Horseshoe crabs do not bite or sting. These ancient marine arthropods, which predate the dinosaurs, possess an intimidating appearance but are harmless to humans. Despite their common name, they are not true crabs, belonging instead to a group more closely related to spiders and scorpions. Their unique biology and feeding mechanisms prevent them from biting, and their long, spiked appendage is not a weapon.
Anatomy and Feeding
The horseshoe crab is incapable of biting because it lacks anatomical structures like jaws or teeth. Its mouth is located centrally on the underside of its body, positioned between its six pairs of appendages. Food must be brought inward toward the center of the body rather than using an external biting force.
The feeding process relies on the base of its walking legs, which are equipped with inward-pointing spines called gnathobases. As the animal walks along the seafloor, these gnathobases move and grind together, crushing food items such as soft-shelled mollusks and marine worms. This crushing action macerates the food before it reaches the mouth opening.
Small, pincer-like appendages called chelicerae are positioned in front of the mouth. They are used primarily to grasp and push the pulverized food into the oral cavity. The horseshoe crab essentially chews its food with its legs. The weak nature of its small chelicerae means they lack the strength to inflict injury on a person.
The Function of the Telson
The horseshoe crab’s long, spiked tail is scientifically known as the telson. This appendage is frequently mistaken for a stinger, but it contains no venom and is not used for defense. The telson is a rigid but movable extension of the abdomen.
The primary purpose of the telson is to act as a rudder, assisting the animal in steering while navigating the water column. More importantly, the telson is a self-righting mechanism. If a horseshoe crab is overturned by a wave or strong current, it uses the telson as a lever to push against the substrate and flip itself back onto its feet.
This function is vital for the animal’s survival, as being stranded upside down makes it vulnerable to desiccation and predation. Because the telson is important for movement, it is delicate and can be easily damaged if handled incorrectly.
Safety and Human Interaction
Horseshoe crabs are completely harmless to humans and are not venomous or poisonous. While they may appear intimidating, the only caution necessary is to handle them gently and with respect for their delicate anatomy. The tail should never be used to pick up or carry the animal, as this can easily fracture the telson and compromise its ability to survive.
If you encounter a stranded horseshoe crab, you can safely assist it by grasping the edge of the shell, or prosoma, with both hands. Gently turn the animal over and place it back on its legs, directing it toward the water. Avoid placing fingers near the hinge where the shell segments connect, as this area moves and could cause a slight pinch.
It is common to see these creatures on beaches during the late spring and early summer when they come ashore to spawn at high tide. Observing them respectfully and assisting any that are stranded is the best way to interact with these living fossils.