Oldest crustacean [Form]
Last updated: October 13, 2017 at 0:21 am
The horseshoe crab (Limulus polyphemus) has existed in its current form for the past 135 million years. Approximately 500,000 horseshoe crabs are harvested annually for their copper-rich blue blood, which uses hemocyanin instead of hemoglobin to carry oxygen. Amebocytes found in the blood is used to make Limulus amebocyte lysate, which is used to detect bacterial endotoxins in medical applications. Most horseshoe crabs survive the harvesting and subsequent release back into the sea. The ancestors of the horseshoe crab can be traced back to around 445 million years ago, or 200 million years before dinosaurs first appeared. They are thus considered living fossils.