Station

1
Station 8Class Polyplacophoramany plate
bearers

• Ex Chitons
• 8 overlapping plates in shell use a foot to
  creep along

2
Station 9 Class Scaphopodahollow or
boat-shaped foot

• Commonly called tusk shells or tooth shells
• Tubular shell open at both ends with creeping
  foot used to burrow into mud or sand
• Found in subtital zone over 6000m in depth

3
Station 10Class Gastropodastomach foot

• Stomach-footed mollusk
• Largest, most successful group ?
• Ex Snails, Slugs, Conchs, Sea Slugs
• Most of these animals are usually sluggish
  because of a heavy shell
• Torsion moves mantle cavity to front of body
  and twists organs in 180 degree rotation occurs
  in veliger stage
• Advantage allows head to be drawn into shell
  for protection
• Disadvantage fouling (anus in a position to
  drop wastes on head and in front of gills ugh
  ?)
• Adaptations to avoid fouling
• Loss of right gill
• Elongated siphon
• Wastes expelled forcibly with air or water from
  lung
• Copy Figure 16-13 in your book!

4
Station 11Class Gastropoda Continued

• Univalve one shell animal snail
• Feeding algae, plankton, scavenger, carnivorous
  
• FYI you do not need to write this part
• Members of the genus Conus eject toxins from
  their radula
• A snail may feed continuously for hours or days
  tearing away an oysters shell and flesh

5
Station 12Class Gastropoda Continued

• Respiration
• Gills
• Skin of mantle
• Nervous 3 pairs of ganglia act as brain
• Eyes
• Statocysts on end of tentacles balance
• Tactile organs on end of tentacles touch

6
Station 13Class Gastropoda Continued

• Reproduction most are monoecious (may be
  dioecious depending on species) do you remember
  what those terms mean?
• Snails
• 1. Courtship use love darts to induce mating
• Eject a dart from a dart sac (figure 16-18) into
  the partners body to initiate reproduction.
  Some researchers believe it increases storage of
  sperm from the dart shooter sometimes for years
  after copulation insuring that the initial
  shooter fathers more offspring than future
  partners.
• 2. Exchange of spermatophore (packets of sperm)
• 3. Fertilized eggs from each snail are slowly
  deposited singly or in a jelly-like mass in a
  moist, dark area, where each zygote slowly
  develops and hatches into a tiny snail-complete
  with an even tinier and transparent shell of its
  own.

7
Station 14Subclasses of Gastropods

• Prosobranchia- marine snails, some freshwater
  snails, and terrestrial gastropods
• Opisthobranchia nearly all marine (sea slugs,
  sea butterflies) live in shallow water
• Techtibranch Gastropod with gills and shell
• Nudibranch Gastropod with no shell or gill
• Palmonta land snails some freshwater snails,
  they have a lung

8
Station 15 Class Bilvalviatwo shells

• Used to be called Pelecypoda means
  hatchet-footed
• Examples Mussels, clams, scallops, oysters, ship
  worms

9
Station 16Class Bivalvia Continued

• Shell 2 valves held together by hinge ligament
  on dorsal side open/close by 2 adductor muscles
• Mantle posterior edges modified to form
  incurrent and ex-current siphons to regulate
  water flow in and out of shell
• Pearl formation a grain of sand gets trapped
  between mantle and nacre mantle secrets macre
  (mucus) around it to prevent irritation. The
  material solidifies to make the pearl!
• Locomotion foot except scallops which squirt
  water from their shell to move through the water

10
Station 17Class Bivalvia Continued

• Feeding filter feeder secrete mucus over
  gills food is trapped as water flows over gills,
  mucus transferred to mouth
• Nervous
• few species have eyes with cornea, lens, and
  retina at edge of shell others have OCELLI
  (eyespots) which are sensitive to light
• nerve cord
• statocysts
• chemoreceptors
• tactile receptors

11
Station 18Class Bivalves Continued

• Reproduction dioecious eggs are fertilized in
  water
• Marine Species egg hatches into trochophore
  then develop to veliger then to spat and finally
  adult
• Freshwater Species eggs fertilized in shell
  egg to zygote to glochidium (parasite on fish
  gills) to adult