1. PHYLUM MOLLUSCA not drab and mundane as found on the N.A. continent
of the eight classes, only 3 are common
“MALACOLOGY”
The study of molluscs

2. 50, ,000 living species
35,000 extinct species
Largest = 1000 lbs.
80% less than 5 cm

3. Classes of Mollusca Class Bivalvia (Clams, oysters)
Class Gastropoda (snails, slugs)
Class Cephalopoda (Squid, octopus)
Class Polyplacophora (Chitons)
Additional classes not covered
Class Scaphopoda
Class Caudofoveata
Class Solengastres
Class Monoplacophora

4. Unifying characteristics “INDICATORS OF COMMON ANCESTRY”
1. Visceral mass (internal organs) heart, digestion excretion, reproduction
2. Mantle- tissue surrounding the visceral cavity, secretes shell (which may be present or absent)
3. Muscular foot - organ for propulsion
4. Head- mouth, sense organs, cerebral ganglia
5. Trochophore- juvenile larvae form

5. 6. Radula
Ribbon of small teeth that are used to feed
Made of chitin
7. Siphon
8. Gas exchange through gills
Habitat
Fresh and salt water and a few terrestrial

6. Trochophore Larva
All the members of this phylum start their life as a free living “trochophore”

7. Generalized Mollusk Anatomy
Fig. 16.2

8. Body Plan Pericardial cavity Metanephridium Mantle cavity Gonad
Ctenidium
Radula
Foot
Stomach and digestive gland

9. Dorsal mantle covers the visceral mass.

10. Secretes the shell

11. Ctenidium (Respiration)

12. Complete digestive system

13. Paired ventral nerve cords

14. Radula

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Radular Structure
Source: From A Life of Invertebrates, Copyright © 1979 W. D. Russell-Hunter.

16. Radula

18. Coelom - metanephridia
Skip this diagram

19. CLASSES

20. Class Polyplacophora Chitons
Fig. 16.1a

21. Class Polyplacophora Eight dorsal plates Reduced head
Radula reinforced with iron
Scrape algae from rocks
Multiple gills, along sides of body between foot and mantle edge

22. Class Polyplacophora
Mouth
Mantle cavity
Ctenidium
Foot
Anus

23. Class Polyplacophora Stomach Gonad Digestive gland Pericardial cavity
Mouth
Nephridium
Anus

24. Chitons

26. Class Gastropoda Snails, Slugs, Conchs, Limpets

27. Class Gastropoda
“STOMACH FOOT”
One shell (if present)
single muscular foot
- operculum- trap door to close for protection
- radula- scraping tongue
- can be parasites
-some can have symbiotic relationship with algae "zooxanthellae”

28. Torsion of body
Fig

29. Batton the Hatches! Snails have a trap door called the operculum
They can close it to prevent water loss or to avoid being eaten!

30. Snail
Terrestrail
Mantle cavity functions as lung

31. Snail Pneumostome Tentacle (Eye stalks) Shell Anus Tentacle Foot Mouth
Genital pore

32. Internal Structure of a Generalized Gastropod
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Internal Structure of a Generalized Gastropod

33. Helix – garden snail
I’ll get there by midnight, I think…

34. Nudibranch
No shell
Dorsal projections
Gills
Nematocyst discharge

35. Abalone
Several holes in top of shell
Excrete waste
Food for man

36. Interesting but don’t write this?
Nudibranchs
Gastropods that have lost their shell
Breathe through their cerata (colorful branches on their dorsal side)
Often produce toxic chemicals for protection
Or steal undischarged nematocysts taken from their prey.

37. Slug
No shell
Garden pests

38. Limpet
Herbivores
Cling to rocks or other surfaces

39. Conch
Large shell
Marine
Many are predators

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44. Class Bivalvia Clams, Oysters, Shipworms

45. Class Bivalvia Two shells
shell has two lateral valves with dorsal hinge
Most are filter feeders
No head or radula
Body enclosed in mantle
Head greatly reduced
No radula
No eyes, a few species with eyes on mantle margin
foot usually wedge-shaped
Burrow
Sand, wood, rocks

46. Fig b

47. Fig

48. Giant Clam & Burrowing Clam
Siphon

49. It’s Like a Straw Siphon – tube that sticks out of shell
Incurrent siphon takes in water carrying food and oxygen
Excurrent siphon carries water containing wastes and CO2 out
Gooey duct

50. Bivalves Body is laterally compressed Two shells, hinged together
No head, no radula
Gills used to obtain oxygen and to filter out small food particles from the water
Adductor muscles keep shells closed
As bivalve grows, it adds a layer to its shell
Bivalves

51. Figure 16.31a

52. Clam Dissection

53. The Blue Mussel Uses byssal threads to attach to the substrate
Threads are secreted by the mussel’s foot
Anchors mussel in place on rocks to make filter feeding easier
Experimented with as a dental adhesive

54. Scallops

55. Shipworms

56. Class Cephalopoda Squids, Octopuses, Nautiluses

57. Giant Squid
“A live giant squid (Architeuthis) measuring roughly 25 feet long attacks a baited fishing line off the Ogasawara Islands. Japanese scientists recently released the first-ever images of a live giant squid in the wild. Many giant squid have washed up on beaches or have been found dead or dying in fishing nets. This specimen was found in New Zealand in 1996.”

58. http://news. nationalgeographic. com/news/2006/12/061222-giant-squid

59. - Intelligent and have a complex eye (as in humans) can form images by moving the lens in and out (How do we focus?)
- chromatophore- pigment sacks with the 3 primary colors. Nerves cause them to expand and contract. (spots to dots)
- octopus crawls and squids swim in schools (jet propulsion)
Marine

60. Copyright © The McGraw-Hill Companies, Inc
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cephalopod Eye

61. Class Cephalopoda Shell in squid and octopus absent or vestigial
Ink sac
Foot modified into arms and tentacles
All predators
high extinction 10,000 fossils down to 400 species today

62. Ammonoids Extinct Devonian to Cretaceous Died out with dinosaurs
400 to 65 MYA
Died out with dinosaurs

63. Squid “you will learn this when we do the dissection”
Posterior surface
Right
Ventral
Dorsal
Left

64. Squid
Tentacle
Arm
Funnel (siphon)
Fin
Collar
Eye

65. Squid
Shell (Pen)
Systemic
heart
Branchial heart
Ctenidium
Funnel 4

66. Squid Male
Testis
Penis
Hectocotylous arm

67. Squid Female Ovary with eggs Oviducal gland Nidamental glands
Oviducal opening

68. Octopus
Eight arms with suckers
Most intelligent invertebrate

69. Cuttlefish

70. Who Wants a Snack? Catches prey with tentacles
Suction disks on tentacles used to grasp and hold prey
Bite from beak kills prey
Poisonous venom in some cases

71. Squid

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74. Nautilus Up to 94 tentacles Shell with many chambers No suckers
Lives in outermost chamber

75. Chambered Nautilus

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77. But They Don’t Have Shells! How do they protect themselves?
Fast swimmers (jet propulsion)
Force water out the mantle cavity through the siphon. The siphon can move and point the animal in any direction
Camouflage: Chromatophores
Ink Cloud
Intelligence
Vision

78. Economics Pearls Burrowing shipworms Snails & slugs Garden pests Food
Intermediate hosts for parasites

79. Oysters

80. Pearl formation Shell Developing pearl Epithelium
Irritant lodged between shell and mantle
Layers of nacre secreted around foreign material

81. Zebra Mussel Environmental Pest
Ballast water of ships from Europe in 1986
Attack be secreting adhesive byssal threads
Each other
Other mussels
Man made objects
Pipes, plumbing

82. Zebra Mussel Live in high densities Feed on phytoplankton
Reproduce rapidly

83. Zebra Mussel Attach to native mussels
Killed all native mussels in Lake Erie

84. Distribution of Zebra Mussel