Horseshoe crabs are ancient and unique marine creatures that have roamed Earth’s waters for hundreds of millions of years. Often encountered along coastal shores, their armored appearance sometimes leads to questions about their safety. Many people wonder if these prehistoric-looking animals are poisonous or pose a danger to humans. Understanding more about these fascinating invertebrates can help clarify common misconceptions.
Dispelling the Poisonous Myth
Despite their intimidating appearance, particularly their long, pointed tail, horseshoe crabs are not poisonous or venomous. The common misconception often arises from their sharp, spear-like telson, the appendage at the rear of their body. This telson is not a stinger and does not contain venom or poison.
The telson serves primarily as a tool for movement and self-righting. If a horseshoe crab gets overturned, it uses its telson to flip itself back upright. While the telson can feel sharp, it is not used for aggression or to inject toxins.
Understanding Horseshoe Crab Biology
Horseshoe crabs are not true crabs but are more closely related to arachnids like spiders and scorpions. They belong to the family Limulidae and are often called “living fossils” because their form has remained largely unchanged for over 445 million years. Their body is divided into three main sections: the prosoma (the large, horseshoe-shaped front section), the opisthosoma (the middle, segmented abdomen), and the telson (the tail).
These animals possess a hard exoskeleton that provides protection, and they grow by periodically shedding this outer shell in a process called molting. They have multiple eyes, including two large compound eyes on their prosoma, which help them sense light. Horseshoe crabs breathe using book gills located on the underside of their abdomen. They are bottom-dwelling scavengers and omnivores, primarily feeding on worms, clams, small crustaceans, and algae found in sandy or muddy coastal waters. Horseshoe crabs are docile and non-aggressive, relying on their protective shell and ability to burrow into sand for defense.
Safe Interactions with Horseshoe Crabs
Encounters with horseshoe crabs are common along coastlines, especially during their spring and summer spawning seasons when they come to shallow beaches to lay eggs. Observing them from a distance is the safest way to appreciate these unique creatures. The telson can cause a superficial poke or scratch if handled carelessly, so avoid direct contact.
If you find a horseshoe crab stranded upside down on the beach, you can assist it. Gently pick up the crab by the sides of its prosoma, holding both sides of its shell, rather than by its tail. Then, carefully place it right-side up in the water, pointing towards the ocean. These animals are important to both the ecosystem, serving as a food source for migratory birds and other marine life, and to medical research. Their unique blue blood contains a substance called Limulus Amebocyte Lysate (LAL), which is used globally to detect bacterial contamination in vaccines, injectable drugs, and medical devices, ensuring their safety for human use.