Subphylum Trilobita Subphylum Chelicerata Phylum Arthropoda Subphylum Trilobita Subphylum Chelicerata

Taxonomy Phylum Arthropoda Subphylum Trilobita (Extinct) Subphylum Chelicerata Class Merostomata (Horseshoe Crabs) Class Arachnida (Spiders, scorpions, and mites) Class Pycnogonida (Sea Spiders) Subphylum Crustacea Subphylum Uniramia Class Chilopoda Class Diplopoda Class Insecta

General Characteristics Arthropods have an exoskeleton made up of chitin- a polysaccharide attached to protein. Arthropods (‘joint foot’) have jointed appendages. Body is constructed of serially repeated segments (metamerism) Tagmatization- fusion and specialization of segments.

General Characteristics Triploblastic Eucoelomate Bilaterally symmetrical. Open circulatory system with blood-like tissue called hemolymph. Arthropods must molt, or shed their exoskeleton, in order to grow in size.

Subphylum Trilobita Trilobites are an extinct group of arthropods that dominated the oceans before the Mesozoic era. Body composed of three tagmata- head, thorax, and abdomen Biramous, or two-branched, appendages. All marine.

Subphylum Chelicerata Groups include the horseshoe crabs, sea spiders, spiders, scorpions, mites, ticks, and others. Unlike other arthropods, chelicerates do not have mandibles used for chewing food. Their first pair of appendages (chelicerae) are modified for tearing food apart) Two tagmata- cephalothorax, and abdomen. No antennae.

Class Merostomata Horseshoe crabs Living fossils. Horseshoe crabs have changed little in 425 million years! All marine

Class Merostomata

Class Pycnogonida Sea Spiders Predatory marine chelicerates. Sea spiders have almost no abdomen. The intestines of sea spiders have long diverticula that extend into the legs. Sea spiders have a long proboscis with a terminal mouth. They feed largely on cnidarians and other soft-bodied invertebrates.

Class Pycnogonida

Class Pycnogonida

Class Arachnida Generally terrestrial with a few aquatic types. Arachnids possess one pair of chelicerae, one pair of pedipalps, and four pair of legs. Two tagmata- cephalothorax and abdomen. Class Arachnida is composed of spiders, scorpions, solfugids, mites, ticks, and their kin.

Class Arachnida http://tolweb.org/tree?group=Arachnida&contgroup=Arthropoda

Spider External Anatomy

Spider Legs http://www.uky.edu/Agriculture/CritterFiles/casefile/spiders/anatomy/leg.png

Spider Internal Anatomy

Spinnerets http://www.dianamarques.com/images/spinnerets.jpg http://www.pbrc.hawaii.edu/bemf/microangela/mspigot7o.jpg

Silk Spiders have six spinnerets that can produce up to seven different types of silk. Spider silk is made of protein and is one of the strongest natural substances in the world.

Silk Silk is produced in liquid form, but dries upon contact with air. All spiders produce silk, but not all spiders spin webs. Silk is also used for shelter, reproduction, and drag lines for jumping and “ballooning.”

Black Widow Spider (Female)

Brown Recluse Spider

Tick Mite

Scorpion

Solfugid (A. K. A. Sun Spider, A. K. A. Camel Spider, A. K. A Solfugid (A.K.A. Sun Spider, A.K.A. Camel Spider, A.K.A. Wind Scorpion)

Pseudoscorpion