Phylum
Mollusca
(5 Classes)
Policemen censor gals in scant bikinis!
Polyplacophora – Many plates on a foot
Cephalopoda – Head foot
Gastropoda – Stomach
Scaphopoda – Tusk shell
Bivalvia – Hatchet foot
foot
Typical questions for Mollusca
How many of these specimens posses a radula?
Which ones are filter feeders?
Which have undergone torsion? Detorsion?
What is the function of the mantle?
Name a class used for currency
Which specimens lungs vs. gills?
have think of which live on land vs. in water……
Oldest part of a univalve shell? Bivalve?
Just
Answers…maybe
• Gastropods, Cephalopoda, Mono-, A- & Polyplacophora
• Bivalvia (Scaphopoda….have a captacula)
• Gastropods Opisthobranchia (sea hares & sea slugs)
and the land slugs of the Pulmonata
• Mantle secretes the shell
• Scaphopoda
• Pulmonata – their name gives this away
• Apex for Univalve, Umbo for bivalve but often the terms
are used interchangeably
Anus
Mantle
Radula
in
mouth
Gills in
mantle
cavity
Head
Chitons radula, 8 plates
Class
Polyplacophora
My tentacles (2) & arms are derived
from the Gastropod foot
Cephalopoda - Octopuses, Squid, Nautilus,
Cuttlefish…beak, pen, ink sac, chromatophores,
jet propulsion……….dissection.
Class
Apex
Prosobranchia
Aquatic –marine.
Generally they have thick
pointed shells, with
spines. Many have
opercula.
Subclass
Gastropoda
WORDS TO KNOW:
snails, conchs,
torsion, coiling,
radula,
operculum &
egg sac
Subclass
Pulmonata
Aquatic –freshwater. Shells are
thin, rounded, with no spines, and
have no opercula.
Pulmonata
Slug
Subclass
Detorsion…
If something
looks strange,
chances are….
…….it is
something from
Class Gastropoda
(…or your
roommate!)
Subclass
Opisthobranchia
Nudibranch
This is correct!
Class Gastropoda
Sinistral
‘POP’
Subclass Prosobranchia
- Aquatic snails (“shells”)
- Have gills
Subclass Opisthobranchia
- Marine
- Have gills
- Nudibranchs / Sea slugs / Sea hares
- Mantle cavity & shell reduced or absent
Subclass Pulmonata
- Terrestrial Slugs and terrestrial snails
- Have lungs
Dextral
Class
Scaphopoda - “tusk shells”
Currency for Wampum Indians. Head in sand.
Respire through mantle (no gills.)
Captacula for feeding on foramniferans
Name of
oldest
part?
D
A
ClaBivalvia
V
P
or Pelecypoda - clams, scallops etc.
filter feeders, bivalved shells…… dissection
Umbo
D
A
ClaBivalvia
V
P
or Pelecypoda - clams, scallops etc.
filter feeders, bivalved shells…… dissection
Dorsal (hinge)
Path of water (O2)
Heart Ventricle
Auricle
Bulbus arteriosus
Anterior
(Umbo)
Adductor
muscles
Area of gastric
& /digestive
glands
Gills
Mouth
Foot
Gills or
ctenidium –
Each = 2
demibranchs
Visceral
Mass
Excurrent
& Incurrent
siphon –
(hairs &
papullae)
Mantle
Ventral
Posterior
(siphons)
Schematic Diag. of
a Clam Dissection
Very