Although the horseshoe crab resembles a crab it is actually more related to scorpions and spiders. However most people are unaware of the similarities between the spider and the horseshoe crab. The pictures below break down the anatomy for you.
The body of the horseshoe crab is made up of three parts.
The Prosoma or head and thorax of the crab (front section)
The Opisthosoma or the abdomen of the horseshoe crab (middle section)
And finally the Telson or the tail
The horseshoe crab has a hard Exoskeleton much like a crab. Actually it wears it’s skeleton on the outside. The horseshoe crab must shed this shell in order to grow and this shell is then called a molt. They do this by absorbing water through their gills, making themselves larger which splits the shell so they can crawl out of it.
The horseshoe crab has two large compound eyes located on the top of the prosoma. These eyes are very large and contain hundreds of lenses as compared to human eyes which only have one lens. So they see very differently than we do.
They also have simple eyes scattered all over it’s body, even on the tail. These eyes are merely photo sensitive areas which they use to find food and detect predators.
Horseshoe Crabs have 5 sets of leg like appendages that are used for mobility and to direct food into it’s mouth. The horseshoe crab doesn’t have a jaw. What it does is direct food into it’s mouth where the food is ground up by it’s gizzard which contains sand and small bits of gravel to help with the process.