Clam Anatomy

Clams - The All Purpose Bivalve


Clam Anatomy is shockingly not unlike human anatomy. Clams are sexual animals, and reproduce through spermatozoic means. A clam in its lifecycle may be male, female or hermaphroditic. Males and females release sperm and eggs respectively, and these combine as they free-float (in the wild) to form zygotes. In zygotic form, clams drift while gradually developing a shell.

Their close relation to human anatomy is surprising – one can readily see the evolutionary underpinnings of H. sapiens. The common hardshell clam Mercenaria mercenaria, better known as a cherrystone, has a mouth, labial palps (antecedents of lips), a stomach, separate digestive gland, an intestine, nerve cord and an anus. The foot of a clam is a curved flesh protrusion from the perimeter of the anterior flesh. The foot permits limited locomotion in post-zygotic and adult clams. A ventricle and atrium are present. Clams survive by ingesting microparticles present in seawater through the incurrent siphon, removing the nutritive elements then ejecting the remainder through the rectum to exit the anus. Clams consume phytoplankton, diatoms and other microscopic sea life filtered from the water they ingest, which is also their source of oxygen.

Successful clam procreation is enhanced through industrial means via clam cultivation. This production trend began in the 1960s and 1970s with startups like Cape Cod Cultured Clam, renowned in its area for supporting marine education through free guided tours for children and adults. Many of these firms predate the growing market presence of fish and seafood farming operations, which range from mass hatcheries for freshwater fish like trout that are later stocked in local ponds, to oyster “grants” in bays parceled out by local authorities for caged oyster maturation. The most conspicuous aquaculture initiative in the 21s century has been in-ocean stocking of large populations of popular commercial fish in giant nets, a production innovation brought to the US from Vietnam and other Asian nations. These have been controversial due to the inevitable exchange of pathogens and feed between the netted schools and the larger waters. However shellfish farming, both cultivated (engineered zygoting) and basic (wired cages sunk beneath buoys in the ocean) is generally not considered an active threat to species health.

The industrial production of clams begins with hatcheries, which collect clam seed then carefully cultivate it into larval form. Seed stock, adult clams are induced to release seed by varying water temperature. The fertilized eggs as well as larval clams are then collected, cultivated, and are ready for sale at the size of 1mm. The process is complex and requires heavy capital investment, thus many clam farmers prefer to purchase seed clams produced aquaculturally. At clam nurseries, seed clams are grown in sterilized water tanks until they reach a maximum size of five to six millimeters. The final stage in the process is planting the animals in the ocean inside “bags,” which can be made of anything from iron wire to plastic. Municipalities and states, per state laws lease out clam growth beds to individuals generally on an annual basis.

Worldwide clam population numbers in recent decades have been relatively stable. Besides contamination from local runoff, in particular septic and heavy metal contamination, the main threat to continued, sustainable clam harvesting continues to be seaborne disease. Clams are infected almost annually along the Northeast US coast by dynoflagellates, also known as “red tide.” These normal blooms threaten humans because dynoflagellates express neurotoxins. Other clam diseases do not threaten humans, but can be fatal to the animals themselves.

Share |