Crustaceans and mollusks are mainly aquatic invertebrates characterized by their soft bodies and shells, which are important for protection. Crustaceans and mollusks dwell in marine environments with some mollusks dwelling in freshwater while others are terrestrial. Crustaceans and mollusks are important subjects of aquaculture and as cuisine. However, in some areas, these invertebrates are regarded as an ecological menace due to the damage they cause in these ecosystems. Some of the notorious invasive mollusks and crustaceans include
11. Mnemiopsis leidyi
The sea walnut (Mnemiopsis leidyi) is a species of comb jelly native to the western Atlantic. The carnivorous sea walnut is invasive in the Black, Caspian, North, and Baltic seas. The sea walnut was introduced outside its range through ballast water in ships. Where the sea walnut invades, it leads to a disruption in the ecosystem and decline in the population of native species. In the Black Sea, it led to the decrease in the population of the European anchovy, a commercially important pelagic fish.
10. Carcinus maenas
The littoral crab (Carcinus maenas) or shore crab is a crustacean species native to the Baltic Sea and the northeastern section of the Atlantic Ocean. The littoral crab has invaded the waters of Australia, South Africa, South America, and North America. The crab is dispersed through shipping equipment during water transport and by ocean currents. The littoral crab causes the decline of native bivalve mollusks on which it feeds thus affecting the local fisheries and hence the economy. The crab also creates competition with other native species and sometimes feeds on juvenile oysters reducing their populations significantly.
9. Cercopagis pengoi
The fishhook waterflea (Cercopagis pengoi) is a crustacean native to the brackish waters of the Caspian Sea and the Black sea. The fishhook waterflea is one of the top 100 worst invasive species in the world. The fishhook waterflea was introduced to non-native areas through ballast water into freshwater systems. Being predatory, the fishhook waterflea competes with planktivorous invertebrates. The fishhook waterflea reproduces sexually and asexually thus population growth is extremely high. Their eggs are easy to disperse to other water as they stick on to boats and other fishing infrastructure.
8. Eriocheir sinensis
The Chinese mitten crab (Eriocheir sinensis) is a crab native to rivers and coasts of eastern Asia. The crab is an invasive species in Europe and North America. The crabs were introduced through ballast water in commercial ships. Out of its native range, the crab competes for resources with the native species, damages embankments by burrowing, and causes blockages to drainage systems. In Germany, the Chinese mitten crab causes damage to fishing nets, infrastructure, local dams, and the native fish. Control measures include legislation against the introduction of these crabs and restrictions of their fishing in different states.
7. Dreissena polymorpha
The zebra mussel (Dreissena polymorpha) is a native species of the lakes in southern Ukraine and Russia. The zebra mussel is currently an invasive species worldwide and ranks among the top 100 worst invasive species according to IUCN. The zebra mussel is invasive in Ireland, Great Britain, North America, Spain, and Sweden. Zebra mussels have led to the extinction of two species of freshwater mussels in Ireland. The zebra mussel by attaching on the bodies of native clams, reduce their ability to move thus causing their deaths. Other effects of the zebra mussel invasion include the destruction of harbors and waterways, blockage of pipes and damage to ships and boats.
6. Euglandina rosea
The cannibal snail (Euglandina rosea) is a medium-sized carnivorous land snail native to Central America and the south of the US. The snail was introduced in several areas including Hawaii as a biological control for the African land snail. However, this voracious predator instead became an invasive species in the regions. The cannibal snail has led to the further decline of native snail species. In Hawaii alone, the snail is responsible for the extinction of eight native snail species. Control measures for the snail include chemical and biological control, collecting the snails, and legislation banning the introduction of the cannibal snail.
5. Lissachatina fulica
The giant African snail (Lissachatina fuica) is a large land snail native to East Africa. The snail is one of the most invasive snails found anywhere, and was introduced to other areas as food, through pet trade, and accidentally in some areas. Where the snail has invaded, it causes severe damage to crops leading to massive losses. Apart from feeding on the plants, the snail introduces pathogens, which lead to plant diseases. The snail also competes with other native snail species thus affecting their populations. The snail is a worldwide menace since it adapts easily to different habitats.
4. Mytilus galloprovincialis
The Mediterranean mussel (Mytilus galloprovincialis) is a marine mollusk invasive worldwide. The Mediterranean mussel is found in the temperate and subarctic coasts of the Mediterranean and Black seas, the Atlantic Ocean, the northern Pacific, and in Russia, China, North Korea, and Japan. The Mediterranean mussel became dominant along the west coast of Europe as from the 1980s.
3. Pomacea canaliculata
The channeled applesnail (Pomacea canaliculata) is a large freshwater snail and one of the most invasive mollusk species. The snail is naïve to the tropical and subtropical regions of South America including Argentina, Paraguay, Uruguay, and Bolivia. The species is invasive in Southeast Asia, and Hawaii. The species has been located in the US, China, and Chile. In areas where it is introduced, the snail destroys rice and taro farms, therefore, affecting agriculture negatively. In these farms, the snail also displaces the native snail species, which also form a food source for the local people.
2. Potamocorbula amurensis
The overbite clam (Potamocorbula amurensis) is a saltwater mollusk native to the northern Pacific Ocean. The native range of the overbite clam is the Amur River in Siberia, China, Japan, and Korea. The overbite clam is an invasive species in San Francisco Bay. The clam invaded the waters of San Francisco Bay in the 1980s and has currently grown exponentially in its population. This population growth creates high competition with native species. The overbite clam also feeds on planktons, which juvenile fish rely on thus disrupting the food web of the bay.
1. Asterias amurensis
The northern Pacific seastar (Asterias amurensis) is a starfish native to Korea, Russia, northern China, and Japan. The starfish is an invasive species in Australia introduced through transport in ballast water for ships. In Australia, the starfish has invaded the Derwent estuary and the Henderson Lagoon. The starfish pose high risks to the economy, human health as well as other marine populations where the northern Pacific seastar invades. The starfish has, for instance, contributed significantly to the decline of handfish, which is an endangered species. Several control methods have been tried including chemical and biological control as well as physical removal. Physical removal was found to be the most effective method, which does not create any changes to the ecosystem.
About the Author
Benjamin Elisha Sawe holds a Bachelor of Arts in Economics and Statistics and an MBA in Strategic Management. He is a frequent World Atlas contributor.
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