Phylum Mollusca

-2nd most successful animal phylum behind the arthropods.

-Enormous range of size, colors, lifestyles, mythologies.

-Very important to the human race due to ease of capture, large numbers, edibility, shells, beauty.

Phylum Mollusca*We will show examples of 3 different classes for each characteristic*

1) Class gastropoda (snails and slugs)

2) Class cephalopoda1) (squid/cuttlefish)

3) Class bivalvia(clams and oysters)

Phylum Mollusca1) Bilateral symmetry – body can be separated into two even parts down the middle.

Cut in half

Phylum Mollusca2) Mantle – muscular “bag” used to pump/circulate water throughout body.

*Used for feeding, respiration, or jet propulsion

Phylum Mollusca3) Musucular foot – exactly what it sounds like

**Some use it for movement, others for predation/self-defense

Phylum Mollusca4) Radula – This is like the tongue of the animal, but sharpened and jagged instead of soft. Gastropoda

Phylum MolluscaRadula - Cephalopoda

Phylum MolluscaRadula - bivalvia

Bivalves lack a significant hard radula because they have no use for it, most are filter feeders who sit and wait for their food.

Instead, most have evolved a crystalline style to mash up food. Sort of like a giant tooth in the stomach (mortar and pestle).

*Very few still have a small radula to scrape food.

Phylum Mollusca5) Develeopment – trochophore and veliger stages

SquidClass Cephalopoda

-Unlike other mollusks, cephalopods have little to no shell.*Squid have a very thin bar that runs down the center of their interior.

-Siphon water in and out of mantle to move around (jet propulsion)

Squid-A common misconception is that squid have 10 tentacles and octopi have 8.

-The truth is that octopi have 8 ARMS, and squid have 8 ARMS and 2 TENTACLES.

*The arms of both organisms have suction cups.

*Some are jagged some are soft.

*Some squid have hooks on their 2 tentacles.

Drawing 1 ExteriorLay your

specimen out on your tray with

arms and tentacles

stretched. Locate and label the

circled terms in your drawing

Carefully cut up the mantle of the squid, leaving as

much of the interior intact as possible. Locate and

label the circled terms in the picture. DO

NOT CUT THROUGH

THE FUNNEL.

Attempt to remove the “pen” (shell) inside the mantle without breaking it.

Drawing 2 – Digestive/respiratory This gives you a clean view of all of the internal organs and where they enter/exit the body.

DRAWING 3- MOUTH PARTS-Buccal Mass-Esophagus-Radula (beak)

Drawing 4 – radula (beak)• Remove the beak and clean it off as much as

possible (The muscle you are removing is called the buccal mass).

• Use the dissecting scope to take a closer look at the radula and a tentacle up close. Draw them both.

Questions:

• Name 2 functions of the squid’s mantle. • Describe the “shell” of a squid.• Name 2 parts of the squid anatomy that the

mussel (tomorrows dissection) will also have.