Pinctada maxima (Jameson, 1901) - gold-lipped pearl oyster shell. (public display, Field Museum of Natural History, Chicago, Illinois, USA) Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates. Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood. The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record. Shown above is the interior of a gold-lipped pearl oyster shell. The rainbow-colored iridescence of the shell is nacreous aragonite (CaCO3 - calcium carbonate), also called "mother-of-pearl". This species makes white pearls. Pearls are spherical to subspherical to irregularly-shaped, biogenic concretions of slightly iridescent, nacreous aragonite. Pearls are principally made by pearl oysters. Natural pearls are scarce. Well-formed, spherical natural pearls are rare. Fossil pearls are known, but are also scarce. Mother-of-pearl is relatively common. Well-known pearl oysters include Pinctada margaritifera (the black-lipped pearl oyster), Pinctada fucata (Japanese pearl oyster), and Pinctada maxima. Mother-of-pearl is well developed in shells of other species such as Pinctada imbricata (Atlantic pearl oyster), Pteria colymbus, Pteria penguin (both are winged pearl oysters), Haliotis spp. (abalones), and Atrina spp. (pen shells). Natural pearls form when foreign objects, such as sediment grains or other debris, enter a pearl oyster and get embedded in its mantle tissue. The particle is slowly coated with nacreous aragonite, which prevents the particle from causing disease or injury. The end result is a biogenic concretion called a pearl. Natural pearls show a concentric structure through the entire cross-section. Almost all commercially available pearls are semi-natural - they have been cultured. Cultured pearls have been available for many decades. A spherical bead is placed inside a pearl oyster, under its mantle tissue. The bead is slowly coated with nacreous aragonite to produce a cultured pearl, which shows concentric structure only in the outer portions of its cross-section. Marine pearls can be whitish, pinkish, yellowish, or blackish. Freshwater pearls are also known - natural examples vary from ~spherical to highly irregularly-shaped. Blister pearls are attached to the host mollusc's shell. Classification: Animalia, Mollusca, Bivalvia, Pteriomorphia, Pterioida, Pteriidae See info. at: en.wikipedia.org/wiki/Pinctada_maxima
Summary[
edit] Description: Magyar: Feltálalt éti osztriga vagy európai lapos osztriga (Ostrea edulis) az angliai Whitstable-ban. English: European flat oyster, mud oyster or edible oyster (Ostrea edulis) as food in Whitstable, England. Date: 28 May 2016, 14:06:31. Source: kindly granted by the author. Author: Emőke Dénes. Permission(
Reusing this file): This file was created by Emőke Dénes and uploaded by
DenesFeri. : This file is licensed under the
Creative Commons Attribution-Share Alike 4.0 International license. :. You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the
same or compatible license as the original. https://creativecommons.org/licenses/by-sa/4.0 CC BY-SA 4.0 Creative Commons Attribution-Share Alike 4.0 truetrue. : This work is
free and may be used by anyone for any purpose. If you wish to
use this content, you do not need to request permission as long as you follow any licensing requirements mentioned on this page. Wikimedia Foundation has received an e-mail confirming that the copyright holder has approved publication under the terms mentioned on this page. This correspondence has been reviewed by an
OTRS member and stored in our
permission archive. The correspondence is available to trusted volunteers as
ticket #2017083110036563. If you have questions about the archived correspondence, please use the
OTRS noticeboard. Ticket link:
https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom&TicketNumber=2017083110036563..