MANGROVE HORSESHOE CRAB
One of two horseshoe crab species that can be found in Singapore, usually in the mudflats that line the Republic's northern coast.
But it is considered "data deficient" on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. This means there is not enough available information, such as on its worldwide population size and distribution, to classify this animal.
In Singapore, scientists have determined that it is vulnerable to extinction, due to factors such as irresponsible fishing and habitat loss.
COASTAL HORSESHOE CRAB
This is the other horseshoe crab species that can be found here. Like the mangrove horseshoe crab, coastal horseshoe crabs are considered data deficient on the international level. In Singapore, scientists have classified it as an endangered species.
CHINESE HORSESHOE CRAB
The Chinese horseshoe crab is another Asian horseshoe crab species, but it cannot be found in Singapore.
It has, however, been discovered in places including China, Indonesia, Malaysia, Taiwan, the Philippines and Vietnam. On the IUCN Red List, this species is considered data deficient.
ATLANTIC HORSESHOE CRAB
The only horseshoe crab species of the four to be classified at the international level, it is considered vulnerable on the IUCN Red List. This could be because more studies have been done on it in the Americas, where it is found. Over there, Atlantic horseshoe crabs are actively harvested for their blue-coloured blood, which contains a chemical called coagulogen that can detect traces of bacterial presence and trap them in clots. Scientists use this to detect contamination.
•Sources: Nature Society (Singapore) , The Atlantic