However, the pearl it produces is quite famous. The South Sea Pearl is a highly valued treasure found in the South China Sea between China, Vietnam and the Philippines. It is commonly farmed by China, the Philippines, and Japan.
Classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia (two-winged)
Order: Pterioida (winged shell)
Family: Pteriidae (winged oyster)
Genus: Pinctada (pearl oyster)
Species: P. maxima (largest)
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Morphology and Physical Description
The Pinctada maxima has a soft, thick, fleshy body and is protected by a hard outer shell. Its size can be very small and grow to be between 13 cm to 30 cm in diameter based on the environment and surroundings it lives in. Scientists determine growth and age based on the weight of the flesh and the shell. However, small differences are seen in the weight of the flesh from one month to another mainly due to changes in the weight of the gonad, or the sexual reproduction organ.
The appearances of the White-lip Oysters are similar to the common mollusk. It has a muscular foot that it uses for movement and lies on the sea bottom. Its shape is irregularly oval and consists of a left and right valve joined together by an elastic ligament that is like a hinge. The muscle that keeps the shell tightly closed is called the adductor. The inside of the valves are white in color. It has two folds of fleshy mantle to coat the oyster's soft body by emitting organic and inorganic substances that make up the shell. Oysters have two pairs of thin lips, or palps, that make up the mouth of the oyster.
White-lip Oysters have a circulatory system, which is comprised of heart, blood and blood vessels. The White-lip Oyster’s respiratory system has siphons or tubes that bring water and oxygen in and releases carbon dioxide. Additionally, oysters have two pairs of gills, which are covered with cilia that help filter the water for the oyster. There are no official nervous systems in an oyster; however, it has ganglia, a mass of nerve tissue, which conducts impulses that serve as its nervous system.
Getting Food
Mollusks in general, are filter feeders. Filter feeders are animals that draw water in their mouths and eat only the small particles and plankton in the water. For oysters cilia lines the gills that draw in water and trap the plankton and small particles in the mucus. Then the radula, a set of small, horny teeth in the mouth cavity, breaks up the food and sends it to the gullet or the esophagus. It goes through the gullet to reach the digestive gland and then on into the intestine. Finally it uses the nephridium (the excretory organ consisting of a tubule with one end opening into the body cavity and the other opening into a pore at the body surface) to get rid of the waste.
Temperature often predicts how much an oyster will eat. Oysters feeding activity is usually at its peak in temperatures above 10°C. At temperatures of 28 °C or higher, the oysters will show signs of exhaustion and feeding slows down. Water temperatures 6 °C or lower will cause the oysters will die.
Since oysters are filter feeders, they assist in filtering out the water they live in. Healthy oysters, at average, can filter up to five liters of water an hour. When it comes to pollutants in the water, oysters can take in the pollutants, make them into small packets and dump them on the ocean floor. If the pollutants don’t affect the oyster it will consume them instead.
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Reproduction
Oyster’s reproduction is unique compared to most animals. An oyster can be either male of female therefore they are protandric. There is no specific gender for each one. Over its life span, an oyster may change from male to female multiple times in order to reproduce. In warmer waters, the sexual maturity age is 1½ years but in colder waters, it would take 4 - 5 years. After they mature, oysters will release sperm into the water as males the first year. Then after 2 or 3 years, they will release eggs into the water as females. Oysters will release millions of eggs or sperm into the water to be fertilized or to fertilize other eggs or sperm. When the egg is fertilized, it will develop into a larva and settle in an appropriate spot where it will develop into an oyster. Ideal water temperatures for them to spawn are higher than 20°C.
Environmental Factors
On average, the White-lip oyster can live to 80 years. Various diseases shortening its life span can affect it by transmission through the water. It is not in any threat of becoming an endangered species and it is also not a threat as an invasive species. Most importantly, the White-lip oyster is a great contributor in filtering out the water in the area where they live. This is what makes them ecologically important. In the Philippines, South Sea Pearl farms can be found in the Northern Provinces along the coastline of the country. Additionally, because South Sea pearls are expensive and highly valued, it is economically important to the people of the Philippines.
Two of the most common diseases that affect oysters are called Dermo (Perkinsus marinus) and Multinucleated Sphere X. Both diseases are caused by a protozoan parasite and are contracted by the consummation of these parasites while the oyster is filtering the water. These diseases are deadly to oysters and can affect the oyster population greatly.
The oyster shell itself is a good habitat for many small algae and particles because of its rigid surface. However, even if the White-lip Oyster has a hard outer shell, the oyster is also prey to other animals. Some of these predators are the starfish and the otter because they have the ability to pry open the oyster’s hard shell and consume the animal inside.
White-lip Oysters are commonly found in sea depths between 8 to 25 feet. Oysters survive best on gravelly grounds. If they are living on sandy or muddy grounds, it will affect its ability to filter the water and may not survive as well.
White-lip Oysters can survive well if the water temperature is suitable. Oysters thrive in temperatures between 20–25 °C because it is a good temperature for both feeding and spawning. If the water temperature decreases to 13 °C oysters will hibernate but if it gets to 6 °C or lower, the oysters will die. On the other hand, if waters are warmer than 28 °C, oysters will show signs of exhaustion from filtering the water.
The Pinctada maximus survives in salt water. It can live in waters with the salinity between 24 – 50%. However if the water salinity is 14% and below or 55% and above, it could kill a large percentage of oysters.
Pearl oysters cannot take high turbidity levels or strong winds and waves in the water. These factors can harm the oysters’ filtration efficiency and affect the quality of pearls they produce. These South Sea Pearl Oysters generally grow in clear water that is undisturbed by strong currents and high silt content.
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Origin and Distribution
White-lip oysters originated and remain in the South China Sea. They are farmed in the lagoons or shallow waters of China, the Philippines and Japan. When harvested, the pearls inside the White-lip oyster are exported to countries around the world where they are sold.
Importance to People
White-lip oysters are farmed and harvested for their pearls. The South Sea pearls are one of the most expensive pearls in this specific economy. This is because of its fairly large size and the almost perfect roundness of the pearl itself.
Pearl farms are located in areas that are protected from strong currents and water pollution. They are usually found in areas away from human population and in places where the water in rich in organic nutrients. When the shells are seeded (supplied with a nucleus so that the oyster will develop a pearl), they are suspended in the water on lines. There the farmers daily check the condition of the oysters. It takes between 20–24 months before they can harvest the pearls.
The shell itself is also used resourcefully. The inside of the shell, which is often called mother-of-pearl, is carved into pieces of jewelry and also used to make decorations. It is also sold in the local market at a reasonable price. These mother-of -pearl products are also exported at much higher prices than the local market pays.
The animal itself is often disregarded when they are done harvesting the oyster. Since it is not edible, there is usually no purpose in keeping the animal itself. Therefore it is either left to decay or it becomes food for other animals. Aside from being food for other animals, there may be a scientific way to use the White-lip oyster animal to investigate the health of the sea.
Since oysters are filter feeders, the body, upon harvesting, can be used in a scientific evaluation of the water’s status. In other words, the oyster body can be used to check the health of the water to measure levels of pollution, acidity or other factors that may be harmful to the marine ecology. Furthermore, because it is a filter feeder, it would most likely be the first to be affected by changes in the water. If we are enabled to know what is happening to the sea, it may help prevent or promote the health of the marine environment and keep or restore the ecology’s balance.
Survivability and Endangered Status
At average, the White-lip oyster can live to 80 years. Various diseases, shortening its life span, can affect it my transmission through the water. It is not in any threat to be an endangered species and it is also not a threat as an invasive species. Most importantly, the White-lip oyster is a great contributor in filtering out the water in the area. This is what makes them ecologically important. In the Philippines, South Sea Pear farms can be found on the islands of Palawan and Mindanao. Additionally, because South Sea Pearls are expensive, and highly valued, the oyster is economically important to the people of the Philippines.
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Potential Solutions
Is the White-lip oyster a potential indicator of water pollution or is it just an animal wanted for its much-valued treasure, its South Sea pearl? At this point, this researcher has not discovered if it is a potential pollution indicator or not. Supplementary research and much needed experiments are needed before determining the oyster’s scientific relevance in the study of the water’s ecological balance. However, there are some other possibilities that might beneficial concerning the use of the animal inside the White-lip oyster. Below are 2 possibilities with an analysis of the advantages and disadvantages for each one.
Possibility 1 A Food Source in the Oyster meat
At the beginning of this project, it stated that eating the Pintcada maxima was toxic and unsafe to eat, but after further research, it was discovered that the meat of the oyster could be eaten. Certain sites specifically distributing oyster meat, sold frozen and preserved Pinctada maxima. Additionally, after having a phone interview with a lady who works with a minority group in Mindanao, Mrs. Sandberg, she stated that the Badjao tribe, after harvesting the White-lip oyster and its pearl, could eat the meat while it is still fresh. She never tried eating the oyster but she stated one of the pastors in that tribe said that it was edible and tastes good. Here is the email she sent me following up the phone interview I had with her:
Hi Nicole,
I could not contact Sahira, so I phoned Pastor Joseph (Badjao).
He told me that the Oyster shell (we called that mother pearl) mussel as long as it is still fresh (oyster meat) it's okay to eat it. In fact, he already ate some of it and he told me it's very delicious and tastes like chicken. Usually, one oyster shell can have 6 to 8 grams of mussel and he told me that one oyster shell can get one to three South Sea pearls depending on how big it is.
After they get the pearl and mussel, the oyster shell can still be valuable because they sell it as a decoration or make it as a ring, pendant, bracelet and earring.
Here's more info:
Pearl cultivation in the Philippines was pioneered by Sukeo and Masayo Fujita in the early 1900s. Their work centered around two main areas: Southern Mindanao, in the Samal Island archipelago, and Northern Palawan's Calamian Island chain in the Sulu Sea and South China Sea.
South Sea Pearl culturing in the Southern Mindanao region of the Philippines took place in the Samal Island archipelago, in the southeast part of the country. White-lipped oysters were transported from the Sulu Sea, on the western side of the Philippines, to be cultivated along the western side of Samal Island. Samal was known for its cultivated gold, pink, and white south-sea pearls.
Pearl cultivation in the Sulu Sea's Northern Palawan region of Southern Tagalog, takes place around Lamud Island, in what is known as the "pearl islands" of Western Busuanga. This is at the northern end of Palawan, between Busuanga island and Culion Island. Pearl cultivation in Zamboanga began in the early 1900s.
The world's largest pearl (Pearl of Lao-Tzu or Pearl of Allah) was found this region in 1934, weighing 14 lbs. There were several unsuccessful attempts to expand cultivation, concluding with the failed "Zamboanga Pearl Farms" in the 1960s. There is still an indigeneous pearling industry in Zamboanga, selling"Badjao Pearls" farmed by the Badjao peoples.
That's all. I hope it help you a lot of this information in your Biology class.
Love,
Cris
Advantages:
1. It gives pearl farmers another food source. This could help feed the farmers’ family by supplying them with another protein source, which is needed for the development of a child’s brain. It could also help cut the costs of buying food since farming the oysters is their source of income and eating the meat would be free.
2. Oysters in many countries are considered a delicacy and can be prepared in many different ways. Many recipes on the Internet have different and unique ways to eat oysters. This may be another, effective way to benefit from the White-lip Oyster in a higher society by selling the meat for a high price.
3. By using the meat as a food source, the whole oyster is used and nothing is wasted. The oyster would be harvested for its pearl, the shell could be used in jewelry, decoration and other useful ways, and the animal would be eaten and not wasted.
Disadvantages:
1. Since oysters are filter feeders they filter out the water and absorb whatever chemicals, minerals, and pollutants are in it. If the White-lip oysters are grown in polluted water or waters that are high in toxic chemicals, then it will contain these variables to a small or a highly concentrated degree. If people eat oysters from these kinds of waters, they can be affected with food poisoning, digestive problems or even death. This is why most oyster farms are located away from large populations of people and in solitary areas where there is not much water pollution. Furthermore, this is why the common people are discouraged from harvesting the oysters themselves.
2. An article on a website stated that how oysters were harvested for food and how they were preserved was crucial to its edibility. If the oysters were self-harvested to be eaten in toxic areas or above water level, there is a high possibility that the oyster can poison the person who eats it. Additionally, if the oyster is intended to be preserved and does not go through proper preservation, the meat can become inedible. Therefore the harvesting and preservation of the oyster needs to go through proper systems that the common people might not have knowledge of.
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Possibility 2 Water Pollution Indicator
As it has been emphasized throughout this report, the oyster species are filter feeders. Therefore, the normal oyster will take in everything in the water both good and bad. If scientists use this as their source for evaluating the water’s health, then there could be an experimental use for the animal. Additionally, if scientists monitor the water’s condition then it would help the earth’s health as well as help us, as humans, to take care of the earth the way God has commanded us.
Advantages:
1. It could be a pollution indicator because it is a filter feeder. The normal oyster can absorb everything from plankton to heavy metals like lead and mercury. It is capable of absorbing the pollutants in the water or discarding it as harmless waste without being harmed too badly itself.
2. There could be another use for the animal instead of just wasting it. It would help scientists and ecologists keep a good monitor of the water and give them early knowledge of any changes and help them become more aware of anything that may harm the animals in the water. By using them for monitoring scientists could keep a check on the ocean’s health.
Disadvantages:
1. There are other systems of checking the water’s ecological balance. Most of them involve the use of chemicals in water sampling, which is a more popular way of checking the water’s chemical balance. Additionally, it may not be necessary to use the oyster if the water sampling is more efficient and modern.
2. Not every oyster that dies will be used to check the water pollution. It might only be necessary to check the water’s status every once in a while. Furthermore, oyster’s don’t die daily or at the needed times when the water may need to be checked. Therefore, if there are no oysters ready to experiment with, then the information scientists need may not be available at the right time.
3. I did not test the hypothesis myself. After asking some of the pearl dealers in a Greenhills Mall, I realized that most of the pearl farms in the island of Luzon, where I’m based, are not South Sea pearl farms and that those types of farms are found near the island of Palawan and in Mindanao. Finally, for the time constraint of this project, the money involved with traveling to another island and finishing up the school year, I personally was not able to test this idea out myself.
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Bibliography
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