It has swum the waters of the earth for 400 million years, predating mankind and even the dinosaurs, but now the peculiar horseshoe crab is facing its biggest survival challenge. Pollution and the development of shorelines in Hong Kong is destroying the spawning and nursery grounds of the crab, one of the world’s oldest and strangest-looking creatures, and in turn is drastically affecting its population. A recent study by the City University in Hong Kong detected one or two crabs on every 1,000 square metres of seabed compared to 10 to 20 per 1,000 square metres in 2002 - a decrease of 90 per cent in four years. Biologist Paul Shin Kam-shing, who led the study, said that in the 1980s and 1990s, Hong Kong had been home to three of four known species of the horseshoe crab, but recent studies found only two species remained, with one of these in very low numbers. The biggest threat to the survival of this species, said Shin, a professor at City University in Hong Kong, is quite simply the development and pollution of the shoreline where the crab lays its eggs and also spends its early years. Disturbing, destroying or polluting the shorelines is likely to reduce their chances of survival even further.