Mollusca

Marine Science

Module 4 ~ Unit 4

Mollusca

• Mollusk characteristics overview

• Characteristic differences

• Assignment 4.4.1

• Classes: Bivalves, Gastropods, and Cephalopods

• Other Classes

• Assignment 4.4.2

Characteristics Overview

• Cephalization: (Has a definite head/nervous system)

• Body cavity has definitive digestive/intestinal system• Has an excretory system with kidney or

nephridium (tube-like organ) • Open circulatory system with heart

• Gills for respiration• Muscular foot used for movement• Some have protective shell over soft body

Which ones are mollusks?

They all look so different!How can they all be

mollusks?

Differences of Characteristics

• Cephalization• “Head” means they have

eyes, mouth, and a brain… not necessarily the way we might imagine a head looking

Differences of Characteristics

• Most mollusks have a radula (like a cat’s tongue)

Fresh water pond snail cleaning algae off glass.

Radula of squid

Differences of Characteristics

• Most have a muscular foot for movement– When you eat clams and scallops you’re eating the foot

Differences of Characteristics

• She sold sea shells by the sea shore.

• Some mollusks have a two part shell, some only one, and some don’t use shells on the outside

Any questions so

far?

Bivalves ~ Gastropods ~ Cephalopods

• Bi (two) valves– Don’t have radula… they filter feed– Giant Killer Clams

• Gastro (stomach) pods (foot)– a.k.a. snails and slugs– Nudibranchs

• Cephalo (head) pods (foot)– Don’t have shells (exception is the Nautilus)

• More on these in a moment…

Bivalves ~ Gastropods ~ Cephalopods

Assignment 4.1.1

• Create a PowerPoint presentation that identifies and illustrates the various characteristics of mollusks.

• Include habitat, what they feed on and examples and specific explanations of the three groups of mollusks.

• Your presentation must be no longer than 7 slides.

• Make sure you give credit for any graphics that are not your own. Include a reference list at the end.

• You should have at least 3 credible reference sites. Contact your instructor to discuss what a "credible reference site" is. (REQUIRED CONTACT).

Mollusca

Marine Science

Module 4 ~ Unit 4

..Continued..

Pelecypoda

Pelecypoda

• A.K.A. the bivalve class

• 2 shell halves• Filter feeders (no radula)• Shell secreted by the mantle• Have 2 siphons for pulling in & pushing out water

• Some have eyes (scallops)

Pop Quiz

How many siphons does a bivalve have?

Clam buries itself: http://www.youtube.com/watch?v=mWs-zAd1avM&feature=related

Gastropoda

• A.K.A. abalones, snails, and slugs

• One shell with an operculum (door)

• Has head with eyes and radula• One group does not have shell (nudibranchs)

• Gastropod fossil link from Angel– http://www.oum.ox.ac.uk/thezone/fossils/inverts/gastro.htm

Which of the following mollusks are not part of the gastropoda class?

SnailsSquids

AbalonesSlugs

Conch

Cephalopoda

• A.K.A. squid, octopus, nautilus

• Only the nautilus has an external shell

• Octopus and squid have 8 tentacles (squid and cuttlefish have 2 additional longer tentacles)

• Well-developed eyes and brain

Octopuses or Octopi?Many people get confused about the proper plural for the word octopus. Octopus is frequently given a Latin plural, yet the word derives its second root from Greek, not Latin (the english "foot" root from Latin is "pod" or "ped", while from Greek it is "pus"). What is the proper plural, anyway? Many say "octopi." The singular looks like a Latin masculine singular, ending in "us," but it really isn't, so pluralizing it to "octopi" is not correct. Most people also mispronounce it as well. If it were "octopi," it would be pronounced "octo-pee" not "octo-pie," and that sounds silly! So, the correct plural is "octopuses," believe it or not. I prefer not to use either of them. Every time you say "octopuses" someone will correct you, and you end up in an argument. So I like to use "octopods," which is the proper plural of the taxonomic order Octopoda, containing the eight-armed cephalopods.

Pelecypoda

Polyplacophora (chitons)- 8-plated shell

Monoplacophora

Scaphopoda- A.K.A. tusk shells

Any questions?

Assignment 4.4.2• Part 1: Prepare a chart that compares and

contrasts all groups of mollusks. Your chart should cover all the 7 characteristics of mollusks, as well as provide a list of common named species for each group. Include habitat and feeding strategies for each group.

• Part 2: Choose one organism from each group of mollusk that you find interesting. Prepare a fact sheet for each organism. The fact sheet should include as much detail as possible related to the critter. Graphics (i.e., pictures of critter and habitat, relationships with other critters, drawings of lifecycle and/or anatomy, etc. ) will enhance your fact sheet.

See Characteristics OverviewSlide in the beginning for 7 characteristics