1. Phylum Molluscs

2. General Name means soft, or soft body
this is one of the largest animal phyla, besides Arthropoda
There are nearly 75,000 species and some 35,000 fossil species
Very diverse group (chitons, snails, clams, octopuses)
Range from simple organisms to some of the most complex invertebrates
Size from microscopic to huge (18 m giant squid)
80% of molluscs are less than 5 cm

3. Molluscs Classes Class Polyplacophora: Chitons Class Gastropoda
Class Bivalvia (Pelecypoda)
Class Cephalopoda

4. Hawaiian Bobtail Squid

5. Blue Ringed Octopus

6. Giant Squid

8. Ecological Relationship
great range of habitats – from tropics to polar, altitudes exceeding 7000 m, ponds, lakes, streams, surf, ocean depths, etc
Most live in the sea
Include herbivores, carnivores, and ciliary filter feeders
Originated in the sea

9. Economic Importance many are food for humans
produce pearls (most from Eastern Asia)
Some molluscs are destructive (Great Lakes, Snails and Slugs in gardens)

14. Form and Function Body Plan –
consist of head-foot portion and a visceral mass
head-foot portion – contains feeding, cephalic sensory, and locomotor organs
visceral mass – contains digestive, circulatory, respiratory, and reproductive organs

16. Form and Function Body Plan –
two folds of skin make up a protective “mantle”
they enclose a space between the mantle and body wall called the “mantle cavity”
it houses gills or lungs
mantle also secretes a shell in many species

18. Form and Function Head-foot –
many have well developed head containing sensory organs
range from simple to complex eyes
posterior of mouth is usually the foot (chief locomotor organ)

19. Form and Function Head-foot –
Unique structure inside mouth called “radula”
It is a rasping, protrusible, tonguelike organ found in all molluscs except bivalves
It is a ribbon-like membrane on which are mounted rows of tiny teeth that point backward
Complex muscles move the radula and its supporting cartilage (odontophore) in and out while the membrane is rotated
It has about 250,000 teeth
When protruded, it can scrape, pierce, tear, or cut food material

23. Radula (Slug Eating)

24. Form and Function Head-foot –
Foot can be adapted for locomotion, attachment, or a combination of functions
Usually a ventral, solelike structure in which muscular contractions create a creeping movement
Some modifications include – “hatchet foot” of bivalves, funnel for jet propulsion in squids and octopuses

25. Form and Function Visceral Mass – (mantle and mantle cavity)
mantle – a sheath of skin extending from the visceral hump that hands down each side of the body, protecting soft parts and creating a space

26. Form and Function Visceral Mass – (mantle and mantle cavity)
mantle cavity – houses respiratory organs
products from digestive, excretory, and reproduction systems empty into the mantle cavity
in aquatic species, surface cilia create water currents that continually flush out waste

28. Form and Function Visceral Mass –
Shell (when present) typically has three layers
Periostracum – outer organic layer
Composed of a protein called “conchiolin”
Growth only occurs at the margin of the shell
Prismatic layer – middle layer
Composed of densely packed prisms of calcium carbonate in a protein matrix
Nacreous layer –
Composed of calcium carbonate sheets laid down over a thin protein matrix
This layer is continuously secreted by mantle surface, so it becomes thicker during the animals life
Calcium for the shell comes from environmental water, soil, or food

29. a. Periostracum, b1. Prismatic layer, b2. Nacreous layer

30. Form and Function Internal Structure and Function –
there is an open circulatory system
pumping heart
blood vessels
blood sinuses
most cephalopods have closed circulatory system

32. Form and Function Internal Structure and Function –
Digestive tract is complex and highly specialized according to feeding habits
Most have a pair of kidneys (metanephridia)
Ducts of kidneys in many forms serve to discharge eggs and sperm

33. Form and Function Internal Structure and Function –
Nervous System consists of several pairs of ganglia with connected nerve cords
Most molluscs are dioecious
Some gastropods are hermaphroditic
Many aquatic species pass through free-swimming “trochophore” and “veliger” larval stages

34. Trochophore

35. Veliger

36. Mating Leopard Slugs

37. Class Polyplacophora: Chitons
are somewhat flattened and have a convex dorsal surface that bears eight plates, or valves
name means “bearing many plates”
most are between 2 and 5 cm
commonly occur on rocky surfaces in intertidal regions
if detached, they can roll up like an Armadillo for protection
Sexes are separate
Eggs are released singly or in strings or masses of jelly

44. Class Gastropoda (gastro – stomach, podos – foot)
By far the largest and most diverse class
Contains about 40,000 living species
Includes snails, limpets, slugs, whelks, conchs, periwinkles, sea slugs, sea hares, sea butterflies, etc.
Often sluggish, sedentary animals
Because of heavy shells and slow locomotor organs

45. Snails

46. Snails

47. Limpets (Owl Limpet)

48. Limpets

49. Slugs

50. Whelks

51. Whelks (Lightening)

52. Conchs

53. Conchs

54. Conchs

55. Periwinkles

56. Periwinkles

57. Sea slugs

58. Sea slugs

59. Sea slugs

60. Frosted Sea Slug

61. Sea hares

62. Sea hare

63. Sea hare

64. Sea butterflies

65. Class Gastropoda
Basically bilaterally symmetrical, but because of “torsion,” the visceral mass is asymmetrical
Torsion – a twisting process that occurs during development

67. Class Gastropoda Three subclasses – Prosobranchia (largest)
Almost all marine
Periwinkles, limpets, whelks, conchs, abalones, slipper shells, oyster borers, rock shells, cowries
Opisthobranchia
Sea slugs, sea hares, nudibranchs, canoe shells
Pulmonata
Mostly land and freshwater snails and slugs
Usually lack gills
Mantle cavity becomes a lung
Usually have two pairs of tentacles, with the posterior pair bearing eyes

68. Nudibranchs

69. Nudibranchs

70. Class Bivalvia (Pelecypoda)
(two-shelled)
Includes mussels, clams, scallops, oysters, shipworms
Most are sedentary “suspension feeders”
Unlike gastropods they have no head, radula, and little cephalization

71. Class Bivalvia (Pelecypoda)
Most are marine, but many live in brackish water and in stream, ponds, and lakes
Their two shells (valves) are held together dorsally by a “hinge ligament”
“Adductor muscles” work in opposition to the hinge ligament and draw the valves together
Zebra mussels (pg 194)

73. Zebra mussels (Lake Mead)

74. Preventing Mussels in IdahoMk

75. Class Cephalopoda most complex species
include squids, octopuses, nautiluses, cuttlefishes
All are marine
All are active predators
Have an odd body plan
Develops as the embryonic head and foot become indistinguishable
The ring around the mouth bears arms and tentacles

76. Class Cephalopoda
Range from 2 to 3 cm to largest of all invertebrates (giant squid)
Giant squid (pg 194)

77. Giant Squid

78. Slash marks from Giant Squid

79. The Search for the Giant Squid

80. Class Cephalopoda
Most have special pigment cells called “chromatophores” in their skin
By expanding and contracting, they produce color change
Some color change are for protection to match the background
Most change is behavioral, associated with alarm or courtship
Many deep-sea squid are bioluminescent
When the animal is alarmed, it releases a cloud of ink through the anus to form a “smokescreen” to confuse an enemy

81. Squid

82. Mimic Octopus and others
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83. Octopuses

84. Octopuses

85. Octopuses

86. Blue Ringed Octopus The most venous octopus.
This small mollusc lives in warm, shallow reefs off the coast of Australia, new Guinea, Indonesia and the Philippines. 
It has a life span of about one and a half years.

87. Blue Ringed Octopus
It is said that the venom of this octopus could kill 26 adults in just a few minutes.
There is no antivenin for treatment.
Fortunately, these octopuses do not attack humans.
Injury typically occurs when a blue-ringed octopus is stepped on or picked up.

88. Smart Veined Octopus using Tools

89. Giant Pacific Octopus vs. Spiny Dogfish Shark

90. Nautiluses

91. Nautiluses

92. Nautiluses

93. Chambered Nautilus

94. Diving for Nautilus

95. Cuttlefishes

96. Cuttlefishes

97. Cuttlefishes

98. Cuttlefish Attacks