a. bilateral symmetry b. presence of a muscular foot c. mantle formed by dorsal body wall d. true...
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Phylum Mollusca
I. CharacteristicsA. Bilateral SymmetryB. Presence of a muscular footC. Mantle formed by Dorsal Body wallD. True CoelomE. Complex Digestive SystemF. Gas exchange through gills, lungs, mantle, or body
surfaceG. Simple Excretory systemH. Simple nervous system, with true eyes in SOME speciesI. Simpler forms monoecious, more complex forms
dioecious.J. Larval form in all molluscs known as a trochophore
Molluscan Body Plan (general)
II. Class Gastropoda “Stomach footed” Molluscs
examples: Snails, Slugs, Whelks, Conchs, CowriesA. This is the largest and most successful class of MolluscsB. Shell, if present, is singular, and whorled around a common axis known as a columella.C. Right handed shells are dextral; left handed are
sinistral.D. Rasp like Radula used to scrape food.E. Eyes usually positioned on stalks on head.F. Most forms monoeciousG. Torsion occurs as larvae become adults, causing the
organs to lie above the head in the mantle cavity.
A. Dextral shell
C. Sinistral shell
Cross section showing columella
Queen Conch
Pulmonate Land Snail
BananaSlug
MarineCalliostoma
Gastropods – Univalves (1 shell)
Examples - snails, abalone
How to shuck an abalone:http://www.youtube.com/watch?feature=player_detailpage&v=WbEmnfY-niU
Gastropod videos – questions
How is water directed into the mantle cavity?What is the easiest way to tell a slug from a
snail?What is the primary organ of defense for
snails?Nudibranchs are marine gastropods that do
not have a shell. Are these considered snails or slugs?
Gastropods – Secrets of the Sea (pt.1)
http://www.youtube.com/watch?v=z6Z2XCdmEwU
III. Class BivalviaFormerly known as Class Pelecypoda
The “hatchet-footed” molluscs Examples: Clams, Oysters, Scallops, Mussels, cockles,
coquinasA.These organisms all have two shells.B.Bivalves are all sedentary filter feeders.C.Incurrent siphons bring water in, excurrent
siphons take water out.D.Bivalves secrete their shells using nacre, derived
from the compounds in the water.
Bivalves have two siphons for the exchange of nutrients and oxygen into their shells and bodies.
Examples of incurrent and excurrent siphons
Scallop
Giant Clams
Oyster
The Process of Pearl formation:
A . First, a grain of sand or other foreign material gets caught between the shell of the oyster, and the mantle, which is very tender and delicate.
B. Second, the irritant is surrounded by nacre, or mother-of-pearl, to ease the discomfort created by the sharp edges.
C. The oyster continues to secrete nacre until the pearl is formed in a large enough diameter to stop the irritation.
D. Naturally formed pearls are very rare to find, hence their value.
E. Kokichi Mikimoto, the son of a Japanese noodle-maker, was the first to force oysters to form rounded pearls, a process known as culturing. Today, Mikimoto pearls are the most widely sold cultured pearls in the world.
Tahitian Black Pearls
Golden South Sea Pearls from Indonesia $65,000
$12,000
Akoya Japanese Pearls
$24,000
IV. Class Cephalopoda“Head-footed Molluscs”
examples: octopus, squid, cuttlefish, nautilusA. The MOST ADVANCED of all mollusc classes
B. They feed on fishes, other molluscs, crustaceans and wormsC. They have a closed circulatory system – very advancedD. Use funnels for rapid locomotion backwardsE. Octopi are loners and have 8 arms (total = 8)F. Squid are gregarious and have 8 arms and 2 tentacles
(total = 10).G. Both secrete an ink-like substance known as sepia to
confuse their attackers.H. The largest Octopi reach a length of about 3 meters, the
largest squid (Architeuthis) reaches a length of about 60 feet.
I. Water movement in the mantle cavity serves three functions: oxygenation, locomotion, and waste and gamete removal.
Cephalopod vocabulary What cells allow a cephalopod to change color?
Chromatophores The only part of a shell that still exists in squid
Pen (supports the mantle)
Cephalopodshttp://www.youtube.com/watch?feature=player_detailpage&v=Q-jBksy7z8U
Beak -
Camouflaged -
http://www.youtube.com/watch?feature=player_detailpage&v=0GVaa9r1YFohttp://www.youtube.com/watch?v=IznlT8XkmkY&feature=player_embedded#!
Cuttlefish – master of camo 20 minutes later…….
Giant Octopus
Cuttlefish
Chambered Nautilus
Squid
Interesting Facts!
Phylum Mollusca is the second largest phylum, behind only the Phylum
Arthropoda
Most molluscs are found in the ocean
Molluscs are important economically for food and for pearls
The biggest predator of scallops is sea stars!