Atlantic Horseshoe Crab

Overview

The Atlantic horseshoe crab is a unique marine chelicerate, more closely related to spiders and scorpions than to true crabs. Often called a "living fossil," this species has remained largely unchanged for millions of years and serves as a vital component of coastal ecosystems.

Distribution & habitat

This species is found along the Atlantic and Gulf coasts of North America, ranging from Maine to the Yucatan Peninsula. They are benthic animals that inhabit both estuarine environments and the continental shelf. While they spend much of their lives in deeper offshore waters, they migrate to protected, sandy intertidal beaches to spawn.

Appearance

The body is divided into three distinct sections: the large, horseshoe-shaped cephalothorax (prosoma), the abdomen (opisthosoma), and a long, pointed tail called a telson. They possess multiple eyes, including lateral compound eyes and simple eyes on the prosoma, along with additional photoreceptors on the abdomen and telson.

Biology & behavior

Horseshoe crabs are long-lived, reaching sexual maturity between 9 and 12 years of age. They must molt their hard exoskeleton to grow, a process that occurs repeatedly until they reach maturity. While they typically crawl along the seafloor, they are capable of swimming upside down by using their flap-like gills as paddles.

Feeding

As nocturnal foragers, they feed on a variety of bottom-dwelling organisms. Their diet primarily consists of marine worms, small molluscs, and decaying organic matter, which they grasp and crush using specialized appendages called chelicerae.

Reproduction

Spawning typically occurs in the spring and summer, often coinciding with high tides during new and full moons. Adults congregate on sandy beaches, where females deposit eggs in the sand to be fertilized by males. The eggs hatch into larvae that eventually move into intertidal flats as they develop.