“jointed foot”Insects, centipedes, millipedes,

spiders, and crustaceans

Most extensive phylaProportion of all described species on earth

Insects 56.3%Arthropods Spiders 4.5% 65%

Crustaceans 2.4%Others 1.2%Mollusks 4.2%

Other invertebrates Nematodes 0.9% 6.1%Others 4.0%

Vertebrates 2.7%Flowering plants 14.3%Fungi 4.2%Algae 2.4%Protozoans 2.4%Bacteria & viruses 0.5%

Population density

• 1x1019 individuals (insect)– = 10 quintillion individuals– =10 million million million

Arthropod Diversity

• 1,004,898 described species as of 2009 – (Footit & Adler)

• True estimates most likely 5 million species (Erwin 1982)– 1 million described– 4 million undescribed

Why have arthropods achieved such great diversity and abundance?

• Small size– Less energy requirement– Habitats/ niches

• Flight (some individuals)– Escape/dispersal

• Cuticle– Protective/ efficient attachment for muscles – (more muscle mass per unit body mass)

• Highly organized/ effective sensory neuro-motor system– Recognize integrate and respond to external and internal signals

• High reproductive capacity• Differentiated stages

– Larva vs adult

General Characteristics• Jointed legs• Eucoelomate• Protostome• Exoskeleton

– Chitin• Feeding

– Carnivorous– Herbivorous– Omnivorous

• Habitat– Air– Land– Freshwater– Marine – Parasitic (endo and exo)

• Size– >0.1mm to 4 m

Tagma- groups of fused segments

2 Tagma• Cephalothorax

• Opistosoma

Tagma- groups of fused segments

3 Tagma• Head

• Thorax

• Abdomen

Phylum Arthropoda

• Subphylum Chelicerata– Class Merostomata– Class Arachnida

• Subphylum Crustacea• Subphylum Uniramia– Class Chilopoda– Class Diploda– Class Insecta

Subphylum Chelicerata• 6 pairs of cephalothoracic appendages– Chelicerae (1 pair)– Pedipalps (1 pair)– Walking legs (4 pair)

• No antenna• Two classes– Class Merostomata• Horseshoe crab

– Class Arachnida• Spiders, scorpions, ticks and mites

Mandibulates

• Characteristics• Mouthparts are mandibles• One or two pairs of antennae• 3 tagma– Head– Thorax– Abdomen

• Variable leg numbers• Insects, crustaceans, and myriapods

Class Merostomata

Class Arachnida

• Spiders• Scorpions• Whip scorpions• Ticks• Mites• Harvestmen

Araneae: Spiders• Respiration– Book lungs • Parallel air pockets extending into a blood filled chamber

– Trachea• Air tubes connecting the outside directly to the blood

• Excretion– Malphighian tubules– Uric acid

• Sensory– Simple (poor vision movement not shapes)– Cuticular mechanoreceptors (sense vibrations/ air

movements)• Sensory setae• Trichobothria• Slit sense organs

• Web spinning– Spinnerets/ silk glands– Scleroprotein (liquid but hardens as a result of being

pulled)– Strong and stretchy• Stronger than steel but will stretch 1/5 their length before

breaking

• Reproduction– Male spins web to drop sperm in, gathers it with

his pedipalps and carries it to the females genital opening (lock and key)

– Female lays eggs in a net (cocoon), she may carry it or attach it to a plant

• Venom– Largely harmless to people (2 exceptions)

• Black widdow Latrodectus dectes– 4 to 5 out of 1000 bites are fatal

• Brown Recluse Loxosceles skelos– 0 proven fatalities , most bite heal on their own, 10% cause tissue

damage warranting medical attention.

– Neurotoxin• Disrupt nerve impulses

– Hemalytic toxin• Destroys blood cells and linings of capillaries

Mandibulates

• 2 groups– Subphylum Crustacea– Subphylum Uniramia

Subphylum Crustacea• Characteristics– Marine, fresh water and terrestrial– Two pair of antennae– Five or more pairs of legs– Biramious (two main branches)– Gills

Internal Features• Hemocoel– Blood-filled body space

• Muscular system– Antagonistic arrangement• Extensors- draw parts away from the body• Flexors- draw parts towards the body

• Circulatory System– Open circulatory system• No veins• No separation of blood from intestinal fluid

– Blood leaves the heart by way of the arteries, circulates through the hemocoel, and returns to venous sinuses or spaces before it reenters the heart

• Respiratory system– Small• Gas exchange occurs over thin areas of the cuticle or

the entire body– Large• Feather like gills

• Excretory system– No malpighian tubules– “green glands”• Pair of tubular structures located in the ventral part of

their head next to the esophagus– Excretion of nitrogenous wastes (ammonia) takes

place across the cuticle

• Nervous system– Fused ganglia (brain-ish)• Supraesophageal ganglia

– Eyes and antennae• Subesophageal ganglia

– Mouth and appendages

– 2 ventral nerve chords• Sensory system– Eyes• Compound (ommatidia)

– Tactile hairs

• Reproduction– Dioecious– Parthenogenic• Female lays unfertilized eggs which develop into young

– Metamorphosis• Ecdyis – Shedding of the cuticle– Controlled by hormomes and external conditions

Classes• Class Remipedia• Class Cephalocarida• Class Branchiopoda• Class Ostracoda• Class Maxillopoda• Class Malacostraca– Sowbugs- pillbugs– Sand fleas– Barnacles– Crabs, lobster, shrimp

Subphylum Uniramia

• 2 groups– Insects– Myriapods (centipedes and millipedes)• Many foot

• Mostly terrestrial – Very few aquatic (freshwater)

• One pair of antennae• Appendages uniramous (one)

• Many legged arthropods• All have one pair of antennae• Use trachea• Classes– Diploda• Millipedes

– Chilopoda• centipedes

Myriapods

Class Chilopoda

• Centipedes – Flattened bodies– 1 pair of legs per metamere (segment)– 1 spiracle per metamere– 15-177 segments– Poisonous– Viviparious – (live birth)– Carnivorous

• Cockroaches & other insects• Earthworms

Class Diploda

• Millipedes– 2 pairs of legs per metamere– 2 spiracles per metamere– 25-100 segments– Harmless – Herbivorous– Repugnatorial glands

Class Insecta

• 3 pairs of legs• 3 tagma– Head– Thorax– Abdomen

• Distribution– Every continent except Antarctica

• High level of adaptability and specificity

External Anatomy• Sclerites- system of plates which comprise the

exoskeleton

Movement

• Walking– Triangle legs/ tripod gait

• Flight– Only invertebrates that can fly– Wings composed of cuticle– Most have 2 pair– Flies 1 pair + halteres– Direct flight muscles

• Attach to the wing– Indirect flight muscles

• Attach to the cuticle

Nutrition• Digestive system– Foregut• Mouth- gizzard (proventriculus)• Cuticle lined

– Midgut• Stomach and gastric ceca

– Hindgut • Intestine-anus• Cuticle lined

Feeding

• Phytophagous/ herbivorous– Feeding on plants

• Saprophagous– Feeding on dead animals

• Detrivorous – Feeding on dead material

• Predaceous• Parasitic– Hyperparasitism– Parasitoids

Circulation

• Open circulatory system• Hemolymph (blood)• Tubular heart• Limited oxygen transport

Gas exchange

• Tracheal system– Extensive network of thin-walled tubes that

branch to every part of the body

Reproduction• Dioecious • Strategies– Viviparious

• Live birth– Parthenogenic

• Growth and development of young without fertilization– Oviparious

• Young develop from eggs laid outside the body– Ovoviparious

• Young develop from eggs held within the female

Metamorphosis

• 3 types• Holometabolous “complete”– Egg, larvae, pupae, adult

• Hemimetabolous “incomplete”– Egg, nymph, adult

• Ametabolous “no”– Direct development

Nervous system• Sense organs– Keen sense perception– Mechanoreception

• Sensilla– Auditory reception

• Setae/sensilla• Tympanic membrane

– Chemoreception(taste or smell)• Mouthparts

– Vision• 2 types of eyes

– Simple (ocelli)– Compound (made of ommatidia)

Defense

• Mimicry– Imitation of a noxious/dangerous species by

coloration• Crypsis– Camouflage

• Chemical defense

Insects and human welfare

• Negative– Crop damage and loss

• 75% loss pre pesticide– Disease

• Malaria- kills 1.2 million people annually

• Positive– Predaceous insects– Food production

• Pollination• Efficient protein source

INSECT ORDERS

Ephemeroptera

• Mayflies

Odonata

• Dragonfly– “Tooth wing”

Orthoptera

• grasshoppers/ crickets– “straight wing”

Dermaptera

• Earwigs– “skin wing”

Plecoptera

• Stonefly– “Twist wing”

Isoptera

• Termites – “equal wing”

Hemiptera

• True bugs– “Half wing”

Neuroptera

• Lacewings– “nerve wing”

Coleoptera

• Beetles– Sheath wing

Lepidoptera

• Butterflies – Scale wing

Diptera

• Fly– Two wings

Blattodea (roaches)

Latin “blatta” = cockroachSpot ID• Flat• Spiny legs• Long antennae