User:Sbrobbchavez/Corbicula fluminea

Overview

Corbicula fluminea is a species of freshwater clam, an aquatic bivalve mollusk in the family Cyrenidae. This species is often confused with Corbicula fluminalis due to the two species' similar colour and texture.

The species is regarded as having originated in Eastern Asia, leading to the common names of Asian clam or Asiatic clam. In the aquarium and koi pond trade, it is often called the golden clam or golden freshwater clam. In Southeast Asia, it is known as the prosperity clam or good luck clam. In Korea, the name is 재첩 (jaecheop, among other transliterations), and the species (include Corbicula japonica, Corbicula leana) is used for a common dish called jaecheop-guk (clam soup).

Corbicula has enjoyed global success as an aquatic invasive species, having been introduced to a novel range including South America, 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.

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 1 mm long when discharged, and take one to four years to reach maturity. At this time, they are about 1 cm 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 bottoms of streams, lakes, or canals. According to the United States Geological Survey, C. fluminea is likely to continue to expand its North American range until it reaches its lower temperature tolerance.

The primary economic and social impact of the invasion of C. fluminea has been billions of dollars in costs associated with clogged water intake pipes of power plants, among others. Ecologically, C. fluminea contributes to declines and replacement of highly vulnerable, already threatened native clams. A market exists for Asian clams for human consumption in Japan, China, and other countries in the region (citation needed).

Distribution

As a native species

Asian clams originated in the 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.

As an invasive species

Nearly all coastal rivers with a heavy industrial shipping presence on 6 continents (excluding Antarctica) have become invaded by the Asian clam (Citation needed). Notable nonindigenous populations of C. fluminea include:

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.
Czech Republic - in Elbe in Bohemia since 2000 and it is spreading.
Slovakia
It is now in rivers of Portugal, such as the Minho River, and was first recorded in Ireland in 2010.
Cuba
Lake Placid, NY, USA
Allegheny River, Pittsburgh, PA
River Nore & Barrow, Republic of Ireland, first recorded in April 2010
Lake Tahoe, on the borders of California and Nevada, they were first found in 2002, and the numbers increased rapidly after 2008. 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 to smother the clams on the bottom with rubber mats.
South America, including Argentina, Uruguay, Brasil (Río de La Plata basin, Río Amazonas Basin, Patagonia - Río Colorado, Río Negro- and is currently in expansion), Perú, Venezuela and Ecuador (Guayas, Daule, Vinces, Quevedo, and Babahoyo River drainages).

Global Invasion Pattern

By combing the scientific literature, researchers have reconstructed the global invasion pattern of the Asian clam. The first recorded instance of Corbicula presence in the western hemisphere was its introduction into British Columbia circa 1924, followed by a spread throughout the Pacific Northwest and across the American south down to South America. Invasions in Europe and Central America appear to be more recent, first appearing in Carribbean countries in 1998 (Citation: Crespo et al. 2015).

Invasive Success

Invasion Vectors

There is some evidence suggesting that Asian clams followed immigrant Asian communities to North America circa 1924 as a food source (original citation). Freshwater bivalves including Corbicula fluminea, found their chief transportation method around the world in shipping as ballast water taken in by large container ships, as an example, has transported Corbicula larvae from port to port with the rapid advent of globalized trade in tandem with lax international policy (Citation: Karatayev et al. 2007). The spread of Asian clams has been further exacerbated by other human activities such as the shellfish trade and accidental overland transport by recreational boaters bringing the clam into interior freshwater systems (citation: Karatayev et al. 2007).

Life History Advantages

Human activities are the chief vector responsible for Corbicula fluminea's global success as an aquatic invasive, however the Asian clam enjoys several physiological capabilities which are advantageous in promoting the invasion of novel lentic/lotic environments including:

Rapid individual growth rate
Short time to reach sexual maturity
Short lifespan paired with high fecundity
Fast rate of water filtration for suspension feeding
Ability to broadcast gametes over a broad area by utilizing water flow (in rivers)
Tolerance of a wide variety of substrate/habitat types (Citation here? Gomes et al. 2016)

Research has shown that Corbicula fluminea possesses a rare reproductive trait in that the clam may reproduce either sexually or asexually depending on conditions-this allows for the ability to colonize novel habitats at an advanced rate thanks to the interplay between certain asexually-produced paternal genetic lineages and sexually reproducing ones (Citation-Gomes et al. 2016).

Impacts on Invaded Ecosystems

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) reworks the sediments it resides on through the process of bioturbation. (citation: Majdi 2014). Asian clams are considered biodiffusors like marine clam species due to their observed bioturbation activity causing certain sediment particles to sink, which may have effects on other members of the benthic community in invaded areas (Majdi 2014)/

***will include a bit about threats to native bivalves when I find a good source***

Taxonomy

Corbicula fluminea vs Corbicula fluminalis

Two species are present in introduced populations, C. fluminea and C. fluminalis. 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 to properly distinguish the two species.

Corbicula fluminalis

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 growth rings on the shell; C. fluminea has 7 to 14 ribs per cm, C. fluminalis 13 to 28. 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.

Habitat association

Studies on what 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 increasing levels of organic matter are negatively correlated (citation:Silveira et al. 2016). Others in Portugal 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 course sand combine to explain 59.3% of Corbicula population habitat association via statistical tests (citation: Sousa et al. 2007). Asian clam invasions seem to limited by elevation, as well as the minimum winter temperature of the ecosystem (Crespo et al. 2015)

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