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Transcript
Cuttlefish
Snail
Nudibranch
Chapter 16
Molluscs
Scallop
Limpet
Protostomes that shed their exoskeleton
Protostomes with spiral embryonic cleavage
Anatomy of a Generalized Mollusc
Mantle: The dorsal body wall that often extends
beyond the visceral mass, often secretes calcium
carbonate, forming a shell.
Radula: A toothed chitinous ribbon used for scraping
up food into the mouth. Unique to all molluscs
except bivalves.
Visceral Mass: Dorsal concentration of internal
organs.
Gills: A large surface-area tissue used for exchanging
gases. Found in molluscs with open or closed
circulatory systems.
Anatomy of a Generalized Mollusc
Circulatory Systems
Closed Circulatory System: Blood is entirely
contained within blood vessels. Efficient. Uses a
pumping heart, vessels, and capillaries. Found in
cephalopods.
Circulatory Systems
Open Circulatory System: Blood is not entirely
contained within blood vessels, rather it flows in
vessels in some parts of the body, but opens into
sinuses in other parts. Less efficient. Still uses a
pumping heart and vessels. Found in other molluscs.
Mollusk Descriptions
Baldomero Olivera is a Distinguished Professor of Biology at the University
of Utah. He is also an Adjunct Professor at the Salk Institute, La Jolla,
California and at the Marine Science Institute, University of the Philippines.
Bivalves
• Mussels, clams,
scallops and oysters
• No head, no radula
• Filter feeders
• Some use their foot
to pull themselves
along, scallops move
by jet propulsion via
“clapping”
Gastropods
• > 70,000 species of
snails, conchs, whelks,
slugs and sea hares
• Large, flat foot for
movement, one or
two gills
• Use shell for selfdefense, but some
species have lost it
• Most are herbivorous
or scavengers
Cephalopods
• Squid, cuttlefish,
nautilus, octopus
• Well developed
eyes, shell often
absent
• Foot modified into
a siphon
• Diocious
• Complex,
advanced brain
Predator Molluscs
Nova Cone Snail Video
35:20-42:40
Modern cephalopods just tip over and swim with the ancestral dorsal
surface pointing in the direction that they travel. The result; the
morphological anterior side is functionally dorsal, the morphological
posterior is functionally ventral.
The mouth and arms are now ventral, but it swims “up” (the new
anterior).
Anterior
Ventral
Dorsal
Posterior
Motion
Squid Dissection