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Phylum Mollusca. Class Gastropoda. Class Gastropoda. Defining characteristics Visceral mass and nervous system become twisted 90-180 ° during embryonic development Proteinaceous shield on the foot (operculum). Gastropod Morphology and Movement.

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phylum mollusca

Phylum Mollusca

Class Gastropoda

Gastropods

class gastropoda
Class Gastropoda
  • Defining characteristics
    • Visceral mass and nervous system become twisted 90-180° during embryonic development
    • Proteinaceous shield on the foot (operculum)

Gastropods

gastropod morphology and movement
Gastropod Morphology and Movement
  • The typical snail consists of a visceral mass, which sits atop a muscular foot
    • The visceral mass is protected by a univalve shell that is coiled

Gastropods

dextral and sinistral coiling
Dextral and Sinistral Coiling
  • The shell is usually carried on the left side of the body and coils to the right (dextral)
  • Few species are sinistral
    • Shell coils to the left (lightning whelk)

Gastropods

torsion
Torsion

Gastropods

subclass prosobranchia
Subclass Prosobranchia
  • Defining characteristic
    • Mantle cavity generally anterior due to torsion
    • Usually have protective shells
  • Includes most marine gastropods

Oyster Drills

Gastropods

prosobranchia anatomy
Prosobranchia Anatomy
  • Molluscan gill
    • Ctenidium, consists of a series of flattened, triangular sheets
    • Water is drawn into the animal by gill cilia
    • Osphradium

Gastropods

reproduction

Veliger

Trochophore

Reproduction
  • Life begins as a trochophore larvae which then develops into a veliger larvae
    • The veliger is where most of the organ systems develop
    • During development the process of torsion begins

Gastropods

local representatives
Local Representatives
  • Banded Tulip (Fasciolaria tulipa)
  • Knobbed Whelk (Busycon carica)

True & Banded Tulip

Gastropods

subclass opisthobranchia
Subclass Opisthobranchia
  • Defining characteristic
    • Mantle cavity located posteriorly due to detorsion
    • Sea slugs and sea hares

Gastropods

nudibranchs sea slugs sea hares
Nudibranchs, Sea slugs, & Sea hares
  • A radula and foot for creeping is usually present (sea slugs)
  • Some have parapodia used for swimming
  • Well developed head and sensory tentacles

Anemone Sea Slug

Gastropods

lemon nudibranch
Lemon Nudibranch

Nudibranchs have no shell or mantle cavity

Lack gills, instead have respiratory projections on the dorsal surface

Gastropods

subclass comparisons
Subclass comparisons
  • Different from prosobranchia:
    • Reduction or loss of the shell and operculum
    • Limited torsion
    • Reduction or loss of the mantle cavity
    • Reduction or loss of ctenida
    • Many have evolved different respiratory structures which are unrelated to ctenidia

Gastropods

local species
Local species
  • Sooty sea hare (Aplysia brasiliana)
    • Have large swimming parapodia and a greatly reduced shell on the back

Gastropods