Phylum Mollusca

1
Phylum Molluscasoft-bodied
2

• 4 Primary Classes
• Class Gastropoda Snails, conchs, slugs, sea
  slugs, sea hares, limpets, etc. (very diverse)

3
Gastropoda stomach-footedSnails and slugs
4
Class Bivalvia Clams, oysters and scallops
5
Bivalvia two halvesClams, oysters, scallops,
mussels
6
Class Cephalopoda Octopi, squid, nautilis,
cuttlefish
7
Cephalopoda head-footedOctopi, cuttlefish,
squid, nautali
http//www.youtube.com/watch?featureplayer_detail
pagevYVvn8dpSAt0
8
Blue-Ring Octopus
9
(No Transcript)
10
(No Transcript)
11
Cuttlefish
12
(No Transcript)
13
Squid
14
Giant SquidAvg. length35 feet Max.
Length80 feet
15
Colossal SquidMaximum length43 feet
16
http//www.ted.com/talks/david_gallo_ shows_underw
ater_astonishments.html
17
Class Polyplacophora Chitons
18
Body plan

• Bilateral Symmetry
• Muscular foot used for locomotion, burrowing and
  capturing prey
• Mantle, an outgrowth of tissue that covers
• most of its body. This secretes the shell.
• Coelom -Body cavity primarily around heart
• Shell - Made of calcium carbonate, internal or
  external
• Viceral mass the internal organs

19
Feeding

• Complete digestive system
• Herbivores use a radula to scrape algae
• from rocks
• Carnivores use jaws to eat prey
• like the octopus
• Filter feeders use a siphon to catch plankton

20
Respiration

• Gas exchange via gills, lungs
• Land snails respire through a mantle or its body
  surface

21
Circulation

• Open circulatory system- except cephalopods,
  where the blood is transported through the body
  via a cavity called the hemocoel
• Leaving the vessels, blood travels through
  sinuses or large sack-like spaces
• Possess blood vessels by a heart
• Fast moving mollusks have a closed circulatory
  system using blood vessels

22
Excretion

• Tube shaped nephridia remove ammonia from the
  blood and release it outside the body

23
Response

• Nervous system varies greatly. Other than
  cephalopods, it is very basic. Several ganglia in
  clams and bivalves
• Cephalopods have a highly developed brain and
  nervous system, near equal to vertebrates.

24
Movement

• Some secrete mucus
• Others like the octopus move by jet propulsion

25
Reproduction

• Reproduction is sexual by external fertilization
  as in snails and bivalves
• Some are hermaphroditic like the snail

26
Ancestry of Molluscs
27
Phylum Significance

• Eaten for food by humans and other animals.
  Clams, oysters, scallops, mussels, (shellfish)
  snails (escargot), octopus and squid are popular
  foods
• Research - i.e. snails appear to be cancer free
• Indicators of environmental pollution
• Land snails and slugs damage gardens and crops
• Shipworms destroy wooden boats, docks, and piers.
  
• Filter feeders can concentrate toxins through
  biological magnification (Humans eating them can
  become ill or even die).