BY255L - Invertebrate Zoology Lab - Mollusca (pronounce)

Notes

Note that mollusks are triploblastic (have an epidermis, mesodermis and endodermis). Muscles develop from the mesoderm layer. Muscles make complex predatory behaviors possible.

Review Gastropods Revisited handout
(Know all information on the cards, as usual)

First Mollusk lab
Review Gastropods Revisited handout
(Know all information on the cards, as usual)

Class Polyplacophora (chitons)
Class Gastropoda "stomach foot" (snails)
- Subclass Pulmonata
Class Bivalvia (or Pelecypoda "ax-foot")
Class Cephalopoda "head-foot"
Class Aplacophora "without covering plate" (solenogasters)
Class Monoplacophora (<20 species)
Class Scaphopoda "shovel foot" (tusk shells)
Mollusca Web links

Class Polyplacophora (chitons)

Not truly serialized despite repetition of plates.
Tolerate harsh conditions by clinging tightly to substrate, especially predation and dessication during low tide.
Katharina tunicata (black chiton) views and links
Mopalia muscosa (mossy chiton)

Class Gastropoda "stomach foot" (snails)

These cephalized mollusks usually have tentacles and simple eyes. Visceral mass is twisted (torsion). Operculum is present in more primitive species.

Typical Gastropod veliger of Crepidula fornicata (slipper shell)

Subclass Prosobranchia

Organization of Typical Prosobranchia Gastropod (Cal State Long Beach)

Prosobranchia orders

Order Archaegastropoda has bipectinate gills
Order Mesogastropoda has monopectinate gills
Order Neogastropoda have monopectinate gills with siphon and siphonal canal

Order Archaegastropoda has bipectinate gills

Order Mesogastropoda has monopectinate gills

Order Neogastropoda have monopectinate gills with siphon and siphonal canal

Subclass Opisthobranchia (pronounce)

sea slugs and nudibranches
Opisthobranchs have no shell or an internal shell.
They appear bilaterally symmetrical because there is no torsion.
The mantle cavity is missing or on the right side.
Nudibranch (pronounce)
Sea hare

Subclass Pulmonata

Gills are absent.
These are mostly terrestrial species with a modified mantle cavity that forms a "lung" (a pneumostome).
Limax sp. (garden slug)
Helix sp. (snail)
Snail radula micrograph

(Additional Notes for Lab 2)

*Phylum Mollusca Review of mollusk characteristics from last week

Class Bivalvia (or Pelecypoda "ax-foot")

Two shells (valves) hinged together
Laterally compressed shell
No head
Many have a digging foot
Review external shell esp. umbo oldest part of shell and dorsal, ventral, anterior posterior
Right and left valves
For dissection - shells should already be opened
Cut through the ligament with a single edge razor and pry apart
Internal anatomy overhead page 138
Review structures - umbo, teeth, foot, gills, anterior and posterior adductor muscles and mantle
Aequipecten sp. (scallop)
Cockle shell
Donax variabilis (coquinas)
Venus mercenaria (hard-shell clam)
Clam shell cross section
Teredo sp. (wood-boring clam) Shipworms have been making a comeback along norther U.S. coasts and in other climes that have been either too cool or, ironically, too polluted for the animals. Since the Clean Water Act of 1972, wooden pilings that had been in the water 100 years began to fall down

Class Cephalopoda "head-foot"

Well-developed brain and central nervous system muscular arms and tentacles around mouth,
beak-like jaws
jet propulsion by taking water into mantle cavity
Four orders: Squids (Loligo), cuttlefish, octopus, nautilus
For dissection - single longitudinal cut through the ventral mantle
Make a shallow, then a deeper cut, the mantle is very thick.
Overhead of internal anatomy page 144
Review structures - siphon, articulating ridge, rectum and ink sac gills and branchial hearts and pen
Loligo sp. (squid)
Nautilus pompilius (chambered nautilus)
Nautiloid fossil (Eocene 54.8-33.7 mya)
Sepia officinalis (cuttlefish)

BY255L - Invertebrate Zoology Lab - Mollusca (pronounce)

Notes

Contents

Class Polyplacophora (chitons)

Class Gastropoda "stomach foot" (snails)

Subclass Prosobranchia

Organization of Typical Prosobranchia Gastropod (Cal State Long Beach)

Prosobranchia orders

Order Archaegastropoda has bipectinate gills

Order Mesogastropoda has monopectinate gills

Order Neogastropoda have monopectinate gills with siphon and siphonal canal

Subclass Opisthobranchia (pronounce)

Subclass Pulmonata

(Additional Notes for Lab 2)

Class Bivalvia (or Pelecypoda "ax-foot")

Class Cephalopoda "head-foot"

Class Aplacophora "without covering plate" (solenogasters)

Class Monoplacophora (<20 species)

Class Scaphopoda "shovel foot" (tusk shells)

Mollusca Web links

General Web links

Cephalopoda links

Gastropoda links

Bivalvia links