Littleneck clam
Mercenaria mercenaria
Description 3
Mercenaria mercenaria has a thick shell, roughly triangular in shape overall, light brown to grey in colour with a violet border and often with varying concentric bands on the shell . These concentric bands are conspicuous and are closely spaced around the margins but more widely spaced around the umbo. The inner shell surface is shiny with a purplish-blue tinge around the muscle scars. The sculpture of the shell consists of thin concentric ridges that are sharp and raised in early growth stages but worn away in older shells. It can grow up to 12 cm in length. The beak extends well beyond the the main shell. The pallial line is short and triangular with a finely rippled inner margin. Each valve has three conspicuous teeth. The internal anatomy is distinctive. The exhalent and inhalent siphons are joined with a fringe of tentacles around the inhalent siphon. The siphons are yellowish or brownish orange at the ends and often streaked with dark brown or opaque white. The foot is large and white in colour.Commonly known as the Quahog and used to make clam juice. This is a non-native species unsuccessfully introduced into British waters several times since the middle of the nineteenth century. The first live specimen was found in 1864 in the Humber. Merceneria mercenaria was successfully introduced from the USA into Southampton Water in 1925. Due to the colouration of the shell, the native American Indians utilised the shell as 'wampun' for use as currency, hence its scientific name.
Food habits 4
Mercenaria mercenaria are suspension feeders which means that they feed on small plants and animals called plankton which are drawn in with water (Britannica 2000, Plourde 2001). When the clam buries itself under a layer of silt and mud it sticks its siphons straight up through the surrounding muck. The inhalant siphon draws in water, which is passed over the gills. Millions of tiny cilia, hair-like structures, move the water across the gills and any food particles are caught in a mucous sheet that coats the gills (Plourde 2001, Stewart 1996). This food-mucous mixture is passed along a groove above the foot to a pair of muscles called the palps, which force the material into the mouth (Plourde 2001). It then follows the digestive tract consisting of a stomach, intestine, and anus to be excreted through the exhalent or excurrent siphons, as pseudofeces (Britannica 2000, Plourde 2001).
Habitat 5
Mercenaria mercenaria are found most abundantly on mud flats, mud/sand flats, and sand flats which reach depths of 10 m (Plourde 2001, Stewart 1996). However, soft muddy bottoms cannot support the weight of the clam due to its heavy shell. This causes sediments to be stirred up, and silt may block the siphon of the clam from filtering out the water (Stewart 1996). Also, it is important that they have tides in order to receive food and oxygen and to carry away waste, but turbulent waters, found in the surf zone, may wash them away (Stewart 1996). The perfect salinity range for Mercenaria mercenaria larvae are 20 to 35 parts per thousand, however adults can be more tolerant (Stewart 1996). The Chesapeake bay is an excellent habitat because it provides the needed salinity and temperatures that are optimal for the hard-clam's survival.
Aquatic Biomes: coastal
Sources and Credits
- (c) Casey Dunn, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/12455333@N00/6195860344
- Wikimedia Commons, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/LittleNeck_clams_USDA96c1862.jpg/460px-LittleNeck_clams_USDA96c1862.jpg
- (c) The Marine Biological Association of the United Kingdom, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/10658115
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18657993
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18657990
