Chinese mitten crab

Description

The Chinese mitten crab also known as the Shanghai hairy crab is a medium-sized burrowing crab that is named for its furry claws, which resemble mittens. It is native to rivers, estuaries and other coastal habitats of East Asia from Korea in the north to Fujian, China in the south. It has also been introduced to Europe and North America, where it is considered an invasive species. The species features on the list of invasive alien species of Union concern. This means that import of the species and trade in the species is forbidden in the whole of the European Union. This species' distinguishing features are the dense patches of dark setae on its claws. The crab's body is the size of a human palm. The legs are about twice as long as the 3-10-centimeter-wide (1-4 in) carapace. Mitten crabs spend most of their life in fresh water and return to the sea to breed. During their fourth or fifth year in late summer, the crustaceans migrate downstream and attain sexual maturity in the tidal estuaries. After mating, the females continue seaward, overwintering in deeper waters. They return to brackish water in the spring to hatch their eggs. After development as larvae, the juvenile crabs gradually move upstream into fresh water, thus completing the life cycle. It moves from freshwater habitats to saltwater habitats once it has reached reproduction maturity. The types of estuaries suitable for the mitten crab is large brackish waters for the larva to develop in, and large shallow waters for the growth of the juvenile crabs. An increase in microplastics has had a significant impact on the population as it affects their metabolism, growth, and oxidative stress response in the liver. The Chinese mitten crab originates from Hong Kong to the border of Korea. It can be found inland but prefers coastal areas. In the Yangtze, the largest river in its native range, Chinese mitten crabs have been recorded up to 1,400 km (760 nmi) upstream. It is known to settle in rice fields by the sea and rivers inland. The crab is found in subtropical and temperate regions. Phylogenetically the crab belongs to the Varunidae family which is the newest group of brachyuran crustaceans. Spawning crabs average around 5.5 cm (2+1⁄4 in) in length. Since crabs spawn at the end of their life spans and perish at the end of the breeding cycle, the crabs can live up to 7 (in Germany also 8) years old.