ARTHROPODSARTHROPODS

ArthropodsArthropods

(“jointed foot”)(“jointed foot”) ¾ of all animals on planet Earth! ¾ of all animals on planet Earth!

750,000+ species….why so numerous 750,000+ species….why so numerous and successful?and successful?

1: Reproduce fast & in large 1: Reproduce fast & in large numbersnumbers

opportunity for variation is therefore great opportunity for variation is therefore great take advantage of different food take advantage of different food

sources…pass through developmental sources…pass through developmental stages such as ‘larva’ and ‘adult’ in stages such as ‘larva’ and ‘adult’ in metamorphosismetamorphosis

#2: Exoskeleton (outside)#2: Exoskeleton (outside)

Changed the single fortress (shell) to a Changed the single fortress (shell) to a flexible suit of armorflexible suit of armor

Protection; barrier against loss of body Protection; barrier against loss of body fluids; must be recycled and shed fluids; must be recycled and shed (molted!) to make room for growth(molted!) to make room for growth

#3: Segmentation#3: Segmentation

More flexible movementMore flexible movement Creates lots of interior ridges for muscle Creates lots of interior ridges for muscle

attachments, going in different directionsattachments, going in different directions

#4: Striated Muscles#4: Striated Muscles

voluntary and quick contracting (but, they voluntary and quick contracting (but, they get tired quickly….need lots of oxygen to get tired quickly….need lots of oxygen to burn food for quick energy!burn food for quick energy!

#5: Efficient air moving #5: Efficient air moving systemssystems

Gills in water; book lungs for spiders; Gills in water; book lungs for spiders; tracheae (pipes) for insectstracheae (pipes) for insects

#6: jointed appendages#6: jointed appendages

modified for locomotion (legs, wings), modified for locomotion (legs, wings), eating (claws, mouthparts), sensing eating (claws, mouthparts), sensing (antennae)(antennae)

#7: Sense Organs#7: Sense Organs

eyes (simple or compound); hair on legs, eyes (simple or compound); hair on legs, body, antennae; chemical sensesbody, antennae; chemical senses

Arthropod Groups (taxa)

The arthropods are divided into two large groups that exist today:

Chelicerates

and

Mandibulates

Chelicerate Arthropod Characters:

Pincher-like mouthparts - chelicerae - and pedipalps

NO antennae

Two body regions, usually - cephalothorax & abdomen

Four pairs of legs

Horseshoe crabs and arachnids are only living groups

Orders of Arachnids

Scorpions

Pseudoscorpions

Daddy Long-Legs

Mites & Ticks

Spiders

Scorpion Tick(a mite)

Pseudoscorpion

Daddy-long-legs

WolfSpider

Scorpion Anatomy

chelicerae eyes pedipalp

Pseudoscorpion

pedipalps &chelicerae

cephalothorax

abdomen

Mite and Tick Body Regions

American dog tick male

Blacklegged (deer) tick female

American dog tick female laying egg mass (1000-2000 eggs!).

Clover mites

Twospotted spider mites

Predatory mite

daddy long-legs

cephalothorax abdomen

pedipalp

chelicera (fang)

cephalothorax

abdomen

narrow waist

Spider Anatomy

Abdomen

Pedipalp

Chelicera (fang)

Cephalothorax

Jumping Spider

Wolf spider with egg case Spitting spider

TarantulaOrb-weaving spider

Black widow with egg case

Brown recluse

Mandibulate Arthropod Characters:

Mouthparts are mandibles - normally chewing sideways

One or two pairs of antennae

Various body region arrangements - cephalothorax & abdomen / head & trunk / head, thorax & abdomen

Variable leg numbers

Insects, crustaceans & myriapods

Classes of Myriapods(many legged arthropods)

(all have one pair of antennae, a head region, and trunk with many pairs of legs, use trachea)

Diplopoda - millipedes

Chilopoda - centipedes

Myriapods

Millipede (Diplopoda)

Two pair of legs per visible segment, attached under body.

Centipede (Chilopoda)

Pair of fangs under head, one pair legs per visible segment - attached to side of body.

No fangs, no eyes, legs attached to side of body.

[one pair of antennae, head & trunk regions, trunk with many pairs of legs]

Millipede (Diplopoda)

Centipede (Chilopoda)

Garden centipede

Insecta ClassInsecta Class

3 segments 3 segments head, thorax, abdomen head, thorax, abdomen 1 pair of antennae1 pair of antennae Special characteristics:Special characteristics:

WingsWings PheromonesPheromones MetamorphosisMetamorphosis

PhereomonesPhereomones

Chemical signalsChemical signals Used forUsed for

Marking trailsMarking trails Identification of organismsIdentification of organisms Signaling troubleSignaling trouble Signaling sexual readinessSignaling sexual readiness

Metamorphosis Metamorphosis

IncompleteIncomplete Born as a smaller version of the adultBorn as a smaller version of the adult 3 stages3 stages Egg Egg nymph nymph adult adult Nymph molts many times into different Nymph molts many times into different

“stage” of nymph“stage” of nymph

MetamorphosisMetamorphosis

CompleteComplete Born as a complete different version than Born as a complete different version than

adultadult 88% of metamorphosis88% of metamorphosis 4 stages4 stages Egg Egg larva larva pupa pupa adult adult

Classes of Crustacea• mostly marine, fresh water, a few terrestrial• all have two pair of antennae• five or more pairs of legs• segmented abdominal appendages• head & trunk or cephalothorax & abdomen body arrangement• have gills

Sowbugs or pillbugs

Sand fleas

Barnacles

Crabs, lobster, shrimp

Crayfish cephalothorax(Decapoda)

Sowbug (Isopoda), a terrestrial crustacean