"Eeew! It looks like an alien."

"What are they?" a child whispers nervously to her mother, pointing at the brightly-lit tanks of live seafood, displayed meters away from the promenade at Sai Kung. Passers-by stop to look at five strange creatures with helmet-like khaki-colored shells and long spiny tails huddled on the ground.

An elderly man uses his walking stick to flip over one of these, revealing several pairs of wriggling legs and fly-type compound eyes, causing a teenager to jump.

It's a horseshoe crab, one of Hong Kong's oldest native marine species, in fact.

Fossilized remains of the horseshoe crab show it has been around since 475 million years, some 230 million years before dinosaurs roamed the earth. It has survived up to six major extinctions, including the great Permian extinction that wiped out 95 percent of all marine species. Moreover, it has remained largely unchanged, the reason it's called a "living fossil".

Yet despite its proven ability to outlive other species, the horseshoe crab now faces its biggest survival challenge.

Research by the City University of Hong Kong shows the population of juvenile crabs fell by about 90 percent between 2002 and 2009, leaving only about 10,000 in 2012.

A population study conducted this summer is expected to show a greater decline, according to Paul Shin Kam-shin.

Shin, who led the study, believes the fall in numbers does not bode well. He feels intervention is needed to guarantee the survival of the horseshoe crab, not listed among the protected species.

"Okay, the horseshoe crab is not cute like the giant panda but it is worthy of protection," said Shin, of the university's Department of Biology and Chemistry.

For one, it's useful in medicine. A protein in the horseshoe crab's blood, which is in fact blue, called Limulus Amoebocyte Lysate, is used in the pharmaceutical industry for detecting bacteria in injected medications. Its tough shell is made of chitin: a substance used to make surgical thread, contact lenses, skin creams and remove certain harmful chemicals from water.

"The horseshoe crab also has an ecological role to play," says Shin. "On the seabed, the adults search for food by digging in the mud. When they dig, they are like buffalo ploughing the land. The disturbance they create releases nutrients from the mud back into the water.

"The crab is also a food for larger sea life. In the United States their eggs are a good source of food for an endangered migratory bird called the Red Knot."

There are four types of horseshoe crabs left in the world, Hong Kong being home to two of them: the Chinese horseshoe crab and the mangrove horseshoe crab. Despite their name, they are not crabs at all, rather a species more closely related to the scorpion or spider.

According to Shin, the pollution of sea water and disturbances of shorelines are major threats to the horseshoe crab, harming the spawning and disturbing the nursery ground of the crab, which spends its first 10 years on the sand and mudflats before moving to the seabed.

It also makes a fine dish in certain parts of Asia, although less so in Hong Kong, says Shin.

Since 2006, Shin and a team of scientists at the City University of Hong Kong have been working with Ocean Park Conservation Foundation (OPCF) on a project to protect the horseshoe crab from extinction.

The scheme involves artificially breeding and rearing horseshoe crabs, later released in the waters to boost the population. In summer this year, the university, the OPCF and about 760 secondary school students took part in a population survey aimed at providing more data which researchers hope will give an indication of whether it is seriously under threat.

Joe Cheung, OPCF's assistant manager of community education, said more than 1,000 baby horseshoe crabs were released under the program since 2009. Some of these, which have been micro-chipped, were picked up in subsequent population studies and showed positive growth.

In 2012, a specialist group, including Shin and Hong Kong expert Kevin Laurie, was set up by International Union for Conservation of Nature to try and gather more authentic data on horseshoe crabs as a first step towards developing comprehensive conservation strategies for all four species.

In the meantime, Shin believes Hong Kong can do its bit by protecting bays which are known spawning and nursery grounds and improving public awareness of this valuable creature.

"Hong Kong should consider itself lucky to be home to two of the last remaining species of horseshoe crabs," said Shin. "We have to change people's minds about it and persuade the government to look at habitat protection before it is too late."

OPCF's Joe Leung agrees. "These animals are of biological and ecological significance. They have survived five or six great extinctions and now they are being threatened by humans. That's not good."

The horseshoe crab, one of HK's oldest marine species, is likely to go extinct unless its habitat is protected. Provided to China Daily

(HK Edition 11/26/2014 page7)