Horseshoe crab is an ancient marine creature which has existed since the Late Ordovician Period (475 million years ago), about 230 million years earlier than the early appearance of dinosaurs. The morphology of horseshoe crab has not changed much over the years; thus, the species is being named as “living fossil”. Being one of the oldest species on the planet, horseshoe crabs are also of great value in evolutionary history and biology.
Horseshoe crabs depend on mudflat and mangrove heavily as habitats to forage and grow; however, habitat destruction is severely threatening their juveniles. On the other hand, adult horseshoe crabs in China, Thailand, and Vietnam have been affected by threats such as large-scale fishing for food and blood collection as medical testing reagents. In March 2019, the IUCN Red List of Threatened Species listed one of the species found in Hong Kong, Chinese horseshoe crabs, as Endangered, reflecting the urgent need to conserve them.