1. Chapter 33
Invertebrates

2. Fig. 33-1
Figure 33.1 What function do the red whorls of this organism have?

3. Overview: Life Without a Backbone
Invertebrates are animals that lack a backbone
They account for 95% of known animal species

4. Sponges/ “Porifera” Calcarea and Silicea ANCESTRAL PROTIST Cnidaria
Fig. 33-2
Calcarea
and Silicea
Sponges/
“Porifera”
ANCESTRAL
PROTIST
Cnidaria
Common
ancestor of
all animals
Mollusca/
Annelida
Eumetazoa
Nematoda/
Arthropoda
Figure 33.2 Review of animal phylogeny
Bilateria
Chordata/
Echinodermata

5. Phylum Choanocytes Phylum Cnidaria (“Porifera”)
Fig. 33-3a
A jelly
A sponge
Figure 33.3 Invertebrate diversity
Phylum Choanocytes Phylum Cnidaria
(“Porifera”)

6. Phylum Platyhelminthes Phylum Rotifera
Fig. 33-3a
A marine flatworm
A rotifer (LM)
Figure 33.3 Invertebrate diversity
Phylum Platyhelminthes Phylum Rotifera

7. Phylum Mollusca Phylum Annelida
Fig. 33-3m
An octopus
A marine annelid
Figure 33.3 Invertebrate diversity
Phylum Mollusca Phylum Annelida

8. Phylum Nematoda Phylum Arthropoda
Fig. 33-3s
Figure 33.3 Invertebrate diversity
A scorpion
(an arachnid)
A roundworm
Phylum Nematoda Phylum Arthropoda

9. Phylum Echinodermata Phylum Chordata
Fig. 33-3v
A sea urchin
Figure 33.3 Invertebrate diversity
A tunicate
Phylum Echinodermata Phylum Chordata

10. Concept 33.1: Sponges are basal animals that lack true tissues
Sponges are sedentary, filter feeding animals from the phyla Calcarea and Silicea “Porifera”
They live in both fresh and marine waters
Sponges lack true tissues and organs
Possess collar cells to propel water through the body and strain food particles.
Food digested intracellularly by amebocytes
Most asymmetrical
(sponge feeding)

11. Azure vase sponge (Callyspongia plicifera)
Fig. 33-4
Food particles
in mucus
Flagellum
Choanocyte
Choanocyte
Collar
Osculum
Azure vase sponge (Callyspongia
plicifera)
Spongocoel
Phagocytosis of
food particles
Amoebocyte
Pore
Spicules
Figure 33.4 Anatomy of a sponge
Epidermis
Water
flow
Amoebocytes
Mesohyl

12. Concept 33.2: Cnidarians are an ancient phylum of eumetazoans
All animals except sponges and a few other groups are animals with true tissues (Eumetazoa)
Phylum Cnidaria: jellies, corals, sea anemones
Radial symmetrical carnivores
Diplobastic - Two body layers: ectoderm & endoderm
Possess gastrovascular cavity (not a complete tube) and nematocysts
There are two variations on the body plan: the sessile polyp and motile medusa

13. Mouth/anus Tentacle Polyp Medusa Gastrovascular cavity Gastrodermis
Fig. 33-5
Mouth/anus
Tentacle
Polyp
Medusa
Gastrovascular
cavity
Gastrodermis
Mesoglea
Body
stalk
Epidermis
Figure 33.5 Polyp and medusa forms of cnidarians
Tentacle
Mouth/anus

14. Tentacle Cuticle of prey Thread Nematocyst “Trigger” Thread discharges
Fig. 33-6
Tentacle
Cuticle
of prey
Thread
Nematocyst
“Trigger”
Figure 33.6 A cnidocyte of a hydra
Thread
discharges
Thread
(coiled)
Cnidocyte

15. (a) Colonial polyps (class Hydrozoa)
Fig. 33-7
(b) Jellies (class
Scyphozoa)
(c)
Sea wasp (class
Cubozoa)
(d) Sea anemone (class
Anthozoa)
Figure 33.7 Cnidarians
(a) Colonial polyps (class
Hydrozoa)

16. Conceptual Summary
Sponges and cnidarians are almost entirely marine and are considered primitive because they do not possess three body layers nor true organs
(hydra eating)
(budding in hydra)

17. Reproductive polyp Feeding polyp Medusa bud Medusa ASEXUAL
Fig
Reproductive
polyp
Feeding
polyp
Medusa
bud
Medusa
ASEXUAL
REPRODUCTION
(BUDDING)
Portion of
a colony
of polyps
Figure 33.8 The life cycle of the hydrozoan Obelia
1 mm
Key
Haploid (n)
Diploid (2n)

18. Reproductive polyp Feeding polyp Medusa bud Gonad Medusa Egg Sperm
Fig
Reproductive
polyp
Feeding
polyp
Medusa
bud
MEIOSIS
Gonad
Medusa
Egg
Sperm
SEXUAL
REPRODUCTION
ASEXUAL
REPRODUCTION
(BUDDING)
Portion of
a colony
of polyps
FERTILIZATION
Figure 33.8 The life cycle of the hydrozoan Obelia
Zygote
1 mm
Key
Haploid (n)
Diploid (2n)

19. Medusa produced by asexual budding Reproductive polyp Feeding polyp
Fig
Medusa produced
by asexual budding
Reproductive
polyp
Feeding
polyp
Medusa
bud
MEIOSIS
Gonad
Medusa
Egg
Sperm
SEXUAL
REPRODUCTION
ASEXUAL
REPRODUCTION
(BUDDING)
Portion of
a colony
of polyps
FERTILIZATION
Figure 33.8 The life cycle of the hydrozoan Obelia
Zygote
1 mm
Developing
polyp
Planula
(larva)
Key
Mature
polyp
Haploid (n)
Diploid (2n)

20. Platyhelminthes: Flatworms
Acoelomates – solid body, without a body cavity
Bilateral symmetry and beginnings of cephalization
Development of true organs, tripbloblastic (three body layers); ectoderm, endoderm, mesoderm
No coelom (body cavity)
Digestibe tract incomplete – only one opening that braches throughout the body to distribute food
(flatworm mating behavior – Rated R)

21. Fig. 33-9
Figure 33.9 A marine flatworm (class Turbellaria)

22. Pharynx Gastrovascular cavity Mouth Eyespots Ganglia
Fig
Pharynx
Gastrovascular
cavity
Mouth
Figure Anatomy of a planarian, a turbellarian
Eyespots
Ganglia
Ventral nerve cords

23. Tapeworms are parasites of vertebrates and lack a digestive system
Fig
Tapeworms are parasites of vertebrates and lack a digestive system
Tapeworms absorb nutrients from the host’s intestine
Fertilized eggs, produced by sexual reproduction, leave the host’s body in feces
200 µm
Proglottids with
reproductive structures
Hooks
Sucker
Figure Anatomy of a tapeworm
Scolex

24. Rotifera
Pseudocoelomates – body cavity between digestibe tract and body wall is not completely lined by mesoderm
Rotifers have an alimentary canal, a digestive tube with a separate mouth and anus (complete digestive tract) that lies within a fluid-filled pseudocoelom
(rotifer feeding)

25. Jaws Crown of cilia Anus Stomach 0.1 mm Fig. 33-13
Figure A rotifer
Anus
Stomach
0.1 mm

26. Nematoda: Roundworms
Nematodes, or roundworms, are found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals
Pseudocoelomates
They have an alimentary canal, but lack a circulatory system
Reproduction in nematodes is usually sexual, by internal fertilization
(C. elegans crawling)

27. Fig
Figure A free-living nematode (colorized SEM)
25 µm

28. Conceptual Summary
Flatworms and roundworms have bilateral symmetry, the beginnings of cephalization, and three body layers with well developed tissues and organs. Phyla include many important parasites of humans.

29. All of the animals that we cover from this point on are coelomates – body cavity (coelom) is completely lined by mesoderm. Groups are divided as protostomes or deuterostomes

30. Mollusca
Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids
Basic body plan of muscular head-food, with body on top a loosely covered mantle which may secrete a shell
Gastropods have a well defined head, tentacles and elongated flattened foot
Marine and freshwater filter feeders have a body flattened between two valves of a hinged she. Bivalvia
Cephalopods are on the the most advanced invertebrate groups (octopus, squid, nautilus)
Protostomes

31. Nephridium Visceral mass Heart Coelom Intestine Gonads Mantle Stomach
Fig
Nephridium
Visceral mass
Heart
Coelom
Intestine
Gonads
Mantle
Stomach
Mantle
cavity
Shell
Mouth
Radula
Anus
Gill
Figure The basic body plan of a mollusc
Radula
Mouth
Nerve
cords
Foot
Esophagus

32. Fig
Figure A chiton

33. Fig
(a) A land snail
Figure Gastropods
(b) A sea slug

34. Fig
Figure A bivalve

35. Coelom Hinge area Mantle Gut Heart Adductor muscle Digestive gland
Fig
Coelom
Hinge area
Mantle
Gut
Heart
Adductor
muscle
Digestive
gland
Anus
Mouth
Excurrent
siphon
Figure Anatomy of a clam
Shell
Water
flow
Palp
Foot
Incurrent
siphon
Mantle
cavity
Gonad
Gill

36. Fig
Octopus
Squid
Figure Cephalopods
Chambered
nautilus

37. http://www. youtube. com/watch
(squid inking) (nautilus)

38. Annelida: Segmented Worms
Possess a coelom and closed circulatory system
Body segmented - septa
Protostomes

39. Giant Australian earthworm Pharynx Intestine
Fig
Cuticle
Septum
(partition
between
segments)
Epidermis
Coelom
Circular
muscle
Metanephridium
Longitudinal
muscle
Anus
Dorsal vessel
Chaetae
Intestine
Fused
nerve
cords
Ventral
vessel
Nephrostome
Metanephridium
Clitellum
Figure Anatomy of an earthworm, an oligochaete
Esophagus
Crop
Giant Australian earthworm
Pharynx
Intestine
Cerebral ganglia
Gizzard
Mouth
Ventral nerve cord with
segmental ganglia
Subpharyngeal
ganglion
Blood
vessels

40. Fig
Figure A polychaete
Parapodia

41. Fig
Figure A leech

42. Arthropoda: (jointed foot)
Major evolutionary advances over other invertebrate groups include exoskeleton (chitin) and jointed appendages
Open circulatory system in which fluid called hemolymph is circulated into the spaces surrounding the tissues and organs (fig pg. 900)
Main groups are arachnids (spiders, ticks), crustaceans (lobsters, crabs, shrimp, krill), and insects
Rotostomes

43. Cephalothorax Abdomen Antennae (sensory reception) Thorax Head
Fig
Cephalothorax
Abdomen
Antennae
(sensory
reception)
Thorax
Head
Swimming appendages
(one pair located
under each
abdominal segment)
Figure External anatomy of an arthropod
Walking legs
Pincer (defense)
Mouthparts (feeding)

44. Fig
Figure Horseshoe crabs (Limulus polyphemus)

45. Scorpion Dust mite Web-building spider 50 µm Fig. 33-31
Figure Arachnids
Web-building spider

46. Arachnids have an abdomen and a cephalothorax, which has six pairs of appendages, the most anterior of which are the chelicerae
Gas exchange in spiders occurs in respiratory organs called book lungs
Many spiders produce silk, a liquid protein, from specialized abdominal glands

47. Stomach Intestine Heart Brain Digestive gland Eyes Ovary Poison gland
Fig
Stomach
Intestine
Heart
Brain
Digestive
gland
Eyes
Ovary
Poison
gland
Figure Anatomy of a spider
Book lung
Anus
Gonopore
(exit for eggs)
Chelicera
Pedipalp
Spinnerets
Sperm
receptacle
Silk gland

48. Fig
Figure A millipede

49. Fig
Figure A centipede

50. Abdomen Thorax Head Compound eye Antennae Heart Cerebral ganglion
Fig
Abdomen
Thorax
Head
Compound eye
Antennae
Heart
Cerebral ganglion
Dorsal
artery
Crop
Anus
Vagina
Figure Anatomy of a grasshopper, an insect
Malpighian
tubules
Ovary
Tracheal tubes
Mouthparts
Nerve cords

51. Flight is one key to the great success of insects
An animal that can fly can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl
Many insects undergo metamorphosis during their development
In incomplete metamorphosis, the young, called nymphs, resemble adults but are smaller and go through a series of molts until they reach full size
Insects with complete metamorphosis have larval stages known by such names as maggot, grub, or caterpillar
The larval stage looks entirely different from the adult stage
(butterfly metamorphosis)

52. (a) Larva (caterpillar) (b) Pupa (c) Later-stage pupa (d) Emerging
Fig
(a) Larva (caterpillar)
(b) Pupa
(c) Later-stage
pupa
Figure Metamorphosis of a butterfly
(d) Emerging
adult
(e) Adult

53. Most insects have separate males and females and reproduce sexually
Individuals find and recognize members of their own species by bright colors, sound, or odors
Some insects are beneficial as pollinators, while others are harmful as carriers of diseases, or pests of crops

54. Crustaceans
While arachnids and insects thrive on land, crustaceans, for the most part, have remained in marine and freshwater environments
Crustaceans, subphylum Crustacea, typically have branched appendages that are extensively specialized for feeding and locomotion
Most crustaceans have separate males and females

55. (a) Ghost crab (b) Krill (c) Barnacles Fig. 33-38
Figure Crustaceans
(b) Krill
(c) Barnacles

56. Conceptual Summary
The chitinous exoskeleton of arthropods, with its many jointed appendages modified for a variety of jobs, proved so versatile that the arthropods have undergone impressive adaptive radiation with more species and individuals than any other phylum

57. Concept 33.5: Echinoderms and chordates are deuterostomes
Sea stars and other echinoderms, phylum Echinodermata, may seem to have little in common with phylum Chordata, which includes the vertebrates
Shared characteristics define deuterostomes (Chordates and Echinoderms)
Radial cleavage
Formation of the mouth at the end of the embryo opposite the blastopore

58. Echinodermata: Sea urchins, sea stars and sea cucumbers
Sea stars and most other echinoderms are slow-moving or sessile marine animals
Deuterostomes
Vertebrates are more closely related to echinoderms than to annelids, mollusks or arthropods based on studies of embryonic development
Echinoderms have a unique water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange
Possess a skeleton of calcium carbonate just under the skin
Immature have bilateral symmetry, however, most adults have pentaradial symmetry
(sea star feeding)

59. Stomach Anus Spine Gills Central disk Digestive glands Madreporite
Fig
Stomach
Anus
Spine
Gills
Central disk
Digestive glands
Madreporite
Radial
nerve
Figure Anatomy of a sea star, an echinoderm
Gonads
Ring
canal
Ampulla
Podium
Radial canal
Tube
feet

60. (a) A sea star (class Asteroidea)
Fig a
Figure Echinoderms
(a) A sea star (class Asteroidea)

61. (b) A brittle star (class Ophiuroidea)
Fig b
Figure Echinoderms
(b) A brittle star (class Ophiuroidea)

62. (c) A sea urchin (class Echinoidea)
Fig c
Figure Echinoderms
(c) A sea urchin (class Echinoidea)

63. (d) A feather star (class Crinoidea)
Fig d
Figure Echinoderms
(d) A feather star (class Crinoidea)

64. (e) A sea cucumber (class Holothuroidea)
Fig e
Figure Echinoderms
(e) A sea cucumber (class Holothuroidea)

65. (f) A sea daisy (class Concentricycloidea)
Fig f
Figure Echinoderms
(f) A sea daisy (class Concentricycloidea)

66. Chordates
Phylum Chordata consists of two subphyla of invertebrates as well as hagfishes and vertebrates
Chordates share many features of embryonic development with echinoderms, but have evolved separately for at least 500 million years

67. You should now be able to:
List the characteristics of the phylum “Porifera”
List the characteristics of the phylum Cnidaria that distinguish it from other animal phyla
List the characteristics of Platyhelminthes
List the characteristics of Mollusca
List the characteristics of Annelida
List the characteristics of Nematoda
List three features that account for the success of Arthropods
Describe the developmental similarities between echinoderms and chordates