物競天擇、適者生存，大自然各樣物種會隨着環境轉變而演進，若然未能適應，便會步向滅亡。然而，比恐龍還要早出現在地球上，已經繁衍了四億年的馬蹄蟹，其基本體形多年來都沒有大改變，牠一直存活到今天，確是名副其實的活化石。
又稱鱟的馬蹄蟹，牠並非蟹類，而是蜘蛛和蠍子的近親。幼體馬蹄蟹在淺灘生活，靠蠕蟲、甲殼類動物維生，經歷多次脫殼，約十年後，才能成長為鱟。外貌奇特的馬蹄蟹其實是人類的好朋友，以其血液加工製成的試劑，被廣泛用於藥物及醫學上的無菌檢測；其外殼中高純度的甲殼素，更會被用於外科手術的縫合線，及用於污水處理上，幫助吸附水中的懸浮物質和毒性有機物。
然而，在缺乏保育法規的中國，馬蹄蟹的優點反成為被大量捕殺的誘因，所以數量正不斷減少。在香港，隨着都巿發展及人為帶來的干擾，馬蹄蟹的生存空間亦變得越來越狹窄！
Horseshoe crabs, so called "living fossils", have been on Earth for hundreds of millions of years. How horseshoe crabs make their living? We have made a video which recorded horseshoe crabs' eating, moulting and mating behaviour. The video provides an opportunity for people to have a good look at horseshoe crabs' life.
Horseshoe crab blood is a vital resource to the medical field. It's unique in more ways than one: the blue color and its ability to identify bacterial contamination in small quantities. Horseshoe crab blood contains a special amebocyte that is separated and then used in FDA testing. There's a lot of questions as to how blood harvesting affects the American horseshoe crab population, but some researchers are dedicated to the cause of protecting such a significant resource.