Donax variabilis (variable coquina clam) & trail & burrow (Cayo Costa Island, Florida, USA) 4 : 無料・フリー素材/写真
Donax variabilis (variable coquina clam) & trail & burrow (Cayo Costa Island, Florida, USA) 4 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Donax varaibilis Say, 1822 - variable coquina clam in Florida, USA. (December 2012)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 a variable coquina clam, Donax variabilis. It has a smooth, small, Tellina-like shell that varies considerably in color (hence the species name). It is common in shallow marine sandy environments, ranging from the intertidal zone to moderately shallow subtidal settings. This light-colored specimen is recently-deceased with its shells still articulated. It is in a supratidal part of a sandy marine shoreline. It likely reached this area during a then-recent storm, which usually results in a temporarily high sea level (storm surge). After the storm, the clam found itself in a non-permanently wet or moist environment and emerged from its burrow before dying.Variable coquina clams can be abundant in intertidal zone sandy beach environments of southwestern Florida. When the sand is disturbed (pick up a couple handfuls in the swash zone and place it back down), many Donax are often visible - they immediately burrow back down into the sediments.Classification: Animalia, Mollusca, Bivalvia, Heterodonta, Veneroida, DonacidaeLocality: supratidal zone of marine beach near the southern end of the western shoreline of Cayo Costa Island, Gulf of Mexico coast of southwestern Florida, USA (vicinity of 26° 36' 51.30" North latitude, 82° 13' 24.39" West longitude)------------------------More info. at:en.wikipedia.org/wiki/Donax_variabilis |
| 撮影日 | 2012-12-17 15:47:39 |
| 撮影者 | James St. John |
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