Arthropods

General Characteristics• All have jointed legs

• Evolved from annelids (segmented worms)

• All have an exoskeleton made of chitin

• All have bilateral symmetry

WOW BEHAVIOR!• All molt- shed skin to allow for growth (lobster

example)

• Spiders molt too

Body Arrangement• All have 3 body segments – head, thorax

and abdomen

Arthropods all have an open circulatory system

“Blood” is confined to vessels for only a small portion of it’s circuit through the body.

FIVE CLASSES

• Centipede – one pair of legs per segment

• Millipede- two pair of legs per segment

• Insects- 3 pair of legs per thorax

• Arachnids- 4 pair of legs per thorax

• Crustaceans-5 pair of legs per thorax

Centipedes

Legs• Centipedes have 1

pair of legs per body segment.

DefensesHave large

poisonous fangs on their first appendages.

Centipede• Name means 100 feet. Do

they have 100 feet?

Centipedes• Have longer

antennae than other animals in the same class.

• Antennae are sensory organs, used for touch and smell

Feeding • Usually are

carnivorous, eating other arthropods

• Eat snails, slugs, and worms

Millipedes

Millipedes• Millipedes have 2 pair

of legs per segment.• Body has many

segments; as many as 100

Millipedes• Generally not

poisonous to humans

MillipedesName means 1000 feet. Does it have 1000 feet?

Millipedes• Millipedes spit

cyanide acid at prey.

InsectsFar out!!

Insects have 3 pairs of legs on their thorax

INSECTS undergo metamorphosis• Complete metamorphosis:

– Egg– Larvae– Pupa– adult

INSECTS undergo metamorphosis• Incomplete metamorphosis:

– Egg– Nymph– adult

Insects have 3 simple eyes between two compound eyes

Insects breathe through holes in their sides (usually the thorax) called spiracles

Many insects have camouflage

More Camouflage

Insects mimic environment

Flight was an evolutionary advantage to insects• Damselfly goes from water to flight

Common blue damselfly

Drosophila flight

The miraculous honey bee!• Honey bees and relationship to humans

Wild and wonderful

Praying Mantis at the snake buffet

Weevil family

Amazing Mantis!!

Wild and wonderful

Monarch butterfly

Swallow tail species

Viceroy butterfly

Arachnids

Arachnid Includes

Spiders

Mites

scorpions

Arachnids have 4 pairs (8)of legs

All spiders have 2 pair of mouthparts

Spiders have fangs

Arachnids breathe by book lungs

Horseshoe Crabs are more closely related to arachnids then to crustaceans.

Malpigian tubules are used as kidneys to filter the “blood”

Arachnids produce a strong elastic silk from spinerettes to build a web to capture their prey

Cephalothorax Cephalothorax is the head attached to the thorax.

VisionOnly have simple eyes

Arachnids have poison to kill their prey

Brown Recluse

Arachnid feedingArachnids use enzymes

to dissolve food before ingestion.

Camel Spider

Trick photography

Real spider

Crustaceans

Crustacean• Crustaceans all

have a cephalothorax

• Examples are crayfish, shrimp, lobster, and crabs

Most are aquatic• EXCEPT – rolly polly (pill bugs)

LocomotionHave 5 pairs of

appendages

Crustaceans have a special appendage used for swimming called a swimmerets

Green GlandHave an organ called

the green gland: which regulates the amount of salt and water in the body

Carapace – hard outer shell – protects inner organs

Internal Anatomy

Amount of Legs• All crustaceans have five pair of appendages• And crustaceans have two pair of antennae

General Information• Crustaceans breathe

though gills• Mostly scavenge for

food

Some have a long appendage called a

telson-tail•