Phylum Arthropoda 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 Acarina – Dust mite Striped bark scorpion Wolf spider

Class Arachnida  Two body regions: cephalothorax and abdomen.  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 Latrodectus mactans (black widow spider) and Dermacentor variablis (wood tick).

Class Crustacea  Includes crabs, shrimps, water fleas, and pill bugs. Blue-clawed crab Brown shrimp Water fleaPill 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 Callinectes sapidus (blue crab) and Homarus americanus (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.

Arachnida (spiders) Crustacea (lobster) Merostomata (horseshoe crab) 2 main body regionsYes 4 pairs of legsYes 5 pairs of legsYes True gillsYes Book lungs/book gills Antennae Chewing mouthparts Yes; book lungs No Yes Yes; book gills Yes Yes; book gills No Yes

Dust Mites vs. Bed Bugs Class Arachnida Class Insecta Why???

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