PHYLUM MOLLUSCA Soft bodied Triploblastic

Mouth and Anus True Coelum

Bilaterally symmetrical Moist environments

http://infusion.allconet.org/webquest/PhylumMollusca.html

Mollusca

• Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids

• Most molluscs are marine, though some inhabit fresh water and some are terrestrial

• Molluscs are soft-bodied animals, most are protected by a hard shell

• Most molluscs have separate sexes with gonads located in the visceral mass

• Most have kidneys – metanephridia

Fig. 33-15

Nephridium Visceral mass

Coelom

Mantle

Mantle cavity

Heart

Intestine

Gonads

Stomach

Shell

Radula

Mouth Esophagus Nerve

cords Foot

Gill

Anus

Mouth

Radula

Three main parts that all Mollusca have: Muscular foot, a Visceral mass and a Mantle

Most also have a water-filled mantle cavity, and feed using a rasplike radula

Mollusca: Polyplacophora

Class Polyplacophora consists of the chitons, oval-shaped marine animals encased in an armor of eight dorsal plates

Marine only

Mollusca: Gastropods

About three-quarters of all living species of molluscs are gastropods

(b) sea slug (a) land snail

Most gastropods are marine, but many are freshwater and terrestrial species

Most have a single, spiraled shell

Slugs lack a shell or have a reduced shell

Mollusca: Gastropods

Banana slug courtship Each almost 10 inches long!

Fig. 33-18

Mouth

Anus

Mantle cavity

Stomach Intestine

The most distinctive characteristic of gastropods is torsion, which causes the animal’s anus and mantle to end up above its head

Mollusca: Bivalves •Molluscs of class Bivalvia include many species of clams, oysters, mussels, and scallops

•They have a shell divided into two halves

•The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange

Umbo The oldest part of the shell

ridges show where mantle has laid down shell

Class Bivalvia - Anatomy

anus

intestine

Labial Palps

Mouth

gills

Siphon

Foot

Zebra Mussels: Dreissena polymorpha

Native to Asia, introduced to the North America in

ballast water

Mollusca: Cephalopods

Class Cephalopoda includes squids, octopuses, nautiluses and the extinct ammonites

Cephalopods have a closed circulatory system, well-developed sense organs, and a complex brain

Most octopuses creep along the sea floor in search of prey

Octopus

Squids use their siphon to fire a jet of water, which allows them to swim very quickly

Mollusca: Cephalopods

Mollusca: Cephalopods

One small group of shelled cephalopods, the nautiluses, survives today

Chambered nautilus

Mollusca: Giant Squid

Monsters of the deep….

Colossal Squid

http://squid.tepapa.govt.nz/anatomy/article/the-body-of-the-colossal-squid

Paul the octopus “There was something

about the way he looked at our visitors when they came close to the tank. It was so unusual, so we tried to find out what his special talents were”

Paul the Octopus predicts world winners

http://goal.blogs.nytimes.com/2010/10/26/paul-the-octopus-who-predicted-world-cup-matches-dies/

Expectations for Mollusca – Lab 9 • Go through Lab 9 in your lab book, identify all of

the body parts and answer all of the questions.

• What are the key characteristics of each class of mollusca?

• Differentiate between the Gastropoda, Bivalvia and Cephalopoda.

• For this one, no quiz, just answer all of the lab book questions and show me your dissection prior to finishing!