Arthropods

4 innovations

New appendages
Prominent exoskeleton
Reduced coelom
Growth by moulting

New appendages

Join legs for the first time

Reduced coelom

Exoskeleton means no need for hydrostatic skeleton
Used only to surround gonads and excretory organ

Growth by molting

Shedding

1. Old cuticle separates from epidermis

2. New cuticle is secreted

3. Old cuticle splits and sheds

4. Cuticle hardens

Arthropod digestive system

Full set of modified mouthparts for very different feeding modes

Arthropod nervous system

Well developed
Large brain to coordinate movement
Many different chemo

Arthropod respiratory system

Hard cuticle reduces permeability so there is a need for gills, trachea, etc

Insect excretory system

Malpighian tubules

spider excretory system

Coxal glands

Crustaceans excretory system

Green glands

Classification of arthropoda

Triolobita
Chelicerata
Crustacea
Uniramia

Triolobita

Extinct
3 lobes

3 tagmata of trilobita

Cephalon
Trunk
Pygidium

Trilobita appendages

Antennae and biramous limbs

parts of a biramous appendage

Protopodite becomes endopodite and exopodite

Chelicerata tagmata

two tagmata: cephalothorax + abdomen

Chelicerata appendages

1 pair of chelicerae
1 pair of pedipalps
4 pairs of walking legs

3 classes of Chelicerata

Merostomata, Pycnogonida, Arachnida

Merostomata (horseshoe crabs)

Large carapace
Abdomen with a telson

Class Pycnogonida (sea spiders)

Elongated cephalothorax
Reduced abdomen
2 tagmata

Class Arachnida (spiders, mites, scorpions, ticks)

Prominent wax on cuticle

Spiders

Narrow waist
Nets for feeding, dispersion, hold eggs
Hunters and ambush predators

What do spiders use to produce silk and nets

Spinnerets

Scorpions

Terminal stinger
Tropical carnivore species
Some are lethal

Mites and ticks

Ectoparasites
No waist
Scavenger

Crustacea tagmata

cephalon, thorax, abdomen

Crustacea appendages

biramous
2 pairs of antennae
Mandibles + maxillae

Class Malacostraca

Includes decapods (crabs and shrimp)
5 pairs of legs
6 pairs abdominal

Crustacea reproduction

Dioecious
Eggs brooded