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Corbicula fluminea is a species of freshwater clam, an aquatic bivalve mollusk in the family Corbiculidae.
This species is of originally mainly Asian origin and thus it is often commonly called Asian clam or Asiatic Clam In the aquarium and koi pond trade it is often called Golden Clam or Golden Freshwater Clam. In Southeast Asia it is known as the prosperity clam or good luck clam.
This species has been introduced into many parts of the world, including North America and Europe.
Right after reaching maturity these clams produce eggs, followed by sperm. Even later, they produce eggs and sperm simultaneously. They can self-fertilize, and release up to 2,000 juveniles per day, and more than 100,000 in a lifetime. Juveniles are only 1mm long when discharged, and take one to four years to reach maturity. At this time they are about one centimeter long. Adults can reach a length of about 5 cm.
The outside of the shell is normally yellow-green with concentric rings. The color can flake, leaving white spots. The shells are lightly purple on the inside.
They feed primarily on phytoplankton (algae), which they filter from the sandy or muddy bottom of streams, lakes, or canals.
"An invasive clam, Corbicula fluminea, appeared at Lake Tahoe in 2002 in spotty numbers. But in the past two years, densities of the inch-long clam have jumped 100-fold. Waste from the clams, in turn, has helped trigger blooms of bright green algae"[1]. Researchers have recently found that since the early 1990's Lake Tahoe and other California and Nevada lakes have been warming at twice the rate of the surrounding atmosphere.[2]. The USGS has concluded, C. fluminea is likely to continue to expand it's North American range until it reaches it's lower temperature tolerance.[3]
Recently German researchers have determined that a "strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere." [4]
The primary economic/social impact of the invasion of C. fluminea has been billions of dollars in costs associated with clogged water intake pipes, associated with power plants, among others. Ecologically C. fluminea contributes to declines and replacement of highly vulnerable, already threatened native clams. [5].
Distribution
As a native species
This clam originally occurs in Russia, Thailand, the Philippines, China, Taiwan, Korea, Japan, but also in parts of Africa.1
As an invasive species
C. fluminea was probably brought to North America at the latest in 1924, by Asian immigrants who used the clams as a food source. The clams are abundant in the Albemarle region of North Carolina, as well as other areas along the east coast.
It was first found in the Rhine in the late 1980s and subsequently found its way into the Danube through the Rhine-Main-Danube Canal. It reached the Elbe in 1998 at the latest.2 It is non-indigenous in Elbe in Bohemia (Czech Republic) since 20003 and it is spreading,.4 is now in rivers of Portugal, like Minho River.
Taxonomy
There are in fact two species present in introduced populations, C. fluminea and Corbicula fluminalis5. However, the two species are often mixed together. The names themselves are sometimes confused in the literature (e.g. by being called '"Corbicula fluminata"). Care needs to be taken in order to properly distinguish the two species.
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 amount of ribs on the shell; C. fluminea has 7 to 14 ribs per cm, C. fluminalis 13 to 286. This character is already clearly recognizable (albeit only by direct comparison) in very small (5 mm diameter) specimens. In addition, when viewed from the 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 (the oldest part of the shell valves, close to the ligament holding them together).
References
- ^ USGS (2001): Nonindigenous species information bulletin: Asian clam, Corbicula fluminea (Müller, 1774) (Mollusca: Corbiculidae). PDF fulltext
- ^ Jueg, U. & Zettler, M.L. (2004): Die Molluskenfauna der Elbe in Mecklenburg-Vorpommern mit Erstnachweis der Grobgerippten Körbchenmuschel Corbicula fluminea (O. F. Müller 1756). Mitteilungen der NGM 4(1): 85-89. [in German] PDF fulltext
- ^ Beran, L. (2000): First record of Corbicula fluminea (Mollusca: Bivalvia) in the Czech Republic. — Acta Soc. Zool. Bohem., 64: 1-2.
- ^ Beran L., (2006) Spreading expansion of Corbicula fluminea (Mollusca: Bivalvia) in the Czech Republic. – Heldia 6 5/6: 187-192.
- ^ It is not entirely clear that this is the correct name (Jueg & Zettler, 2004)
- ^ Jueg & Zettler (2004), and see "External links"
7. ^ Weitere, M. et al. (2009) Linking environmental warming to the fitness of the invasive clam Corbicula fluminea, Global Change Biology, Volume 15 Issue 12, Pages 2838 - 2851 [6]
External links
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