Arthropoda · arthropods

Atlantic horseshoe crab

Limulus polyphemus

Limulidae · horseshoe crabsIUCN: Vulnerable

An ancient arthropod more closely related to spiders than crabs.

Fun factIts blue, copper-based blood is used to test vaccines and medical devices for bacterial toxins.

Classification

Arthropoda › Xiphosura › Limulidae

Kingdom Animalia animals
- Many-celled organisms that eat other living things for energy (heterotrophs)
- Cells have no cell walls
- Most can move at some stage of life
Clade Bilateria bilateral animals
- Body has a left and right side that mirror each other (bilateral symmetry)
- Head end with concentrated nerves; three tissue layers
- Includes about 99% of all living animal species
Clade Protostomia protostomes
- In the embryo, the first opening usually becomes the mouth
- Main nerve cord runs along the belly (ventral)
- Includes mollusks, worms, and arthropods
Clade Ecdysozoa molting animals
- Grow by shedding their outer layer (molting, ecdysis)
- No cilia used for movement
- Includes arthropods and nematode worms
Phylum Arthropoda arthropods
- Hard outer skeleton made of chitin (exoskeleton)
- Jointed legs and a segmented body
- The largest animal phylum by species count
Subphylum Chelicerata chelicerates
- First pair of appendages are pincers or fangs (chelicerae)
- No antennae
- Includes horseshoe crabs, sea spiders, and spiders
Order Xiphosura horseshoe crabs
- Horseshoe crabs: horseshoe-shaped shell (carapace) and spike-like tail (telson)
- Ancient group with blue, copper-based blood
Family Limulidae horseshoe crabs
- Horseshoe crabs come ashore in great numbers to spawn on beaches
Genus Limulus
- Species in the same genus are very close relatives and often look alike.
Species Limulus polyphemus Atlantic horseshoe crab