Zoology

Phylum Mollusk

I. Intro to MollusksA. Mollusk soft bodied

B. 2nd largest phyla

1. small large

2. fast movers slow movers

3. intelligent non-intelligent

4. Deep seas mountain tops

C. Ex: squid, clam, oyster, octopus, snail, slugs, etc.

D. Used as a food source

1. clams, oysters, etc.

E. Used for jewelry (pearls)

F. All have a “foot” specialized muscular organ

II. Cephalopods

A. Facts

1. Cephalo = head / poda = foot

2. Includes…squid, octopus, nautilus

3. Active predators

4. shell nautilus

5. no shell octopus + squid

B. The Nautilus

1. Locomotion-”foot” acts as a siphon pushes water out-gas filled chambers

2. Nervous System-intelligent-chemoreceptor cell used to camouflage

3. Others-60 to 90 tentacles (no suckers)-sexual reproduction-radula tongue like structure

i. 250,000 teeth ii. Conveyor belt

C. The Squid

1. Locomotion-same as nautilus

2. Nervous System-exceptional eyes-chemoreceptor cell

3. Others-sepia ink sac; helps hide

from enemies-8 arms / 2 tentacles-pen acts as backbone of

squid-beak – used to break up food

D. The Octopus

1. Locomotion – same as squid2. Nervous System

-great eye sight-extremely intelligent (can be conditioned)-chemoreceptor cells

3. Others-sepia -pen-8 arms – all with suction cups-beak – used to break up food

III. GastropodsA. Facts

1. gaster = stomach / poda = foot2. Largest group of mollusks (50,000)3. Ex: snails and slugs4. Dioecious (individual sexes) or

monoecious (both sexes)5. can be terrestrial (gills or lungs)6. Sluggish or slow moving7. Usually feed on algae or plankton8. Occupy a shell for protection

B. Conus

1. active predator

2. uses worm-like tongue to lure in prey

-fish bites…proboscis fires…injects venom…paralyzes fish

3. lethal sting to humans

IV. Class Pelecypoda (Bivalves)

A. Facts

1. pelecy = hatchet / poda = foot

2. Ex: mussels, clams, scallops, oysters

3. Filter Feeders

4. no radula

5. Dioecious

B. The Clam

1. External Anatomy

a. Umbo – oldest part of the shell

b. Hinge Ligament – keeps the 2 shells connected

c. Growth Rings

Growth Rings1.

2. Umbo

Anterior Side

Ventral Side

3. Hinge Ligament

2. Internal Anatomy

a. Siphons

-incurrent takes water + food into clam

-excurrent removes waste

b. Mantle – tissue that covers the organs of the clam

-similar to skin

c. Palp – guide food into the mouth

d. Heart

-3 chambered

-beats slow (0.2 – 30 times/min.)

e. Kidneys

-filter blood

-U shaped

-Nephridial Tubules – connect to the kidney

f. Ganglia

-3 pairs

-poorly developed

g. Muscles

-anterior adductor

-posterior adductor

-both close the shell

-Extremely strong