Capiz shells and their uses 0809

Capiz Shells and Their Uses



  By: Monica Park



Description and Rationale


Capiz shells are shells that are found in a province in the Philippines called Capiz. A capiz shell, which is found on the coastal waters, is the outer shell of a marine mollusk. The shell is a flat, semi-transparent shell with a pearlescent appearance. The capiz shells are very important to the culture of the capiz people; it is the way that the people in capiz earn money. The shells are not endangered, so there are plenty of Capiz shells in the Philippines, and the government supports the harvesting of these shells.

             What is the capiz shell’s impact on the local ecology of the Philippines? Is it useful for anything else other than jewelry, lamps, ornaments, chandeliers, interiors, walls, or as fashion accents? Will there always be a plentiful amount of the capiz Shells in the Philippines or will these shells be endangered one day? How would the people’s livelihood that depends on these shells for an income change if these shells weren’t there anymore? Is the Philippine government really aware of how many shells are left over?

             Capiz shells are earning worldwide recognition, and are used to make almost anything. What are some of the things that can be made out of capiz shells? In a Philippine internet review about the province Capiz, some of the uses of the capiz shells are for lanterns, lampshades, decorative bowls, curtains, window panels and frames, and eating utensils “(Captivating Capiz Shells).”

             The initial purpose of this project will be to research the biology and ecology of the capiz Shells which is mostly found in Capiz, Philippines through a search of the literature as well as interviews with people working in the capiz shell factory and firsthand observations. These initial findings will help guide the experimental phase, where key variables in the capiz Shells survivability and usefulness will be further explored.

             It is hoped that new uses of capiz Shells will be found that might improve the livelihood of the people living in Capiz and other Filipinos through a more informed understanding of an abundant biological resource.





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Common Names and Synonyms


Capiz Shells are also known as Placuna placenta. This shell is otherwise known as the kapis shell, capiz shell, Hatchet-footed shells, and the windowpane oyster. In the Philippines, the shells are simply known as capiz Shells. The capiz Shell originally got its name because it was harvested near and found in abundance in a small town Capiz which is located in the Philippines.





Kingdom: Animalia

Phylum: Mollusca (Soft)

Class: Bivalvia (two-part shells)

Order: Pterioida (large and medium-sized saltwater clams)

Family: Placunidae (windowpane shells)

Genus: Placuna (windowpane oysters)

Species: Placuna placenta (Window oyster)






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Morphology and Physical Description



External structure

The capiz shells can mature up to 70 to 100 mm in length. The shell is a translucent silvery color and is extremely flattened. Its valves are thin with a V-shaped ligament. The windowpane shells have enlarged gills that help them sift out food particles. The difference of the colors of the shells separates the sex of the shells. The shell of a mollusk is used as a protection for the soft body against the outside world.


Internal Structure

The capiz shells have ventral and dorsal traverse muscle fibers which are present in the axes. The fibers of the ventral set occasionally cross each other.


The capiz has a Mucous gland, which is the mucus-secreting organ of a mollusk, a digestive gland which is the organ of a mollusk that perform the functions of a liver and pancreas, Crop which is a budge of the esophagus of a mollusk, a Stomach which is its digestive cavity, copulatory bursa which is the cavity related to the genital organs of a mollusk, a heart pumps the blood, a pericardium which is the cavity related to the kidneys of a mollusk, situated around the heart, nephridium which performs the functions of kidneys, genital opening which is the opening to the genital organs of a mollusk, excretory pore which is the opening through which a mollusk excretes its bodily wastes, a gill which is the respiratory organ of a mollusk, visceral ganglion; a budge related to some organ in a mollusk, pleural gland which is the tear-secreting organ of a mollusk, pedal gland the organ related to the foot of a mollusk, statocyst which is the organ of a mollusk that provides the sense of body equilibrium, mouth cavity which is the entrance to the digestive tract of a mollusk, a Tentacle which is the organ of touch of a mollusk, an eye which is the sight organ of a mollusk, and the cerebral ganglion which is the brain of a mollusk.


The blood of Placuna placenta is rich in a liquid form of calcium. A soft, outer organ called the mantle concentrates the calcium in areas where it can separate out from the blood, forming calcium carbonate crystals. The mantle deposits sheets of the crystal in varying thicknesses. The individual crystals in each layer vary in shape and orientation. There are three layers to the shell, the first is an outer layer made of conchiolin, an intermediate layer of calcite, and a smooth inner layer composed mainly of calcium carbonate. 

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Getting Food


Capiz Shells are filter feeders. In water, they open up their shells a little. If a current of water is generated through their shells, they sift out the food particles with their enlarged gills. When exposed at low tide, the valves are clamped closed. The Windowpane shells mostly feed on plankton and organic detritus.



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Capiz Shells reproduce sexually by external fertilization. Most aquatic shells lay eggs which are fertilized in the water then hatch into small, free swimming larvae called veliger. The life cycle of the shell is the same as the life cycle as the organism which lives inside of it. When the mollusk dies, its shell is the one part that typically remains intact



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Environmental Factors


Capiz shells can be grown in areas with water temperature 24.5-30oC, salinity 18-38 ppt, pH 6.4-7.7 and dissolved oxygen 2.5-5 ppm. Ideally in transplanted areas density should be limited to approximately 150-200 per m2 (1.5-2.0 million seedlings per hectare) to allow normal growth and prevent overcrowding.



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Origin and Distribution


Capiz shells are originally from the city of Capiz which is in the Philippines. They were first used in the Philippines during the Spanish occupation in making slide windows. The species has a wide distribution including the Gulf of Aden and around India, the Malay Peninsula, and the southern coasts of China.



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Importance to People


Capiz Shells are used for many purposes. Capiz shells can be used as windowpanes, jewelry, ornaments, food, kitchen utensils, and for fashion.


Capiz shells can be used as food. To reduce damage to the shells, they are allowed to dry and open naturally. The meat is then removed and, because of its high protein content, is often used as a component for poultry and shrimp feeds.


There are several ideas about using the Capiz shells as a resource in the Philippines. Capiz shells can be used as food for people and used as a way for people to make a living. The major producing country of capiz shells is the Philippines and exported US$36 million worth of Capiz products between 1986 and 1991. The Filipinos can make even more money using this resource as the demands increase, which creates jobs in the capiz factories in the Philippines.





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Survivability and Endangered Status


Even though the capiz shell used to be easily found in the Philippines, it is starting to become limited. The main cause of the decline in the Philippines and elsewhere is by destructive methods of fishing and gathering such as trawling, using mechanical rakes and dredges, dynamite fishing and compressor diving. Destructive fishing for capiz kills recruits and brood stock and destroys the bottom substrate. It has also been suggested that the increase in prawn hatcheries is also responsible for the decline of capiz. In the late 1980s prawn hatcheries flushed water laced with antibiotics back to the sea and the contamination may have killed capiz. Attempts to slow the decline in this valuable resource include fisheries regulations to control harvesting and aquaculture. In the Philippines, fisheries regulations involve issuing licenses and permits, setting minimum and maximum landing sizes and establishing restricted areas. Regulations are supported by fines and the threat of imprisonment. However, the high market demand means gatherers continue to collect all they can even though the government prohibits the harvest of shells with sizes less than 80 mm and more than 100 mm, and natural resources continue to be depleted. 



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Potential Solutions


How would the people’s livelihood that depends on these shells for an income change if these shells weren’t there anymore? What is the importance of the capiz in the Philippines? It has been established by this point that all the people working in the capiz shell factory have benefited from working at the factory. By working there, they were able to support their families and their needs in life. Without the shells, they would have no job that would help them support their family and their needs. The capiz is useful for many things in the Philippines, if the people of the Philippines continue to pollute the water or do dangerous things that can put the capiz in danger, there will be many problems that will occur to the Filipinos working at the factory or the Filipinos that have jobs that are associated with the capiz. There seem to be several promising possibilities that may help benefit the Filipino industry of capiz. Below are four possibilities with an analysis of the advantages and disadvantages of each.


Possibility 1 - Interview and hand out brochures.


Here in the Philippines, there is a capiz shell factory that employs jobs to many Filipinos. Terence L. Cleak, the owner of one particular capiz factory was willing to be interviewed which would help inform me more about the capiz here in the Philippines and how he runs his business. He was also willing to let me interview ten of his workers in the factory which would help me find out how the capiz industry has been benefiting their lives. Since I researched a lot about the capiz and its benefits to the Philippines, I could use the information I learned and put it into a brochure and hand them out to some people that may be able to help the capiz industry here in the Philippines. By finding more information from people who has had first hand experience, I would be able to inform others about how the capiz industry could also benefit their lives.



1. By interviewing Terence L. Cleak, I would be able to get information from someone who was in the capiz industry for a very long time instead of finding out most of my information online where there is a possibility that some facts are incorrect. I can also find out more about how the capiz industry works around the Philippines from someone who has had a lot of experience.


2. By interviewing the Filipinos at the factory, I could get accurate information on how their lives have benefited by the capiz industry. By getting good information I received from them, I may be able to inform others about the good things about the capiz.


3. By handing out brochures, I could give information people who may not have any idea about the capiz.


4. If the brochures are interesting looking and draws attention, I can interest many people into finding out more information about the capiz.




1. The workers are very important people in the factory with many jobs to finish. By interviewing them, I would be taking some of their work time away from them.


2. Mr. Cleak is a very busy man who has to manage running his own business. I would be taking time from him by asking him for an interview.


3. The people at the factory could also be worried that by giving some information to me, I could reveal some information to rival companies or do something that could give their company a bad name.



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Possibility 2 - Make the shell.


Since there are many capiz shells here in the Philippines, why not use some and try to make something out of it such as a craft?




1. I would know what it would be like to make the shell and how it would feel like to be one of the workers that have to make something out of the shell.


2. I could make my own jewelry when I’m bored and I could save money and have fun by doing this. I could also be making my own designs so I would like the jewelry.




1. After visiting the capiz factory, I realized that it would be very hard for me to make a craft of my own without the materials that I need. It would be hard for me to find my own materials and would cost too much to buy some. I also do not know what materials or tools are needed to make something out of the shell.


2. If I did something wrong while doing the craft, or if I ruined the shell, it would only be a waste of money and resources. If I also realized that I could not make something out of the shell myself, I would have a problem with my possible solutions.





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Possibility 3 - Follow one capiz shell factory worker’s life for a day.

Since I was able to go to interview ten workers, I could ask one of the ten workers if I could follow their life for one day and see how it is like to work at the factory. I would also try to see how the capiz industry influences their lives and I would try to find out how life for them has changed since they worked at the factory.





1. I could see first hand how their life has been benefited by working at the factory.


2. If I were to tell other people about their lives it is more credible and people will be able to relate more from real like experiences other than things found online.




1. Not a lot of people like to be followed around and everyone has their own personal space and might not want me to be there all day.


2. Since the people know that they are being followed, they might change their personality or their lifestyle to make themselves look better and for their reputations sake.






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“Boat Dredges.” Fisheries and Aquaculture Department. 2009. 2 May. 2009 <>.


“Captivating Capiz Shells”. Philippines internet review. 2009. March 23, 2009. <>.


Cleak, Terence L. Personal interview. 2 May. 2009.


“Exploitation of the window-pane shell Placuna placenta in the Philippines.” Science Direct. 2009. 2 May. 2009 <>.


“Fishing with Dynamite in El Salvador.” Deep Sea News. 2009. 2 May. 2009 <>.

“Internal Anatomy of a Mollusk.” The Visual Dictionary. 2009. 29 April. 2009 <>.

“Iron & Capiz Shell Windchime/Lantern, Huge Triple Decker 42” x 12”.” Wild Things. 2009. 2 May. 2009 <>.

“Mini-Review: Fisheries and aquaculture of window-pane shells.” Malacological Society of London. 2 May. 2009 <>.

“Placuna placenta.” The Polistes Corporation. 2 May. 2009. 28 April. 2009 <>.


 “The Biology of Marine Plants.” Google Book Search. 2009. 2 May. 2009 <,M1>.


“The Global Decline of Mollusks.” American Institute of Biological Sciences. 2009. 2 May. 2009 <>.


“The need for conservation and management of Philippine coral reefs.” SpringerLink. 18 January. 1988. 2 May. 2009 <>.

“The Wonders of the Seas.” Oceanic Research Group. 5 June. 2007. 29 April. 2009 <>.

“What is Capiz.” Perlas Oriental. 2007. May 1. 2009 <>.


“What is Capiz?” wiseGEEK. 2009. 2 May. 2009 <>.

“What are Seashells made of?” Ask Yahoo! 2001. 27 April. 2009 <>.



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