
Horseshoe crabs coming ashore in Delaware Bay © Gregory Breese/USFWS
We’ve posted about them before, but did you know that horseshoe crab blood is not only a powder blue color, but also is used in the medical industry to detect any trace of bacterial contamination in humans, even if that infection is only one part per trillion? And that they are more closely related to scorpions than true crabs? Or that they’ve been having the longest-running mass-breeding efforts on the planet, given that they haven’t changed much in hundreds of millions of years? Marah Hardt writes for The Nature Conservancy on the importance of these crawling Chelicerates to their ecosystem:
The lapping waves and silent dunes of the Delaware Bay shoreline create a perfect backdrop for a moonlit summer stroll. But a few weeks ago, this beach was not nearly so quiet. Instead, the silver light of the full moon shone upon jostling crowds of horseshoe crabs.
“If the crabs were rocks,” says Moses Katkowski, marine conservation coordinator with The Nature Conservancy, “you could walk on their backs the entire stretch of beach and never touch the sand.”

















