InvertebatesMolluscs

Ch. 7

Objectives

Body Structure

• phylum Mollusca• More species in ocean

than any other animal group (over 200,000)

• Soft body in a calcium carbonate shell – Many variations on this

• Mantle– Thin layer of tissue that

secretes shell

Body Type• Foot

– Muscular, used to move• Radula

– Unique to molluscs– Made of chitin– Ribbon of small teeth

Blood Sucker!

• Cooper’s nutmeg snail prey on electric rays

• Extends its long proboscis

• Makes a tiny cut in the rays skin with its radula

• Sucks the blood out

Types of Molluscs: Gastropods

• Largest, most common, and most varied group

• 75,000 + species, mostly marine

• Snails, limpets, abalones, nudibranchs

Limpet with barnacles

Nudibranchs

• Huge variety—3000 + species

• Blind• Prey on stinging creatures• Store prey’s sting and

recycle it in their own defense through feather plumes (also gills)

• Lifespan is several weeks• hermaphrodites

Types of Molluscs: Bivalves

• Clams, mussels, oysters, and more

• Two valves, or shells• Filter out small food

particles from the water

Abalone

Giant Clam, Palau

Oysters and Pearls

• Oyster secretes layers of calcium carbonate to coat irritating particles or parasites in the mantle

• Cultured pearls are obtained by inserting a tiny bit of shell or plastic into the mantle

Cephalopods• Octopuses, squids,

cuttlefishes, and others• Active, complex

nervous system• Agile swimmers• Foot modified into arms

& tentacles– “cephalopod” translates

to head-footed

• Large eyes, similar to ours

Cephalopods

• Lack a hard shell (except for the chambered nautilus)– Squid and cuttlefish have

hard shells inside the body

• All are carnivores• All have a mantles• Eyes have cornea, lens,

and retina

Octopuses: How They Move

• Jet propulsion!• Move by taking in

water to the mantle then forcing it out the siphon– Siphon points all

directions

• Can move up to 25 mph

Octopuses: All sizes

Can change shape

Can Change Color

Ink used to distract predators

Great Hunters: a built in Swiss army knife

• Retractable beak (similar to a parrot’s)– Breaking open clam

shells and tearing flesh

• Radula– Used to scrape animals

out of shells

• Salivary Papillas– Drills into shells– Secretion erodes shell

and weakens prey

Octopus vs. Shark

Chambered Nautilus• Lives 400 m deep, but

ascends up to look for food at night

• Contains gas filled floatation chambers in shell

• Closest relatives are squid and octopus

• Tentacles have chemical sensors—detecting predators and prey

• Eats once a month

Cuttlefish

• There actually not fish at all. Let’s watch a movie…

Squid• Known for speed and

agility• Use jet propulsion

– Up to 23 mph, 12 feet out of the water

• Live 1.5-3 years• Swim in schools (unlike

other molluscs)• 10 arms, two are

tentacles

The Vampire Squid• Vampyroteuthis

infernalis• Found in tropical and

temperate regions• Ear-like fins• Only about 6 inches

long• Live at a depth of 3000

ft.• Has tooth-like spikes on

its arms

The Humboldt Squid

• Also known as jumbo squid or red devils

• Up to 6 ft and 100 pounds

• Live between 600 and 2200 feet deep

• 1-2 year lifespan• Cannibals• Very aggresive

Beak and Suckers

• Suckers have hooks and teeth

• Razor sharp beak

Dive with Humboldt Squid

GIANT Squid

• Largest: 59 ft long, 900 kg (just under a ton)

• Biggest invertebrate on earth

• Largest eyes in animal kingdom (10 cm across)

• Deep sea is their home

That’s a big, dead squid!

• Washed ashore, NZ, 1996

Mysterious…• First time photographed

alive was in 2006• 2,950 feet down in the

North Pacific Ocean in Japanese waters

Giant Squid footage

Giant Squid vs. Sperm Whale

• Remains of Giant Squid often found in Sperm whale’s stomachs

• Marks made by squid suckers have been seen on whale skin

• Let’s watch a movie