Horseshoe Crab: Ancient Marine Arthropod with Unique Anatomy #3047901 (License: Personal Use)

The horseshoe crab (Limulus polyphemus) features a tough, brownish exoskeleton divided into three sections: the prosoma (front shield), opisthosoma (abdomen), and a long, rigid telson used for flipping over. Its underside reveals five pairs of walking legs, some modified for feeding, and book gills for respiration. Despite its name, it is more closely related to spiders and scorpions than true crabs.

Used in educational biology content, marine conservation pages, or medical research sites highlighting鲎 blood’s use in endotoxin testing; matches user intent to learn about anatomy, evolution, or ecological significance.