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Historically, wild populations of the Asiatic clam were exploited and harvested, to the extent that , locally, the clams once faced endangerment or extinction. Today, the clam thrives throughout the world.
IUCN Red List of Threatened Species: no special status
The clam creates a problem for power plants by blocking the ventalation systems and the water intake valves. Combined costs of outages, reductions in efficiency, capital investment in equipment, labor and chemical control, exceed 1 billion annually.
The Asiatic clam is a major source of food and is harvested by humans throughout the world. The clam, when removed from its shell, also makes good fishbait.
The Asiatic clam is a filter-feeding bivalve. It filters microscopic organisms, such as plankton, from the water.
The Asiatic clam is found throughout Asia, North and South America, Europe and parts of Africa. The clam occurs primarily in streams south of 40 degrees latitude in the northern hemisphere.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); neotropical (Native )
The Asiatic clam prefers a lake or stream that has a a sandy or gravel substrate. However, they are also located underneath large boulders and in soft silts of deepwater lakes. The clam thrives better in fast flowing waters because the currents supply a constant source of the particulate food that the clam consumes.
Aquatic Biomes: lakes and ponds; rivers and streams
Other Physical Features: ectothermic ; bilateral symmetry
The Asiatic clam is hermaphroditic, with single genopores on each sides of the body. Reproduction and larval release occurs biannually in the spring and in the late summer. The clam is believed to practice self-fertilization, enabling rapid colony regeneration when colony populations are low.
Vernacular names.
Corbicula fluminea is a species of freshwater clam native to eastern Asia which has become a successful invasive species throughout North America, South America, and Europe.[1] Corbicula fluminea is commonly known in the west as the Asian clam or Asiatic clam. In Southeast Asia, C. fluminea is known as the golden clam, prosperity clam, pygmy clam, or good luck clam.
Corbicula have had global success as an aquatic invasive species, having been introduced to a novel range including South America,[2] North America and Europe. Human industrial activity, such as transport of larvae via ballast water in container ships, has been noted in the literature as a chief invasion vector.[3] A market exists for Asian clams for human consumption in Japan, China, and other countries in the region.[3] According to the United States Geological Survey, C. fluminea is likely to continue to expand its North American range until it reaches the maximum extent of its low temperature tolerance.[4] The periostracum of the shell is normally yellow-green, with concentric growth rings of the prismatic layer visible through the proteinous outer layer. The periostracum can flake, allowing the white prismatic layer to show through. The shells exhibit a light purple nacre on the inside.
Right after reaching maturity, these clams produce eggs, followed by sperm. Throughout adult life, Corbicula is a self-fertile simultaneous hermaphrodite which can broadcast spawn up to 570 mucoid larvae per day per individual, and more than 68,000 per year per individual.[5] Larvae are ~200 microns in length when discharged from an adult and dispersed through water until becoming sessile adults.[5] Adults can reach a length of about 5 centimetres (2.0 in).
Corbicula fluminea is an active suspension feeder, and in the process of feeding by pumping water through its body (as well as feeding on interstitial sedimentary material via pedal feeding when suspended grazing items are limited).[6] They feed primarily on phytoplankton (algae), which they actively filter out the water, but may pedal feed on organic matter in the sandy or muddy bottoms of streams, lakes, or canals where the clam establishes a population.[1]
Corbicula fluminea is a species of freshwater clam, an aquatic bivalve mollusk in the family Cyrenidae.[7] C. fluminea is often confused with Corbicula fluminalis due to the two species' similar color and texture. Two species may be present in some introduced populations: C. fluminea and C. fluminalis.[8] The names themselves are similar in the literature (e.g. by being called "Corbicula fluminata").
The ratio of width and height in C. fluminea is on average 1.1. In C. fluminalis it is smaller (0.97); still, there is much variation and considerable overlap in shape. Most easily, they can be distinguished by the number of ribs on the shell; C. fluminea has 7 to 14 ribs per cm, C. fluminalis 13 to 28.[9] This character is already clearly recognizable (albeit only by direct comparison) in very small (5 mm diameter) specimens. In addition, when viewed from the ventral side (looking at the opening between the shells), C. fluminalis is rounder, almost heart-shaped, while C. fluminea has a slightly flatter shape like a teardrop with a notched broad end. Small specimens of C. fluminalis are almost spherical, while those of C. fluminea are decidedly flattened. All these differences except the rib number are a consequence of C. fluminalis having a markedly more swollen, pointed and protruding umbo.
This clam originally occurs in freshwater environments of Eastern Asia, including Russia, Thailand, the Philippines, China, Taiwan, Korea, and Japan. C. fluminea also occurs naturally in freshwater environments of Africa.[10]
Many coastal rivers with a heavy industrial shipping presence in the invaded range of C. fluminea sustain Asian clam populations.[3] Various non-indigenous populations of C. fluminea include:
Human activities are the chief reason for the wide dispersal of C. fluminea as an invasive aquatic organism.[3] Its global invasion probably started with Asian immigration in North America during the 1920s, as it was used as food source by these communities.[3] Corbicula fluminea, along with other exotic bivalve larvae, may be accidentally transported via ballast water or recreational boaters.[3] Furthermore, the species is common in the aquarium trade and can be intentionally or unintentionally released in the wild by aquarists.[3]
Corbicula fluminea enjoys several physiological capabilities which are advantageous in promoting its invasion of novel lentic/lotic environments including:
Corbicula fluminea is a self-fertilizing, simultaneous hermaphrodite which can asexually produce internally-brooded, semi-buoyant planktonic larvae when spermiogenesis is induced at temperatures above 10 °C.[5] This allows C. fluminea to colonize novel habitats at an advanced rate.[37]
Studies on which abiotic habitat characteristics are most strongly associated with Asian clam population abundance have produced varying results. Brazilian habitats have been found to have support the largest abundances of invasive Corbicula spp. in areas with coarser dominant sediment fractions, while negatively correlated with increasing levels of organic matter.[38] Others studies have shown abiotic habitat characteristics such as water redox potential, inorganic nutrient content, hardness, and organic matter content in tandem with the amount of very coarse sand combine to explain 59.3% of Corbicula population habitat association via statistical tests.[30] Asian clam invasions seem to be limited by elevation (88% of the invaded range is below 500m elevation[1]), latitude (90% lies between latitudes 30°and 55°[1]) as well as the minimum winter temperature (-10 °C) of the ecosystem.[1]
Corbicula fluminea reworks the sediments it resides on through the process of bioturbation.[6] Asian clams are considered biodiffusors similar to marine clam species due to their observed bioturbation activity which may negatively affect biogeochemical affect other members of the benthic community in invaded areas.[6]
Corbicula has also been shown to profoundly influence community dynamics within the macrobenthos of invaded systems.[39] Corbicula has been shown to remove as much as 70% of phytoplankton biomass in reaches of invaded rivers with a robust clam population.[40] The clam has also been reported as causing a decline of dissolved oxygen in the water of the same river system with wide ranging second-order effects.[40]
The primary economic and social impact of the invasion of C. fluminea has been billions of dollars in costs associated with clogged plumbing and, heat exchangers, or other human-created infrastructure.[41] Ecologically, C. fluminea contributes to declines and replacement of highly vulnerable, already threatened native clams.[42]
The first recorded instance of Corbicula presence in the scientific literature in the Western Hemisphere was of its introduction into British Columbia circa 1924, followed by a spread throughout the Pacific Northwest and across the American south through South America. Invasions in Europe and Central America were more recent, first appearing in Caribbean countries in 1998.[1]
They have been blamed for algal blooms and concerns exist they will outcompete and displace native species such as the montane pea clam (Pisidium spp.) and the ramshorn snail (Planorbidae). Efforts are underway at Lake Tahoe to smother the clams on the bottom with rubber mats.[43] In August 2020 routine inspections in Wyoming found several watercraft to be heavily infested including one with C. fluminea.[44][45] On October 16, 2020 the Montana Department of Fish, Wildlife and Parks recommended that Lake Elmo — in Billings — be drained to dry out and freeze to death the C. fluminea there.[46][47][48]
Corbicula fluminea is a species of freshwater clam native to eastern Asia which has become a successful invasive species throughout North America, South America, and Europe. Corbicula fluminea is commonly known in the west as the Asian clam or Asiatic clam. In Southeast Asia, C. fluminea is known as the golden clam, prosperity clam, pygmy clam, or good luck clam.
