C hapter 9 mollusks

Phylum Mollusca

Class: Gastropoda

Class: Bivalvia

Class: Cephalopoda

Class Gastropoda

Snails, Limpets and Slugs

General Body Plan: Gastropod

• Characteristics– 1. Head foot

• Head: sensory nerves, mouth • Foot: attachment and locomotion

General Body Plan: Gastropod

2. Visceral Mass– Organs of

digestion – Circulation – Reproduction – Excretion – Dorsal to the

head foot

General Body Plan: Gastropod

3. Mantle (shell) – Attached to visceral

mass• Encloses most of the

body – Protection

4. Mantle Cavity: – Gas exchange– Elimination of digestive

wastes – Release of reproductive

products

That slimy foot… • Snail Slime:

– Escape– Movement– Water Retention

• Ecological Roles: – Skin regenerating – used in skin beauty products

• http://www.youtube.com/watch?v=JhRwcPRy6l4&safety_mode=true&persist_safety_mode=1&safe=active

Respiration

• One Gill in mantle cavity – Oxygen is taken in – Diffused through the cells

• Open Circulatory System – Pushes blood in to

expand– Pulls it out to contract

• Digestion – Scrape algae– Enzymes break down

food in stomach

• Radula: Scraping mouth – Chitinous belt & curved

teeth • Covers fleshy tongue • Muscles move it back

and forth • Conveyor belt

Torsion

• Benefits – Head enters first:

protection – Operculum seals

opening to prevent drying out

– Allows clean water to enter mantle cavity

– Makes snail more sensitive to stimuli coming from the front

Reproduction

• Monoecious: can be whatever sex they want! – Internal cross

fertilization – One snail acts as

female one acts as male

– Deposit eggs in gelationous strings

Class Bivalvia

Clams, Oysters, Mussles, Scallops

Structure

• Two halves of a shell: Valves – Adductor muscles hold

valves shut • Visceral Mass• Mantel Cavity• Gills • Cilia• Siphon:

– filters water in and out of shell

Foot

– Attach mollusk to surface

– Act as a lure to attract prey

– Surround organs for safety

Ecological Roles

• Edible• Commercial value:

Form Pearls • Valuable in removing

bacteria from polluted water! – Rely on water currents to

get food – Filter in nutrients, filter

out clean water • Valuable food source:

humans, raccoons, otters, birds

Digestive System

• Food comes in through gills – Sorted – Digested – Waste forcibly

pushed out of mantle cavity by valves shutting quickly

Respiratory System

• Respiration: Cilia in gills move water into mantel cavity – Water tubes

exchange water to blood through diffusion

– Water exits bivalve

Human Interaction

• Many, many mollusks are threatened or endangered– Over harvesting– Pollution– Loss of habitat – Loss of water

currents

Mollusks: Cephalopods Octopus, Squid, Cuttlefish

Physical Characteristics

• Anterior– Tentacles and jet

propulsion • Mantle (Shell)

– Nautilus: only cephalopod w external shell

• Fills it with gasses to help w buoyancy

– Squid: internal shell, helps with structure

– Octopus: NO SHELL

Locomotion

• Jet like propulsion out of mantle – Squid: uses it for

catching prey • Up to 25 mph!

– Octopus: escape method

ECOLOGICAL ROLE

• Fierce Predators – Large brains – Complex sensory structures – Rapid locomotion – Grasping tentacles

• http://www.youtube.com/watch?v=p9A-oxUMAy8&safety_mode=true&persist_safety_mode=1&safe=active

Digestion

• Enzymes digest food in stomach– Moves to anus– Expelled during

jet propulsion

Giant Squid Dissection

• http://www.youtube.com/watch?v=d83nSFEoz2A&safety_mode=true&persist_safety_mode=1&safe=active

Predator Adaptations

• Locate prey by sight• capture prey w

tentacles/ suction cups – Tentacles reinforced w

protein

• Eat using a radula – Cuttlefish: small

invertebrates – Octopus:

• Nocturnal: snails, fish, crustations

Predator Adaptations

• Chromatophores – Cells that can change colors

• Tiny muscles contract or expand and chromatophores quickly change color– Alarm response– Defensive – Blend in w environment– Courtship – Bioluminescence

• http://www.youtube.com/watch?v=t-LTWFnGmeg&feature=related&safety_mode=true&persist_safety_mode=1&safe=active