Capiz shell

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Capiz shell
Systematics
Subclass : Pteriomorphia
Order : Pectinida
Superfamily : Anomioidea
Family : Placunidae
Genre : Placuna
Type : Capiz shell
Scientific name
Placuna placenta
Linnaeus , 1758

The windowpane oyster ( Placuna placenta ) is a in the Indian Ocean from the Gulf of Aden to India and China Sea common mussel . It is of particular economic importance because of its translucent shell. It bears its name after the province of Capiz ( Filipino : Kapis ) on the island of Panay , which belongs to the island state of the Philippines .

features

The strongly flattened, almost round housing with an irregularly shaped edge and a short, straight lock edge has a diameter of 5 to max. 18 cm, usually by 10 cm. The dorsal edge can sometimes protrude slightly forwards and backwards. The left housing flap of the Capiz shell is flat to slightly convex , the right housing flap is slightly concave . The mussel shell is up to 1 mm thick; it is more or less translucent and dull white. It consists of calcium carbonate in a matrix of organic material. The calcium carbonate is in the mineral modification calcite . The outside of the case is almost smooth, it only shows numerous, very fine, radial lirae. The mostly also very fine concentric growth strips can form fine to strong, roof-tile-like wrinkles. The external ligament forms a tight ligament on either side of the vertebra. The internal ligament forms a V-shaped structure, with the posterior branch being significantly longer than the anterior branch. A pallial line is missing. There is practically only one central, approximately round sphincter muscle, as well as a very small anterior foot retractor muscle that attaches to the branches of the internal ligament. The rear left foot retractor muscle sits within the large sphincter muscle. The clogged , very small, former byssus hole can be seen below the upper edge on the right flap . The inside of the case is smooth and shiny, mother-of-pearl , with faint, radial lines. Only the front and back inner edge is often roughened.

Geographical distribution and habitat

The Capiz mussel is common in the Indian Ocean from the Gulf of Aden to India and in the China Sea . It can also be found in the tropical warm coastal waters of the Philippine archipelago, especially in the eponymous province of Capiz . It is usually found there at a depth of about 3 to 20 m, rarely up to 100 m.

Way of life

The Capiz mussel is separate from the sexes. Sperm and eggs are released into the open water, where fertilization takes place. The eggs measure 56 ± 5 µm in diameter. According to observations in the laboratory, the embryonic phase is only about 6 hours (at 27 ° and 33 per thousand salt content). The first crawling Pediveliger appeared on the 9th day, the metamorphosis was completed after 14 days. A byssus and a byssus hole are formed only very shortly after the larval phase; the byssus hole is quickly overgrown. Most of the life there is neither a byssus nor a byssus hole and the animal does not live grown on the sediment surface. It lies flat on the mud on the right or left flap, not attached; without preference for one or the other key.

Systematics

The genus Placuna was transferred in 1977 together with the genus Placunanomia from the family Anomiidae to the family Placunidae. Placunanomia differs from the Capiz mussel and the other species of the genus Placuna by the byssal apparatus , with which it remains connected to the substrate throughout its life, while Placuna only leads a sessile way of life for a short period after the larval stage. Therefore, based on current knowledge, the Placunidae family only includes the species of the genus Placuna with the Capiz mussel as a type. It has a different lock formation from the Anomiidae, which includes a secondary lock strap.

Economical meaning

Christmas decorations made from capiz shell

In the 16th century, the translucent shells of the Capiz mussels were used by the Spanish colonizers for the production of window panes, which earned the Capiz mussels the nickname "window pane shells". Today the Capiz plates are used to decorate room dividers, paneling, lampshades, trays, wind chimes and Christmas decorations. The processing of the Capiz bowls is complex: First the transparent inside is separated from the outer shell, carefully cleaned and polished. It is then soaked in a peroxide solution and made malleable, then smoothed, cut and cured in an oven at 200 ° C. Finally, the Capiz pane is primed and colored as required and given a food-safe synthetic resin coating.

The Capiz mussel can form small pearls that are used in the pharmaceutical industry.

Danger

The high demand for Capiz mussels has led to a significant overexploitation of the mussel colonies in the past decades , so that the natural stocks have declined sharply. Protective measures in the Philippines in the form of usage restrictions through the controlled issuing of state harvest licenses, the creation of protection zones and the establishment of minimum harvest sizes have so far been unsuccessful. Today, an attempt is therefore also made to support the population through breeding in aquacultures .

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Individual evidence

  1. ^ Antonio G. Checa: Crystallographic structure of the foliated calcite of bivalves. Journal of Structural Biology, 157 (2): 393-402, 2007 doi: 10.1016 / j.jsb.2006.09.005
  2. ↑ Biosearch, Bioinformatics Center, National Institute of Oceanography, Goa, India: Placuna placenta (Linnaeus, 1758) (Oyster). 2009. ( Online )
  3. ↑ a b BS Ingole, S. Clernente: Status of Windowpane oyster Placuna placenta (Linnaeus) population in Goa. Society for Marine Archeology 2006 ( Online ; PDF; 393 kB)
  4. ^ OBIS Indo-Pacific Mollusk database: Placuna (Placuna) placenta (Linnaeus, 1758). ( Online )
  5. ↑ Jocelyn A. Madrones-Ladja: Notes on the induced spawning, embryonic and larval development of the window-pane shell, Placuna placenta (Linnaeus, 1758), in the laboratory. Aquaculture. 157: 137-146, 1997 doi: 10.1016 / S0044-8486 (97) 00151-8
  6. ^ S. Dharmaraj, K. Shanmugasundaram, CP Suja: Larval rearing and spat production of the windowpane shell Placuna placenta. In: Aquaculture Asia April-June 2004 (Vol.IX No. 2) ( Online ; PDF; 406 kB)
  7. ↑ a b Yonge (1977: p. 502ff)
  8. ↑ Claire Campbell: Fisheries and aquaculture of window-pane shells. Bulletin of the Malacological Society of London. ( Online, accessed on December 4, 2010 ( Memento of the original from July 21, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. ) @1@ 2Template: Webachiv / IABot / www.malacsoc.org.uk

literature

  • CM Yonge: Form and evolution in the Anomiacea (Mollusca: Bivalvia) - Pododesmus, Anomia, Patro, Enigmonia (Anomiidae); Placunanomia, Placuna (Placunidae, Fam. Nov.). Philosophical Transactions of the Royal Society of London B, 276: 453-527, 1977. doi: 10.1098 / rstb.1977.0005

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