Little is known about the horseshoe crabs in Asia, other than the fact that they suffer from an identity crisis. They may be called crabs, but these ancient animals are actually more closely related to arachnids - a group that includes spiders.
The Nature Society (Singapore) or NSS, however, is on a mission to find out more about these animals in a bid to conserve them better, by collecting data about native populations and urging countries that have them to do the same.
There are four species of horseshoe crabs found around the world, three of which can be found in Asia.
But the three species - coastal, mangrove and Chinese horseshoe crabs - are considered data deficient on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, which means not enough is known about them to classify how close to extinction they are.
The Atlantic horseshoe crab, found in the Americas, is the only species with an international classification - it is considered vulnerable to extinction, having been harvested for its blood, which is used in the pharmaceutical industry.
"More information is needed to reassess the status of the three Asian horseshoe crab species, which live in fast-disappearing mudflat and mangrove habitats, " said NSS volunteer J. Vanitha, who was in Hawaii last month to speak about the society's ongoing horseshoe crab rescue and research programme at the IUCN World Conservation Congress.
In Asia, these animals are threatened with habitat loss as mudflats and mangroves make way for development.
In 2012, the NSS proposed to IUCN, the international body in charge of classification, that there was a need to review the status of Asian horseshoe crabs and encourage cooperation between countries which have the Asian horseshoe crabs to conserve the habitats.
Their proposal was accepted and the society is now working to collect data on two of the three Asian horseshoe crab species found in Singapore - the coastal and mangrove horseshoe crabs.
NSS is also in talks with naturalists and scientists in neighbouring countries - such as Malaysia, which has all three Asian horseshoe crab species - on how they can get involved in the effort to reassess the status of the Asian horseshoe crabs.
One way to do this is to enlist the help of citizen science volunteers, which NSS has been doing, said Ms Vanitha, 35, a teacher.
Since 2005, NSS volunteers have been venturing out to the Mandai mudflats - a coastal habitat near Sungei Buloh - on a monthly basis to rescue horseshoe crabs entangled in prawn nets. But the programme expanded in 2007, when volunteers realised they could use the opportunity to measure, record and study the horseshoe crabs.
Mr Stephen Beng, chairman of the NSS' Marine Conservation Group, said horseshoe crabs have an important place in the marine food chain. Their eggs and young, for instance, provide food for birds that stop by the Mandai mudflats.
He added: "Horseshoe crabs are a flagship species of mudflats and mangroves, and citizen science programmes like ours can help raise awareness about the significance of their habitats - less than 1 per cent of Singapore remains covered with highly diverse and productive mangroves."
Students from Republic Polytechnic's (RP) Diploma in Environmental Science are also working on rearing mangrove horseshoe crabs in captivity to gain insights into their breeding cycle, with the intention of breeding them until they reach the reproductive stage and then releasing them into areas where they were once abundant.
Dr Linus Mak, a lecturer from the Diploma in Environmental Science programme at RP's School of Applied Science, said: "It will offer insight into the local species, the threats they face, breeding and conservation methods, and help bridge the gap in data deficiency."
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Learn more about the horseshoe crab