Phylum Arthropoda

Phylum Arthropoda General Characteristics

General Characteristics • Largest phylum in the animal kingdom • Includes insects, spiders, millipedes, centipedes, crabs and krill. • Are bilaterally symmetrical; coelomate; protostomate. • Exoskeleton. Major component: the polysaccharide, chitin. • Jointed appendages. • Well-developed sense organs • Open circulatory systems • Group is important as pollinators of flowers, carries of disease, and as food. • About 1+ million species known at present.

Class Arachnida • Includes ticks, mites, scorpions and spiders Black-legged deer tick Striped bark scorpion Acarina Wolf spider

Class Arachnida • Two body regions: cephalothorax and abodomen. • Have 4 pairs legs attached to their thorax. • A pair of chelicerae (fangs). • A pair of palps. Function as sense receptors, short arms, and pincers (in scorpions).

Class Arachnida • All arachnids are carnivores. Most eat insects. • No antennae. • Many have 8 simple eyes. • Respire through book lungs and tracheae. • About 57,000 species, including Latrodectusmactans (black widow spider) and Dermacentorvariablis (wood tick).

Class Crustacea • Includes crabs, shrimps, water fleas, and pill bugs. Brown shrimp Blue-clawed crab Water flea Pill bugs

Class Crustacea • Most are marine, but some live in fresh water, and a few live on land. • 2 main body regions in most. • 5 pairs of legs (4 pairs for walking and 1 pair for grasping (chelipeds)).

Class Crustacea • 5 pairs of head appendages, including 2 pairs of antennae and chewing mouthparts, which are useful in classifying them.

Class Crustacea • Respiration by gills (most are aquatic). • Many have compound eyes. • About 35,000 species, including Callinectessapidus(blue crab) and Homarusamericanus (American lobster).

Class Merostomata • Horseshoe crabs. All are marine. • 2 main body regions. • Easily recognized by horseshoe-shaped carapace and long telson. • 5 pairs of legs (like crustaceans). • No antennae (like arachnids).

Class Merostomata • Respire through book gills (much like book lungs in arachnids). • Have both simple and compound eyes. • Only 4 species exist • Superbly adapted to their environment from early in the history of life on Earth, they have changed little. • Chesapeake Bay hosts largest population in the world.

Class Chilopoda • Two body regions (cephalothorax and abdomen). • Have a head with one pair of long antennae and a pair of mandibles • Two pairs of maxilla (appendages which hold their captured food and aid in chewing with side to side movement).

Class Chilopoda: Centipedes • Carnivorous. • Head followed by 15 to 177 body segments. • First body segment has a pair of poisonous claws. • All other segments have 1 pair of jointed legs • Do not have 100 legs (as their common name suggests). • Tracheae used for respiration. Vietnamese Centipede

Class Diplopoda: Millipedes • Three body regions (head, thorax, and abdomen). • Have a head with one pair of antennae and a pair of mandibles • One pair of maxilla

Class Diplopoda: Millipedes • Mostly herbivorous • Head followed by 20 to 200 segments • 2 pairs of jointed legs on each segment. • Do no have 1,000 legs (as their common name suggests). • Tracheae used for respiration.

Class Insecta • Single largest class of organisms; more than 750,000 known species. • Includes bees, flies, grasshoppers, lice, butterflies, moths, and beetles (450,000 species).

Class Insecta • Three body regions • Three pairs of walking legs • Three pairs of walking legs located on thorax • One pair of antennae on head.

Class Insecta • Have complex mouth parts with one pair of maxilla and mandibles. • When wings are present, have one or two pairs of wings on thorax. Two pairs on Dragonfly Mosquito has one pair of wings

Class Insecta • Only group of invertebrates capable of flight. • Tracheae used for respiration • Have compound eyes • Most live on land. • Many have complete metamorphosis

Phylum Arthropoda