Horseshoe crab relations will be heating up across the coast of Florida this March and April, as mating season hits for the bizarre living fossil. As a vital component of both the marine ecosystem and medical science, declining population numbers in recent years have come as a cause of great concern for conservationists and practitioners alike. To track the health of these incredible creatures, Florida wildlife services are asking you to spill the tea on any horseshoe crabs you see getting down n’ dirty.
The name horseshoe crab is actually a misnomer, as these armored arthropods aren’t a member of the crustacean subphylum but instead Chelicerata. As one of the major subdivisions of arthropods, Chelicerata includes the arachnids and scorpions and while most of its members look a bit freaky, horseshoe crabs are surely the freakiest of them all.
Found in and around shallow coastal waters, horseshoe crabs have adapted to life on the seafloor with a mouth that sits between five pairs of legs with gnathobases (used for crushing food), making their underside look like something out of Alien. Their entire body is protected by a rock-hard carapace, which keeps them safe from aerial attackers. Having diverged around 445 million years ago, they’re considered living fossils and are closely related to the extinct Eurypterids (sea scorpions), which included some of the largest arthropods ever to have existed.
As food for fish, sea turtles, and alligators, horseshoe crabs are an important part of the food chain and their eggs support migrating birds. As such, their dwindling numbers in recent years as a result of habitat loss and human interaction could spell disaster for a wealth of species. Unfortunately, the IUCN Red List categorizes them as vulnerable and population trends show their numbers are still decreasing.
For years they were harvested ruthlessly for their bizarre blue blood, an exploitation that was later sanctioned so that only 30 percent of their blood could be taken before returning them to the water, but around 30 percent don’t survive this process. It’s one of the most expensive natural products in the world and costs $60,000 a gallon, so valued because it contains the components needed to make LaL, which is used to test for gram-negative bacteria in and on all injectable vaccines and medical instruments.
Wildlife services are enlisting the help of citizen scientists so that biologists can gain a better understanding of where and when horseshoe crabs are spawning in Florida. The demand for horseshoe crabs matched with their dwindling numbers has resulted in many states putting restrictions on horseshoe crab harvesting. The Atlantic States Marine Fisheries Commission (which manages horseshoe crabs on a federal level) developed the Horseshoe Crab Fishery Management Plan, which requires all Atlantic coastal states to identify horseshoe crab nesting beaches.
You can help by reporting any sightings of mating pairs or females laying their eggs which, like sea turtles, come onto the beach to do so. You can easily spot their baby-making as many males will flock to a single female, hoping to hook on and fertilize her eggs. The female horseshoe crabs are larger, and you’ll most likely spot them in the act during high tide within a few days of a new or full Moon. Also, if you see a horseshoe crab on its back don’t be afraid to flip it – just take care to only lift by their carapace and avoid the tail. You can report your sightings to the Florida Fish and Wildlife Conservation Commission here.
