Invertebrates

1
Chapter 33

• Invertebrates

2
LE 33-2
Cnidaria
Chordata
Echinodermata
Porifera
Other bilaterians (including Nematoda,
Arthropoda, Mollusca, and Annelida)
Deuterostomia
Bilateria
Eumetazoa
Ancestral colonial choanoflagellate
3
LE 33-3a
A jelly
A sponge
0.5 mm
250 µm
A placozoan (LM)
A kinorhynch (LM)
A rotifer (LM)
A marine flatworm
Ectoprocts
Phoronids
4
LE 33-3b
A ribbon worm
A brachiopod
5 mm
An acanthocephalan
A ctenophore, or comb jelly
An octopus
A marine annelid
50 µm
A loriciferan (LM)
A priapulan
5
LE 33-3c
A roundworm
A scorpion (an arachid)
100 µm
100 µm
Tardigrades (colorized SEM)
A cycliophoran (colorized SEM)
An onychophoran
An acorn worm
A sea urchin
A tunicate
6
Sponges

• Characteristics
• Suspension feeders
• Hermaphrodites
• Sessile
• Structure
• Spongocoel
• Osculum
• Choanocytes
• Mesohyl
• Amoebocytes

7
LE 33-4
Food particles in mucus
Flagellum
Choanocyte
Choanocytes
Collar
Osculum
Azure vase sponge (Callyspongia plicifera)
Spongocoel
Phagocytosis of food particles
Amoebocyte
Porocytes
Spicules
Epidermis
Water flow
Amoebocyte
Mesohyl
8
Cnidarians

• Characteristics
• Radial symmetry
• Gastrovascular cavity
• Cnidocytes, cnidae, and nematocysts
• Carnivores
• Body plan
• Polyps
• Medusa

9
LE 33-5
Mouth/anus
Tentacle
Polyp
Medusa
Gastrovascular cavity
Gastrodermis
Mesoglea
Body stalk
Epidermis
Tentacle
Mouth/anus
10
LE 33-6
Prey
Tentacle
Trigger
Discharge of thread
Nematocyst
Coiled thread
Cnidocyte
11
Four classes of Cbidaria

• Hydrozoans
• Both polyp and medusa stages
• Scyphozoans
• Poly stage reduced, free-swimming
• Cubozoans
• Box-shaped medusae, complex eyes
• Anthozoans
• No medusa stage, most sessile

12
Table 33-1
13
LE 33-7
Scyphozoans (jellies)
Cubozoan (sea wasp)
Anthozoan (sea anemone)
Hydrozoans
14
LE 33-83
Reproductive polyp
Feeding polyp
Medusa bud
MEIOSIS
Gonad
Medusa
Sperm
Egg
SEXUAL REPRODUCTION
ASEXUAL REPRODUCTION (BUDDING)
Portion of a colony of polyps
FERTILIZATION
Zygote
Developing polyp
Mature polyp
Planula (larva)
Key
Haploid (n)
1 mm
Diploid (2n)
15
Clade Bilateria (Bilateral symmetry)Phyla

• Platyhelminthes (Flatworms)
• Live in marine, freshwater and damp terrestrial
  habitats
• Acoelomates, triplobastic development
• Flat shape - adaptation
• Rotifera
• Live in marine, freshwater and damp soil
• Alimentary canal replaces gastrovascular cavity
• Pseudocoelomates
• Parthenogenesis

16
Table 33-2
17
LE 33-10
Pharynx
Gastrovascular cavity
Eyespots
Ganglia
Ventral nerve cords
18
LE 33-12
Proglottids with reproductive structures
200 µm
Scolex
Hooks
Sucker
19
LE 33-13
0.1 mm
20
More Phyla of Bilateria

• Lophophorates
• Ectoprocta, Phoronida, and Brachiopoda
• Have lophphore
• U-shaped alimentary canal
• No distinct head
• Nemertea
• Ribbon worms
• Have alimentary canal (unlike flatworms)
• Closed circulatory system (unlike flatworms)

21
LE 33-14
Lophophore
Lophophore
Ectoprocts
Phoronids
Brachiopods
22
Figure 33-15
23
Molluscs

• Snails, slugs, oysters, clams, octopi, squid
• Most marine
• Soft-bodied, hard shell (most)
• Similar body plan
• Muscular foot
• Visceral mass
• Mantle
• Many also have mantle cavity, radula
• Life cycle most have separate sexes, larval
  stage (trochophore)

24
LE 33-16
Visceral mass
Coelom
Heart
Intestine
Nephridium
Gonads
Mantle
Stomach
Radula
Mantle cavity
Shell
Mouth
Radula
Anus
Gill
Mouth
Nerve cords
Foot
Esophagus
25
Figure 33-17
26
LE 33-18
A land snail
A sea slug. Nudibranchs, or sea slugs, lost
their shell during their evolution.
27
LE 33-19
Stomach
Intestine
Mantle cavity
Anus
Mouth
28
Figure 33-20
29
LE 33-21
Coelom
Hinge area
Mantle
Gut
Heart
Adductor muscle
Shell
Anus
Mouth
Excurrent siphon
Palp
Water flow
Foot
Incurrent siphon
Mantle cavity
Gill
30
LE 33-22
Squids are speedy carnivores with beaklike jaws
and well-developed eyes.
Chambered nautiluses are the only living
cephalopods with an external shell.
Octopuses are considered among the most
intelligent invertebrates.
31
Annelids Segmented worms
32
LE 33-23
Cuticle
Coelom
Epidermis
Septum (partition between segments)
Circular muscle
Longitudinal muscle
Metanephridium
Anus
Dorsal vessel
Chaetae
Intestine
Ventral vessel
Nerve cords
Nephrostome
Metanephridium
Clitellum
Esophagus
Crop
Pharynx
Intestine
Giant Australian earthworm
Cerebral ganglia
Gizzard
Mouth
Ventral nerve cords with segmental ganglia
Subpharyngeal ganglion
Circulatory system
33
Nematodes

• Roundworms
• No segmented body, cylindrical bodies
• Pseudocoelomates
• Have a cuticle
• Mostly sexual reproduction
• Examples
• C. elegans
• Trichinella spiralis

34
LE 33-26
25 µm
35
LE 33-27
Encysted juveniles
Muscle tissue
50 µm
36
Arthropods

• General characteristics
• Segmented
• Coelomates
• Exoskeletons
• Open circulatory systems
• Specialized organs for gas exchange

37
Table 33-5
38
LE 33-29
Cephalothorax
Abdomen
Thorax
Head
Antennae (sensory reception)
Swimming appendages (two sets located
under abdomen
Walking legs
Pincer (defense)
Mouthparts (feeding)
39
Figure 33-30
40
LE 33-31
50 µm
Scorpions have pedipalps that are pincers
specialized for defense and the capture of food.
The tip of the tail bears a poisonous stinger.
Dust mites are ubiquitous scavengers in human
dwellings but are harmless except to those people
who are allergic to them (colorized SEM).
Web-building spiders are generally most active
during the daytime.
41
LE 33-32
Stomach
Intestine
Brain
Heart
Digestive gland
Eyes
Ovary
Poison gland
Anus
Book lung
Gonopore (exit for eggs)
Spinnerets
Pedipalp
Chelicera
Sperm receptacle
Silk gland
42
Figure 33-33
43
Figure 33-34
44
LE 33-35
Abdomen
Thorax
Head
Compound eye
Antennae
Dorsal artery
Crop
Cerebral ganglion
Heart
Anus
Vagina
Malpighian tubules
Ovary
Tracheal tubes
Mouthparts
Nerve cords
45
LE 33-36
Larva (caterpillar)
Pupa
Pupa
Emerging adult
Adult
46
LE 33-37aA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Blattodea
4,000
Cockroaches have a dorsoventrally flattened body,
with legs modified for rapid running. Forewings,
when present, are leathery, whereas hind wings
are fanlike. Fewer than 40 cockroach species live
in houses the rest exploit habitats ranging from
tropical forest floors to caves and deserts.
German cockroach
47
LE 33-37bA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Beetles comprise the most species-rich order of
insects. They have two pairs of wings, one of
which is thick and leathery, the other
membranous. They have an armored exoskeleton and
mouthparts adapted for biting and chewing.
Beetles undergo complete metamorphosis.
Coleoptera
350,000
Japanese beetle
48
LE 33-37cA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Earwigs are generally nocturnal scavengers. While
some species are wingless, others have two pairs
of wings, one of which is thick and leathery, the
other membranous. Earwigs have biting mouthparts
and large posterior pincers. They undergo
incomplete metamorphosis.
Dermaptera
1,200
Earwig
49
LE 33-37dA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Dipterans have one pair of wings the second pair
has become modified into balancing organs called
halteres. Their head is large and mobile their
mouthparts are adapted for sucking, piercing, or
lapping. Dipterans undergo complete
metamorphosis. Flies and mosquitoes are among the
best-known dipterans, which live as scavengers,
predetors, and parasites.
Diptera
151,000
Horsefly
50
LE 33-37eA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Hemiptera
Hemipterans are so-called true bugs, including
bed bugs, assassin bugs, and chinch bugs.
(Insects in other orders are sometimes
erroneously called bugs.) Hemipterans have two
pairs of wings, one pair partly leathery, the
other membranous. They have piercing or sucking
mouthparts and undergo incomplete metamorphosis.
85,000
Leaf- footed bug
51
LE 33-37fA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Hymenoptera
Ants, bees, and wasps are generally highly social
insects. They have two pairs of membranous wings,
a mobile head, and chewing or sucking mouthparts.
The females of many species have a posterior
stinging organ. Hymenopterans undergo complete
metamorphosis.
125,000
Cicada-killer wasp
52
LE 33-37gA
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
2,000
Termites are widespread social insects that
produce enormous colonies. It had been estimated
that there are 700 kg of termites for every
person on Earth! Some termites have two pairs of
membranous wings, while others are wingless. They
feed on wood with the aid of microbial symbionts
carried in specialized chambers in their hindgut.
Isoptera
Termite
53
LE 33-37aB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Butterflies and moths are among the best-known
insects. They have two pairs of wings covered
with tiny scales. To feed, they uncoil a long
proboscis. Most feed on nectar, but some species
feed on other substances, including animal blood
or tears.
Lepidoptera
120,000
Swallowtail butterfly
54
LE 33-37bB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Odonata
Dragonflies and damselflies have two pairs of
large, membranous wings. They have an elongated
abdomen, large, compound eyes, and chewing
mouthparts. They undergo incomplete metamorphosis
and are active predators.
5,000
Dragonfly
55
LE 33-37cB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
ORDER
EXAMPLES
Orthoptera
13,000
Grasshoppers, crickets, and their relatives are
mostly herbivorous. They have large hind legs
adapted for jumping, two pairs of wings (one
leathery, one membranous), and biting or chewing
mouthparts. Males commonly make courtship sounds
by rubbing together body parts, such as a ridge
of their hind leg. Orthopterans undergo
incomplete metamorphosis.
Katydid
56
LE 33-37dB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
ORDER
EXAMPLES
Phasmida
2,600
Stick insects and leaf insects are exquisite
mimics of plants. The eggs of some species even
mimic seeds of the plants on which the insects
live. Their body is cylindrical or flattened
dorsoventrally. They lack forewings but have
fanlike hind wings. Their mouthparts are adapted
for biting or chewing.
Stick insect
57
LE 33-37eB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Phthiraptera
2,400
Commonly called sucking lice, these insects spend
their entire life as an ectoparasite feeding on
the hair or feathers of a single host. Their
legs, equipped with clawlike tarsi, are adapted
for clinging to their hosts. They lack wings and
have reduced eyes. Sucking lice undergo
incomplete metamorphosis.
Human body louse
58
LE 33-37fB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
ORDER
EXAMPLES
Siphonaptera
2,400
Fleas are bloodsucking ectoparasites on birds and
mammals. Their body is wingless and laterally
compressed. Their legs are modified for clinging
to their hosts and for long-distance jumping.
They undergo complete metamorphosis.
Flea
59
LE 33-37gB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
EXAMPLES
ORDER
Silverfish are small, wingless insects with a
flattened body and reduced eyes. They live in
leaf litter or under bark. They can also infest
buildings, where they can become pests.
Thysanura
450
Silverfish
60
LE 33-37hB
APPROXIMATE NUMBER OF SPECIES
MAIN CHARACTERISTICS
ORDER
EXAMPLES
Trichoptera
7,100
The larvae of caddisflies live in streams, where
they make houses from sand grains, wood
fragments, or other material held together by
silk, Adults have two pairs of hairy wings and
chewing or lapping mouthparts. They undergo
complete metamorphosis.
Caddisfly
61
Figure 33-38a
62
Figure 33-38b
63
Figure 33-38c
64
Echinoderms

• Deuterostomes (like chordates)
• Slow-moving or sessile
• Endoskeletons
• Water vascular system and tube feet
• Sexual reproduction
• Larvae bilateral, adults radial symmetry

65
Table 33-6
66
LE 33-40
A sea star (class Asteroidea)
A brittle star (class Ophiuroidea)
A sea urchin (class Echinoidea)
A feather star (class Crinoidea)
A sea cucumber (class Holothuroidea)
A sea daisy (class Concentricycloidea)
67
Table 33-7