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 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 flea Pill bugs

Class CrustaceaMost 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 MerostomataRespire through book gills (much like book lungs in

arachnids).Have both simple and compound eyes.Only 4 species existSuperbly 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 regions Yes Yes Yes

4 pairs of legs Yes

5 pairs of legs Yes Yes

True gills Yes

Book lungs/book gills

Antennae

Chewing mouthparts

Yes; book lungs

No

Yes

Yes; book gills

Yes

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 mandiblesTwo 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 legsDo 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 herbivorousHead followed by 20 to 200 segments2 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 regionsThree pairs of walking legsThree pairs of walking legs located on thoraxOne 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 respirationHave compound eyesMost live on land.Many have complete metamorphosis