1. Mollusca & Annelida

2. invertebrates protostomes Mollusca Annelida Porifera Metazoa
ANCESTRAL
PROTIST
Ctenophora
Metazoa
Cnidaria
Eumetazoa
Acoela
Single common animal ancestor
Hemichordata
Echinodermata
True Tissues
Deuterostomia
Bilateria
Chordata
Bilateral &
3 germ layers
Platyhelminthes
invertebrates
Rotifera
Ectoprocta
Figure A phylogeny of living animals
Lophotrochozoa
Brachiopoda
protostomes
Mollusca
Annelida
Nematoda
Ecdysozoa
Arthropoda

3. Mollusca Body Plan Ceolomates (true coelum) 3 main body parts
Often very reduced/small
3 main body parts
Muscular foot (for movement)
Visceral mass (w/ most internal organs)
Mantle
Creates calcium based shell
mantle cavity in some (containing gills, anus, and pores)
Shell in most
Protection against predation & dessication

4. Mollusk organ systems Feeding & Digestive:
Many feed with a rasp-like strap called the radula
Herbivores or predators
Filter feeders (using gills or “tentacles”)
Beak (cephalopods)
Complete digestive system w/ specialized organs
Digestive gland (a.k.a. hepatopancrease)
Cardiovascular:
Open (except in cephalopods)
Hemocyanin
Excretory and osmoregulation
Metanephridia

5. Mollusk organ systems Nervous: “brain” encircling pharynx
Two ventral nerve cords (in most)
Respiratory:
Gills
mantle
Reproductive
Most are dioecious w/ gonads in visceral mass
Many gastropods are hermaphrodites
Typically a ciliated larvae known as the trochophore

6. Generic Mollusc Body Plan
Visceral
mass
Metanephridium
Heart
Coelom
Intestine
Digestive tract
Gonads
Mantle
Mantle
cavity
Stomach
Shell
Mouth
Radula
Anus
Gill
Figure The basic body plan of a mollusc
Mouth
Nerve
cords
Foot
Esophagus
Radula

7. radula

8. Four of the major classes of molluscs are
Polyplacophora (chitons)
Gastropoda (snails and slugs)
Bivalvia (clams, oysters, and other bivalves)
Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)

9. Polyplacaphora (Chitons)
Figure A chiton

10. Chitons Oval shaped body 8 dorsal plates
Unsegmented body
Foot acts as suction cup to hold in place (to prevent dislodgement and drying)
Herbivores
use radula to scrap algae off rocks
Adaptation to intertidal zone

12. Gastropods (snails & slugs)
A land snail
Figure Gastropods
(b)
A sea slug (nudibranch)

13. Gastropods ¾ of all mollusc species Move by rippling foot or cilia
Shell, reduced, abscent
Torsion
Most are herbivores using radula to eat
Some predator (radula bores holes or shreds prey)
Many w/ eyes at tip of tentacles
Aquatic  gills for gas exchange
Terrestrial  lining of mantle in mantle cavity for gas exchange

15. Bivalvia (bivalves/ “shellfish”)

16. Bivalves All aquatic Dorsally hinged 2-part shell No distinct head
Adductor muscle holds shell closed
No distinct head
Radula has been lost
Some have eyes and sensory tentacles along the out edge of mantle
Gill in mantel cavity
Gill for filter feeding and gas exchange
Most are suspension feeders
Cilia move food in gills to mouth
Incurrent siphon in, excurrent siphon out
Many are sedentary
Some fix themselves substrates, some move w/ feet

17. Figure 33.19 Coelom Hinge area Mantle Gut Heart Adductor muscle
(one of two)
Digestive
gland
Anus
Mouth
Excurrent
siphon
Figure Anatomy of a clam
Shell
Palp
Water
flow
Foot
Mantle
cavity
Incurrent
siphon
Gonad
Gill

18. Figure 33.20 Cephalopods Squid Octopus Chambered nautilus

19. Cephalopods: Octupus, squid, nautilus, cuttlefish
marine predators
Modified foot
Tentacles (for prey capture)
Excurrent siphon
Beak (some with teeth)
Radula reduced or vestigal
Some poisonous
Move with jet of water out excurrent siphon
Shell is reduces and often internal (except nautilus)
closed circulatory system
Complex brain, eyes, and other sensory organs
Well developed nervous system and senses (e.g., eyes & big brain)

21. Annelida: segmented worms
Divided by septa internally
Marine, freshwater, and damp soil (terrestrial)
BODY PLAN
Long, thin  worm
Coelomates

23. Systems Closed cardiovascular system
Complete digestive system w/ specialization
Metanephridia
Gills, parapodia, or surface gas exchange
“brain” near pharynx
Ventral nerve cord

24. polycheates > oligochaetes > hirudinae
Historical Classes
Polychaetes
Oligochaeates
Hirudinae
Modern relationship:
polycheates > oligochaetes > hirudinae

25. Polycheata: polycheates and tube worms
Parapodia
Figure An errantian, the predator Nereimyra punctata

26. Polycheates Marine Mobile forms are: Parapodia w/ chaetae (“bristles”)
Predators
Herbivores (of large algae)
Scavengers
Parapodia w/ chaetae (“bristles”)
Movement
Can be vascular and used for gas exchange
Well developed jaws and sensory organs

27. Polycheates: tube worms
Filter feeders
Gills or “tentacles”

28. Oligocheates Aquatic and terrestrial Setae
Circular and longitudinal muscles
Hydrostatic skeleton
Peristalsis
Gas exchange over surface
Cross fertilizing hermaphrodites

29. Figure 33.25 Coelom Cuticle Epidermis Septum (partition
between segments)
Circular muscle
Metanephridium
Longitudinal muscle
Dorsal
vessel
Anus
Chaetae
Intestine
Skin
Ventral vessel
Fused
nerve cords
Nephrostome
Clitellum
Esophagus
Figure Anatomy of an earthworm, a sedentarian
Metanephridium
Pharynx
Crop
Intestine
Giant Australian earthworm
Cerebral ganglia
Gizzard
Mouth
Subpharyngeal
ganglion
Ventral nerve cords
Circulatory system vessels

30. Figure 33.25a Anus Skin Metanephridium Clitellum Esophagus Pharynx
Crop
Intestine
Figure 33.25a Anatomy of an earthworm, a sedentarian (part 1: cutaway)
Cerebral
ganglia
Gizzard
Mouth
Subpharyngeal
ganglion
Ventral nerve cords
Circulatory system vessels

31. Figure 33.25b Cuticle Coelom Epidermis Circular muscle
Septum (partition
between segments)
Longitudinal muscle
Metanephridium
Dorsal
vessel
Chaetae
Intestine
Figure 33.25b Anatomy of an earthworm, a sedentarian (part 2: cross section)
Ventral vessel
Nephrostome
Fused
nerve cords

32. Hirudinae
Figure A leech

33. Hirudinae (leeches) predators, scavengers, blood-sucking parasites
Mostly freshwater
Lack setae
Dorso-ventrally flattened
Suckers to hold prey
Subtle segmentation
Blood sucking type
bladelike jaws
aneasthetic saliva
anticoagulant, hirudin
Blood letting v. modern use

34. Circulatory Systems: open v. closed

35. Respiratory Structures

36. nephridiostome
nephridiophore