PhylumPhylumMolluscaMollusca

Chapter 13 Part 1 of 3Chapter 13 Part 1 of 3

General CharacteristicsGeneral Characteristics Unsegmented Unsegmented Soft Soft bodied critters - Bilateral symmetrybodied critters - Bilateral symmetry Shell formed by Shell formed by mantlemantle secretions secretions Body often protected by a valve (shell)Body often protected by a valve (shell) DioeciousDioecious (Greek for “two households”) separate sexes (Greek for “two households”) separate sexes Aquatic & Terrestrial life stylesAquatic & Terrestrial life styles Complete digestive systemComplete digestive system Open Circulatory System (gastropods & Bivalves)Open Circulatory System (gastropods & Bivalves) Closed Circulation in cephlapodsClosed Circulation in cephlapods

ClassificationClassification Based on presence or absence of a shell (valve), Based on presence or absence of a shell (valve),

the number of shells and by the type of foot the number of shells and by the type of foot presentpresent

Class Class GastropodaGastropoda - - ““stomach footstomach foot” ” one valve: one valve: snails, slugs, abalone, nudibranchs.snails, slugs, abalone, nudibranchs.

Class Class BivalviaBivalvia – “– “two folding doorstwo folding doors”” - - clams, clams, scallops, mussels, oystersscallops, mussels, oysters

Class Class CephalopodaCephalopoda - “- “Head-footHead-foot” – ” – squid, squid, octopus, cuttlefish, nautilusoctopus, cuttlefish, nautilus

Class Class GastropodaGastropoda snails, slugs, abalone, nudibranchs.snails, slugs, abalone, nudibranchs.

““stomach footstomach foot”– ”– most have one valve, some w/outmost have one valve, some w/out Feed w/ “cat-tongue-like” radulaFeed w/ “cat-tongue-like” radula Movement by creeping on a single foot.Movement by creeping on a single foot. Complete digestion, open circulationComplete digestion, open circulation A tight fitting plate (A tight fitting plate ( operculum operculum) attached to the foot that can be closed ) attached to the foot that can be closed

tight to protect the animal, a “trap door”tight to protect the animal, a “trap door”

Class Class BivalviaBivalvia clams, scallops, mussels, oysters,clams, scallops, mussels, oysters, ““two folding doorstwo folding doors” – ” – 2 shells secreted by the mantle2 shells secreted by the mantle On some, edges of mantle w/ sensory tentacles & eye spotsOn some, edges of mantle w/ sensory tentacles & eye spots Muscular footMuscular foot Most are filter feeders – no radulaMost are filter feeders – no radula Complete digestion, open circulationComplete digestion, open circulation We are dissecting clams….We are dissecting clams….

Oyster w/ pearl

Clam DissectedClam Dissected1. Valve2. Anterior3. Posterior4. Dorsal5. Ventral6. Umbo

Class Class CephalopodaCephalopoda Squid, octopus, cuttlefish, nautilusSquid, octopus, cuttlefish, nautilus ““Head-footHead-foot” – ” – shell extremely modified or even shell extremely modified or even

absentabsent Most intelligent of all invertebratesMost intelligent of all invertebrates.. Well developed vision ( best of all invertebrates)Well developed vision ( best of all invertebrates) All w/ arms & or tentaclesAll w/ arms & or tentacles All are Predators. All are marineAll are Predators. All are marine

Octopus – no shell present – foot modified into 8 armsOctopus – no shell present – foot modified into 8 arms Squid – we’ll be dissecting squid, shell modified into flexible Squid – we’ll be dissecting squid, shell modified into flexible

internal “pen”internal “pen” Cuttlefish – internal hard shell (used by parakeet owners)Cuttlefish – internal hard shell (used by parakeet owners) Nautilus – external shell many tentaclesNautilus – external shell many tentacles

CephalopodsCephalopodsSee the octopus?

Squid DissectionSquid DissectionTrunkNeckHeadMantleFinTentacleArmSiphonEye

sucker, teeth, stalk

Squid DissectionSquid Dissection

Try to identify: Arms, Tentacle, Eye, Siphon, Fin and Sucker

All Done w/ the MollusksAll Done w/ the Mollusks