Chapter 24

Arthropods

1

Arthropod Humor

2

Animal Groups

3

Arthropod Ancestors

Like annelids

True coelom

Segmented body

Fossils among the oldest and best

Ex: Trilobites

600 million years

Extinct

Once common in seas

Jointed appendages

Complex eyes 4

The Arthropods

5

Arthropod Numbers

More than all other animals combined

> 1 million species

More kinds of beetles alone than there are vertebrates

Most small ~ 1mm (.003 in)

Some 3.6 m (about 12 ft)

Ex: spider crabs

6

Arthropod Characteristics

1) Jointed appendages

2) Segmentation

3) Distinct head

4) Exoskeleton

5) Many have wings

6) Open circulatory system

7) Malpighian tubules for

excretion

8) Respiration

Gills

Book lungs

Tracheae

7

1) Jointed Appendages

Appendage - Structure

that extends from the body

Used for:

Walking

Swimming

Sensing

Manipulating food

Chewing

Include:

Legs

Antennae

Mouth parts

8

Jointed Appendages

Bend

Can have 6 to 100s

Shaped like:

Rakes

Tweezers

Nutcrackers

Hammers

Paddles

9

Segmentation

Often exists only in larval stage

Segments fuse during development

Most have three distinct body regions

Head

Thorax (mid body region)

Abdomen

Some have cephalothorax = head and thorax fused

ex: crab p. 690

10

Distinct Head

Sometimes attached

to thorax forming the

cephalothorax

Contains:

Eyes

Brain

Antennae

11

Compound Eyes

Thousands of individual

units

Each has lens and

retina

Brain receives info from

each

Makes unclear image

See motion very quickly

Most arthropods have

12

Simple Eyes

Single lenses

Do not form images

Distinguish light and dark

Some arthropods only

have simple

Most have both simple and

compound

Ex: dragonflies’ and

locusts’ simple eyes

detect horizon

Help stabilize position in

flight 13

Exoskeleton

Skeleton on outside

Protection and muscle

attachment

Composed mostly of chitin

Linked sugars

Layered

Nonliving - cannot grow!

Tough but brittle

Thickness varies b/w groups

Thinner at joints = flexible

14

Molting = ecdysis

Shedding of exoskeleton

Controlled by hormones

New skeleton forms below

old

Larger than old

Old gets broken down by

enzymes and breaks open

Animal crawls out

Every surface is shed

Sometimes animal dies in

process

New is soft, but hardens

Arthropod molting 1.37.mp4 15

Respiration

In Terrestrial arthropods:

Tracheae

Fine network of tubes

Carry oxygen Valves control

Spiracles Openings in abdomen where

air enters

Spiders use book lungs

Leaf-like plates

Large surface area

Lobsters have gills – large surface area

16

Arthropod Respiratory System

17

6) Excretion

Terrestrial arthropods

Unique

Malpighian tubules

Finger-like structures

Attached to gut

Bathed in blood

Conserve water

Eliminate metabolic

wastes

18

Classification of Arthropods

Domain Eukarya

Eukaryotic cells

Kingdom Animalia

Multicellular

Heterotrophic

No cell wall

Phylum Arthropoda

Arthro = “Jointed”

Poda = “Feet/Appendages”

19

Two Basic Groups of Arthropods

1) Arthropods with jaws

Subphylum Uniramia (yoo nuh RAY mee uh)

Subphylum Crustacea

2) Arthropods with

fangs/pincers

Subphylum Chelicerata (kuh

LIS uh rahd a)

20

Subphylum Chelicerata

Two minor classes

Horseshoe crabs

Sea spiders

21

Subphylum Chelicerata

Largest class =

Arachnida

Mouthparts called

chelicerae (kuh LIS uh

ree) - modified into

fangs/pincers

22

Class Arachnida

Spiders

Scorpions

Ticks

Mites

Daddy longlegs

23

Arachnida Characteristics

No antennae

Appendages

Chelicerae – 1 pair

Pedipalps – 1 pair

Walking legs – 4 pair

Two body regions

Cephalothorax

Abdomen

Joined by pedicel

24

My Goodness! So Many Eyes!

Most have 8 eyes

Arrangement varies

Identification

Vision varies

Hunters

Better vision

Web builders

Poor vision

25

My Goodness! Such Hairy Legs!

Hearing

Vibrations detected

by “Hairs”

Taste and smell

Organs on legs and

pedipalps

26

Spider Feeding

Important predators

Poison glands

Secrete toxin

through fangs

Kills or paralyzes

Injects enzymes

Digests tissues

Liquifies

Suck up food

27

Morphology of a Spider

28

Internal Anatomy of a Spider Page 695

29

Internal Anatomy of a Spider

30

Book Lungs - Respiration

Contain sheets of thin

plates

Blood filled

Air passes over them

Blood picks up oxygen

by diffusion

31

Webs and Spiders

All spiders can make

silk

Use spinnerets to

release

32

Dangerous Spiders – Brown Recluse

Called “fiddleback” or

“violin”

Violin-shaped marking on

top of cephalothorax

Six eyes

All arranged in pairs

33

Dangerous Spiders – Brown Recluse

Found in Midwest and Southern U.S.

Under rocks, logs, woodpiles, dirt, or debris

During cooler months, can find in house

Basements

Attics

Vents

34

Dangerous Spiders – Brown Recluse

Bite often not felt

Reaction depends:

Amount of venom injected

Victim’s body reaction to

venom

Wound

Deep

Sore

Long time to heal

35

Dangerous: Black Widow Spider

Many species in U. S.

Potent neurotoxic venom

Most venomous spider in N.

America

Female injects

Small dose

Rarely causes death

Human mortality < 1%

Usually found outside

Every state except Alaska

36

Black Widow Spider

Adult female = shiny and jet

black

Red hourglass marking on

bottom of abdomen

~ ½ inch long not including

the legs

Adult males = harmless

~1/2 female’s size

Black widow vs. Brown Recluse

3:19

37

Other Arachnids - Scorpions

Scorpions

Long slender abdomen

End of abdomen = venomous

stinger

Folded over body

Pedipalps = large pincers

Hold food

Reproduction

38

Other Arachnids

Most = small

Ex: mites, chiggers, and

ticks

Head, thorax, and

abdomen are all fused

Distributed throughout

world

39

Mites

Most not harmful

Some plant/animal pests

Some spread infections

Ex: Lyme disease spread by

deer ticks Symptoms include:

Fever

Headache

Fatigue

Characteristic “bulls-eye” skin

rash

Can be treated w/ antibiotics

40

Mites

Dust mites

Major cause of

allergies

Eye lash mites

41

Subphylum Uniramia

Class Insecta Kingdom Animalia

Phylum Arthropoda

Subphylum Uniramia

Mandibles

Class Insecta Life of Insects - Attenborough_ Life

in the Undergrowth 8 min

42

Insects by the Numbers:

Largest group of

organisms on Earth!

Mostly terrestrial

> 700,000 named

species

~80% of known

animals

New species

discovered every

day!

43

Insect Body Plan

Three body regions:

Head

Thorax

Abdomen

One pair of antennae

Three pairs of legs

Most have 2 pairs of

wings

44

Insect Structure – The Head

1 pair of compound

eyes

Some have simple

eyes

1 pair of antennae

Mandibles or modified

mouth parts

45

Insect Mouth Parts

Modified for different types of feeding

Piercing

Lapping

Sucking (proboscis)

Chewing

46

Grasshopper Mouth Parts

47

Antennae Structure &

Modification

Sensory structures for:

Touch

Smell

48

Insect Thorax

Three segments:

1st = (prothorax)

Middle = (mesothorax)

Last = (metathorax)

All have 1 set of legs

Wings may be present

Middle and last segment

Spiracles

Openings where air enters

On the middle and last segments

49

Wing Structure & Modification

Most 2 pairs of wings on thorax

Some have one or no pairs

50

Leg Structure & Modifications

51

Insect Abdomen

Spiracles on each segment

Tympanum

Membrane

Hearing organ

Some insects

Female abdomen

Ovipositor

Deposits eggs

52

Grasshopper External Structure

53

Grasshopper External Structure

54

External and Internal Structure

55

Grasshopper Internal Structure

56

Insect Life Cycle

Complex

Metamorphosis = “to

change”

Dramatic

Two types:

Complete

Incomplete

57

Complete Metamorphosis

Most ~ 88%

Four stages

1) Egg

First stage

2) Larva

Eating machines

Different foods than adults

Do not look like adult

Ex:

Caterpillars

Maggots

Grubs

3) Pupa

Do not eat

4) Adult 58

Incomplete Metamorphosis

~ 12%

Three stages:

1) Egg

First stage

2) Nymph

Look like small adults

No wings

Cannot reproduce

Eat same food as

adults

3) Adult 59

Insect Orders - Coleoptera

= “Sheath” “Wing”

Beetles

Chewing mouth parts

2 pairs of wings

First pair hardened into elytra

Protective

No veins

Second pair

Membranous

For flying

Complete metamorphosis

60

Coleoptera Life Cycle

Complete metamorphosis

Egg

Larva

Pupa

Adult

61

Insect Orders - Coleoptera

62

Insect Orders - Lepidoptera

= “Scale” “Wing”

Butterflies

Moths

Sucking mouth parts

2 pairs of wings

Covered with scales

Complete metamorphosis

63

Insect Orders - Lepidoptera

Complete

metamorposis

Egg

Larva

Pupa

Adult

64

Parts of a Caterpillar

65

Insect Orders - Lepidoptera

66

Insect Orders - Diptera

= “Two” “Wings”

Flies

Mosquitoes

Only 1 pair of wings

Wings for flight

Halteres

Club-like structure

Behind wings

For balancing

Complete metamorphosis

67

Insect Orders - Diptera

Complete metamorphosis

Egg

Larva

Pupa

Adult

68

Insect Orders - Diptera

69

Insect Orders - Hymenoptera

= “Membrane” “wing”

Bees

Wasps

Ants

Two pairs of wings

Abdomen w/ narrow waist

Only insects with “stingers”

Social insects

Complete metamorphosis

70

Insect Orders - Hymenoptera

Complete metamorphosis

71

Insect Orders - Hymenoptera

72

Insect Orders - Odonata

= “Tooth” Dragonflies

Damselflies

Large compound eyes

Antennae short; bristle-like

Two part wings

Incomplete metamorphosis Aquatic immatures

Naiads

73

Insect Orders – Odonata

Dragonflies Damselflies

Strong flying insects Weak flying insects

At rest – wings out from body Most hold wings along

length of abdomen

74

Insect Orders - Odonata

Incomplete metamorphosis

Egg

Nymph

Adult

75

Insect Orders - Odonata

76

Insect Orders - Homoptera

= “Same” “Wing”

Cicada

Aphids

Leafhopper

Treehopper

Wings (if present) fold over back

Piercing and sucking mouth parts

Beak at base of head

Incomplete metamorphosis

77

Insect Orders - Homoptera

78

Insect Orders - Hemiptera

= "Heteroptera"

“Half” “Wing”

True Bugs

Forewings both

membranous and hard

portions

Piercing and sucking mouth

parts

Beak at front of head

Incomplete metamorphosis 79

Insect Orders - Hemiptera

Incomplete metamorphosis

Egg

Nymph

Adult

80

Insect Orders - Hemiptera

81

Insect Orders - Orthoptera

= “Straight” “Wing”

Grasshoppers

Crickets

Walking sticks

Mantids

Roaches

Chewing mouth parts

Leathery front wings

Hind wings fold like fan

Incomplete metamorphosis

82

Insect Orders - Orthoptera

83

Ephemeroptera

= “Wing for a day”

Mayflies

Adult stage of life cycle

is short

Few hours to days

Swarms

84

Insect Diversity

85

Insect Flight

May have been first

animals to have wings

Reach new food

Escape predators

Wings on thorax

Composed of chitin

Strengthened by veins

Most fold at rest

86

Insect Wings

Most = 2 pairs

One for flight and

other for protection

Diptera = 1 pair

Fleas and lice =

none

Halteres

Stability in flight

87

Social Insects

Live in colonies

Division of labor

Different individuals = different roles

Caste Role etermined by

Heredity

Diet

Pheromones

Examples Order Hymenoptera

Ants

Bees

Wasps

Isoptera Termites

Social Insect Video Clip

88

Insect Humor

89

Subphylum Uniramia

Mandibles

Unbranched appendages

One pair antennae

Major groups

Insects

Centipedes

Millipedes

90

Centipedes - Class Chilopoda

One pair of legs per segment

Predators

Eat arthropods (mostly)

Pair of poison claws

Paralyze prey

Jaws are weak

Rarely penetrate human skin

Centipede vs. Mouse Video

clip

91

Millipedes - Class Diplopoda

Two pairs of legs per segment

Eat plant material

Coil up when disturbed

Defense:

Secrete stinky juice from pores along sides

92

Millipede and Centipede

Comparison

93

Myriapoda Humor

94

Crustaceans

95

Subphylum Crustacea

Domain Eukarya

Kingdom Animalia

Phylum Arthropoda

Subphylum Crustacea

Examples:

Crabs

Krill

Pill bugs

Shrimp

96

Crustaceans

“Insects of the sea”

Most abundant in

oceans

Nauplius

Distinctive larval

form

3 pairs of branched

appendages

Molts

97

Aquatic Crustaceans

Food source for humans

Key part of food chains

Part of plankton

Many small

Ex:

Daphnia

Copepods

Ostracods

Fairy shrimp

Krill

98

Krill - Euphausia superba

Shrimp-like

In all oceans

Zooplankton

Feed on phytoplankton

Swarm in large groups

Food for:

Baleen whales

Manta rays

Whale sharks

99

Daphnia

100

Decapods

Larger

Ex:

Shrimp

Lobster

Crabs

Crayfish

Five pair of legs

1/4 of crustaceans

Cephalothorax

Carapace

Protective shield 101

Crayfish Appendages

Chelipeds

Anterior pair of legs

Large pincers

Defense

Swimmerets

Abdomen

Small, leg-like

Swimming and

reproduction

102

Crayfish Appendages

Uropods

Flattened

Paddle-like

Side of tail

Telson

“Tail spine”

Tip of tail

Movement

See p. 690

103

Crayfish Anatomy

104

Decapod Humor

105

Sessile Crustaceans

Hard plates open and close

Extend jointed, feathery

legs

Comb food from water

Hermaphrodites

Ex: Barnacles

Sessile as adults

Live on rocks, whales,

posts

106

Terrestrial Crustaceans - Order Isopoda

Only few

Pill bugs and Sow bugs

“Rolly-pollies”

“Wood lice”

Live in leaf litter

107

Isopod Features

3 body parts

1 prominent pair of antennae

7 pairs of legs

7 segments on thorax

Uropods on abdomen

Dark gray to white color

w/ or w/out pattern

108

109

Arthropods and Humans

Cause millions of $

of damage to crops

Use insecticides to

kill

Sometimes toxic to

other lifeforms

Sometimes don’t

break down;

accumulate =

biomagnification

110

New Pest Controls

Arthropod specific

neurotoxins

Insect traps and

physical barriers

Predators

Parasitic wasps,

ladybugs

GM plants

111

Spreading Human Disease

Bubonic plague

Bacterium carried by the flea

Yellow fever

Virus carried by mosquitoes

Malaria

Protozoan carried by

mosquitoes

West Nile virus

Virus carried by mosquitoes

Lyme Disease

Bacterium spread by deer tick

112