Two thirds of freshwater crab species maybe become extinct
London: A new survey has indicated that two thirds of all species of freshwater crab maybe at risk of going extinct, with one in six species particularly vulnerable.
According to a report by BBC News, the study, which is the first global assessment of the extinction risk for any group of freshwater invertebrates, makes freshwater crabs among the most threatened of all groups of animals assessed so far.
Crab species in Southeast Asia are the most at risk, from habitat destruction, pollution and drainage.
Scientists from the Zoological Society of London and Northern Michigan University led the survey, which produced the first World Conservation Union (IUCN) Red List assessment of the 1280 known species of freshwater crab.
Of those, the survey found that 227 species should be considered as near threatened, vulnerable, endangered or critically endangered.
For another 628 species, not enough data exists to adequately assess their future.
However, while the most optimistic scenario is that 16 percent of all species are at risk, the worst-case scenario suggests the figure could be as high as 65 percent, or two-thirds of all species.
Freshwater crabs are essential to many freshwater ecosystems. Some feed on fallen leaves and algae, while other species help cycle nutrients by eating vast quantities of detritus.
The crabs themselves are an important source of food for a range of birds such as herons and kingfishers, reptiles such as monitor lizards and crocodiles and amphibians such as frogs and toads.
Mammals that like to dine on freshwater crabs include otters, mongooses, civets as well as wild boar and even macaque monkeys.
Because most species require pristine water to survive, they are also excellent indicators of good water quality.
But, species are increasingly being impacted by habitat destruction and pollution.
The Singapore freshwater crab lives on an island, making it particularly vulnerable to disturbance and pollution
Most vulnerable are crabs living in Southeast Asia, which is also home to the greatest diversity of species.
For example, 40 of 50 species living in Sri Lanka are threatened.
Those species that live a semi-terrestrial life, breathing air, living in burrows and dividing their time between water and land, appear most at risk, possibly because their habitats are most easily disturbed by human activities.
No species are yet known to have gone extinct, but some species such as the terrestrial crab Thaipotamon siamese and the waterfall crab Demanietta manii from Thailand have not been seen alive for over a century, and their original habitats have since been built over by urban developments.
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