Mollusks
Phylum Mollusca
Advanced Invertebrates
• Phylum Mollusca Characteristics
– 1. Visceral Mass: soft bodied portion
containing internal organs
– 2. Foot: Strong muscular part used for
locomotion
– 3. Mantle: Covering enveloping the visceral
mass
• Over 112,000 different species
Class Gastropoda
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“Belly Foot”
Snails
Slugs
Conches
Class Cephalopoda
• “Head Foot”
• Octopus
• Squid
Class Bivalvia
• Clams
• Oysters
• Scallops
Classification
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Common Name: Clam
Scientific Name: Unio, Anodonta
Phylum: Mollusca
Class: Bivalvia
Other: Class Pelecypoda “Hatchet Foot”
Major Characteristics
• Body Plan: Foot, Mantle, Visceral Mass
• Body Cavity: Visceral Mass contains all
internal organs
• Symmetry: Bilateral
• Cell Specialization: Complex Organs,
“Soft Bodied”
Life Support Processes
• Absorption: Intestines, Nephridia
• Feeding: Filter Feeder, Gills, Radula =
flexible, tongue-like projection with teeth
• Digestion: Stomach, Intestines
• Respiration: Gills
• Circulation: Open System - Blood travels
through sinuses, flows into pericardial
cavity around heart, blood pigment is blue
Hemocyanin
Life Support Processes
• Excretion: Anus = solids, Nephridia =
remove liquid ammonia waste
• Secretion: The mantle secretes the shell
• Response: Ganglia, Ocelli (Primitive
Eyespot), Statocysts = Balance
• Movement: Foot = burrow into ocean
floor, Adductor Muscles = Opens shell
when relaxed
Life Support Processes
• Reproduction: Separate sexes,
Trochophore = larvae
• Support: Shell provides all protection
Ecological Relationships
• Sessile
• Pearl Formation = due to secretion of
mantle
• Food for starfish
Body Systems Compared With
Humans
• Digestive System
• Separate sexes
• Gonads
Advancements Over Previous
Phylum
• Heart
• Gills
• Shell
• The largest bivalve is the Marine Giant
Clam that can reach a size of 50 in. in
length and can weigh over 750 lbs.!
• The slowest growing animal of any kind is a
deep sea clam which only grows .31 in
every 100 years!
• The largest known invertebrate is the Giant
Squid Architeuthis dux. They can be over
60 ft. in length and weigh more than 4,000
lbs.!
• The largest eye in the animal kingdom
belongs to the Giant Squid; over 16 in. in
diameter! (About the size of a hubcap)