Horseshoe Crabs Overview

Horseshoe Crabs

• Horseshoe crabs are marine invertebrates with eight legs and a hard exoskeleton, more closely related to spiders than crabs.
• They have remained largely unchanged for over 300 million years, predating dinosaurs.
• Four species exist: Atlantic, Mangrove, Coastal, and Chinese.
• Horseshoe crabs are found in salt water along coastlines, with egg-laying occurring on sandy beaches for protection.
• Juvenile horseshoe crabs inhabit shallow, protected areas like estuaries for the first two years.
• Adults are found in depths ranging from 100 to over 600 feet, spending most of their time on the sandy ocean floor.
• They can swim, but primarily walk along the ocean floor, where their food sources are located.
• The Atlantic horseshoe crab is found on the Gulf and Eastern Atlantic coasts of the United States, from Texas to Maine.
• The Mangrove and Coastal horseshoe crabs inhabit the Indian and Pacific Oceans, along the coasts of Southeast Asian countries.
• The Chinese horseshoe crab is found in the Eastern Pacific Ocean, along the coasts of East and Southeast Asia.
• Horseshoe crabs are omnivores, feeding primarily on worms and mollusks, particularly clams.
• They use their small front claws to grab food and move it to their mouth, which is equipped with bristles and plates for crushing and chewing.
• Horseshoe crabs utilize bristly plates in the center of their body for feeding.

Horseshoe Crabs - Ancient Relatives of Spiders

• Oldest Living Species: Horseshoe crabs have remained basically the same for around 300 million years, predating dinosaurs.

• Physical Characteristics: Marine animals with eight legs, a hard shell, and a body structure related to spiders.

• Distribution: Found in Atlantic, Indian, and Pacific Oceans, with four different species.

Habitat and Lifestyle

• Marine Life: They inhabit salt water, ranging from coastal beaches to depths over 600 feet.

• Life Cycle: Horseshoe crab eggs are laid on sandy beaches for protection. Juveniles live in shallow, protected areas like estuaries until maturity. Adults can live in deeper water, spending most of their time on the ocean floor.

• Movement: They are primarily bottom-dwellers, walking along the sandy floor where they find food. They can swim but usually prefer walking to keep their hard upper shell protected.

Species and Locations

• Atlantic Horseshoe Crab (Limulus polyphemus): Found along the Gulf and eastern Atlantic coasts of the United States, from Texas to Maine.

• Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda) and Coastal Horseshoe Crab (Tachypleus gigas): Similar geographic ranges in the Indian and Pacific Oceans, along the coasts of India, Indonesia, Malaysia, Singapore, and the Philippines.

• Chinese Horseshoe Crab (Tachypleus tridentatus): Found in the eastern Pacific Ocean, along the coasts of China, Japan, Taiwan, Malaysia, South Korea, Vietnam, and the Philippines.

Diet

• Ocean Floor Scavengers: Horseshoe crabs primarily feed on worms and mollusks, with clams being a common source.

• Feeding Mechanism: They grab food with front claws, transport it to their mouth, crush it with hard plates, and use bristly plates to "chew" it before sending it to their stomach.

Explore the fascinating world of horseshoe crabs, marine invertebrates that have existed for over 300 million years. Learn about their anatomy, habitat, and the four different species. This quiz will test your knowledge on these ancient sea creatures and their unique adaptations.