Mollusks

• Kingdom: Animalia• Phylum: Mollusca• Classes:– Cephalopoda-octopuses, squids, cuttlefish– Gastropoda- snails, nudibranchs– Bivalvia-clams, mussels, oysters– Polyplacophora- chitons

Mollusk Song

• http://www.youtube.com/watch?v=0a7j5prL8hc

• Mollusk puppet show http://www.youtube.com/watch?v=dEwnarCYIO4

• Mollusk beauty slide show http://www.youtube.com/watch?v=KCljGN0kkBg

Invertebrates• Molluscs• Characteristics of Phylum:

– More than 200,000 species– Name means "soft body"– Basic body plan – head, muscular foot and visceral mass in most

species– Mantle- secretes shell, waste disposal, sensory reception, respiration– Many have a shell of calcium carbonate– Radula for grazing is unique to this group– Some are deposit feeders, others carnivores, some use radula for

scraping algae, encrusting animals, etc. off substrates – Well developed nervous system– Open circulatory system– Complete digestive system– Trochophore larvae develops into a planktonic veliger larvae complete

with shell (miniature version of adult)

Body plan

• Study figure 7.20 page 127– Head/foot: head is mouth and sensory structures– Visceral mass: above head-food. Contains heart

and organs for digestion, excretion and reproduction. Covering this is a layer of epidermis called the mantle

Respiration and gas exchange

• Mantle– Secretes shells– Protects organism but also reduces surface area

for gas exchange– Organisms have gills• Provide large surface area with rich blood supply• Allows for diffusion to happen easily• Gills located in mantle cavity (hollow space under the

shell)

Mollusk Gills

Circulatory system

• Open system• Hemolymph- circulatory fluid– Does not remain within blood vessels– Once filled with oxygen, it travels to heart and

then is pumped throughout spaces and tissues

Nervous system

• Ganglia– Clusters of nerve cells located in head-foot and

connected by two long nerve cords to visceral mass

Digestive system

• Radula-– Flexible, tongue like strip of tissue covered with

tough, abrasive teeth that point backward– Radula can cut, scrape, drill, and harpoon

Mollusk Reproduction

Invertebrates• Types of Molluscs:– Chitons pg 132

• 800 species• All marine• Not coiled like snails• Dorsal shell of 8 plates.• Ventral muscular foot.• Ventral mouth with radula• Mostly found in shallow water, coastal environments of hard

substrate• Many graze on algae & small animals in marine intertidal zone

(area between high and low tides)• Chitons have separate sexes, fertilization is external• Animals which prey on chitons include humans, seagulls, seastars,

crabs, lobster, fish

• After a chiton dies, the individual valves which make up the eight-part shell come apart because the girdle is no longer holding them together, and then the plates sometimes wash up in beach drift. The individual shell plates from a chiton are sometimes known as "butterfly shells" because of their shape.

• The largest chiton (up to 33 cm in length) is the brick-red gumboot chiton.

Chitons

Chiton video

• http://www.youtube.com/watch?v=KD4M6uLCVLc

Invertebrates• Types of Molluscs:• Bivalves (body plan and representatives shown in Fig. 7.23 and Fig. 7.24,

pg. 130-131)– Clams, Oysters, Scallops, Mussels, etc.– Two shells or “valves”– Oldest part of the shell is called the umbo– Shell grows out from the umbo in concentric rings – No head present but still considered bilateral– No radula present. Filter feeders– Adductor muscles secure valves together. Closes shell.– Muscular foot used for burrowing in bottom and other locomotion.

Otherwise sessile– Water circulated with siphons– Gills for respiration & food gathering (filter feeding). Ctenidia– Some species burrow, others attach to hard substrates via byssal

threads, or grow attached to each other

• Most bivalves have a pair of large gills which are located in their mantle cavity. The gills enable them to extract oxygen from the water (to breathe) and to capture food. Water is drawn into the mantle cavity and washes through the gills. In species that burrow, a long siphon is extended to the surface to take in water. Mucus on the gills helps capture food and cilia transfer the food particles to the mouth. Once in the mouth, food passes into the stomach to be digested.

• Bivalves have a mouth, heart, intestine, gills, stomach and siphon but have no head, radula or jaws. They have an abductor muscle that, when contracted, holds the two halves of the shell closed. Bivalves have a muscular foot, which in many species such as clams, is used to anchor their body to the substrate or dig down into the sand

• The smallest living bivalve is one of the Nut Clams, Condylonucula maya. An adult Condylonucula, measures only 500 microns — less than 2 one-hundredths of an inch — about half a millimeter. The largest living bivalve is the Giant Clam, Tridacna gigas. This gentle giant can grow almost 5 feet in length (up to 1½ meters).

Nut clam

Giant clam

Monster of the Deep: Giant Clams

• National Geographic• http://www.youtube.com/watch?v=ZBfviWg7k

KM

clams

• Bivalves that live in mud or sand• Mantle cavity is sealed except for pair of

hollow, fleshy tubes called siphons• Incurrent siphon- water enters• Excurrent siphon- water leaves• Clams have separate sexes

Clam eating salt off table

• http://www.youtube.com/watch?v=Qp1nrhJAX3I

Dirty Jobs: Clam Shucker 6:08

• http://www.youtube.com/watch?v=iwrFHgiwJFg

Clam dissection

• http://www.youtube.com/watch?v=C-3GqvLswc8

oysters

Oyster journal

• Research pearl formation

• Although it is possible for food oysters to produce pearls, they should not be confused with actual pearl oysters, which are from a different family of bivalves

Oysters and water quality

• Oysters act as a natural filtration system; they filter silt and contaminants from the water. A single oyster can filter up to 50 gallons of water per day! A large, healthy oyster population filters large volumes of water and thereby improves local water quality and clarity.

• Because oysters filter their food from the water in which they live, if that water becomes contaminated they can concentrate harmful toxins in their meat.

• PSP is a biotoxin produced by the naturally-occurring dinoflagellate Alexandrium catenella. When consumed via contaminated shellfish, the biotoxin can produce symptoms within an hour or two, ranging from tingling or numbness of the lips to speech impairment and interference with breathing and moving. There is no known antidote and death may occur in some extreme cases.

Oyster reproduction

• They reproduce when the water warms by broadcast spawning, and will change gender once or more during their lifetime

• They change their gender at least once in their lifetimes. All oysters start off as male, but most change permanently to female by the time they are a year old. Their reproductive organs produce both sperm and eggs, and they can change gender at will. It is technically possible, therefore, for an oyster to fertilize its own eggs

Gastropods

• Can you name a gastropod?• What does “gastropod” mean?• Do all gastropods have shells?• Are all gastropods marine?

• Let’s find out!!!!!

Invertebrates• Types of Molluscs:• Gastropods

– Largest class of molluscs, about 75,000 species– Snails, limpets, abalone, conchs, slugs (figure 7.22)– Name means "belly-footed"– Coiled shell on most species. Twists in a clockwise direction– No shell on sea slugs (nudibranchs)– Radula for grazing on plants in most, some are deposit feeders – Some species are carnivorous and use radula for prey capture

(some will even prey on members of the same species)– Only marine group which have colonized terresterial habitats

• Visceral organs show well organized features, which include a nervous system, a heart and circulatory system, a digestive system, excretory system, and a reproductive system

• Both sexual and hermaphroditic reproduction are found among the various species and families

operculum

• Hardened structure on the surface of their foot

• Is it like a shoe??????• No!• Serves as a lid that protects the gastropod

when it retracts its body within the shell• Operculum seals the shell opening to prevent

injury from predators

torsion

• What is torsion?????• A type of torture?• Like a torsion tensor in differential geometery?• NO………………..• It’s so much more exciting than that!!!!

torsion

• During development torsion occurs. • Twisting of body (not shell) along its head to tail axis• Twisting means that the head is between 90 and 180

degrees offset relative to their foot• Start out bilateral then by adulthood they are

asymmetrical• The adult ends up configured in such a way that its

body and internal organs are twisted and the mantle and mantle cavity are above its head

torsion

6 groups

• Patellogastropoda• Vetigastropoda• Cocculiniformia• Neritimorpha• Caenogastropoda• Heterobranchia- most diverse

NO………..•You don’t have to memorize those names

• You’re welcome…..

• Ever seen a whelk?????

whelks

whelk

• whelk, any marine snail having a similar shell. Some are incorrectly called conchs. The sturdy shell is elongated and has a wide aperture in the first whorl. They feed on other mollusks through its long proboscis; some also kill fishes and crustaceans caught in commercial traps. Whelks occur worldwide

ScienceDaily: Male Welks

• http://www.sciencedaily.com/releases/2012/08/120828163036.htm

periwinkles

A Periwinkle is a small sea animal with a thick spiral shell

The common periwinkle is a popular food in Europe

Snails can Fly!

• http://blogs.cordovasd.org/marinebio/2011/11/13/snails-can-fly/

limpets

Limpets cling tightly to a rock (using the muscular foot). During the day, limpets move around by rippling the muscles of the foot in a wave-like fashion, looking for food. They return to the same place on their rock each night. No one knows exactly how they find their way back to the same spot each time.

limpets

Question……..

•Does Conch have bone????•Ask the experts

Conch

Listening to conch• Why can you hear the ocean in a seashell?

You can hear the sound of the "ocean" not just with seashells, but also with a coffee cup or glass, or even by cupping your hand loosely over your ear. The usual explanation is that the seashell amplifies the sound of blood moving in your ear. Two pieces of evidence suggest that this is not correct. First, the sound is the same before and right after exercise (try running up and down stairs or doing jumping jacks), but it should be louder after you exercise since blood would be moving faster. Second, the sound is not drowned out by loud noise such as that heard next to a window mounted air conditioner. A better explanation is that the shell (or glass) acts as a resonating chamber, bouncing surrounding sounds back and forth, jumbling and amplifying them. This means that you should be able to hear the "ocean" better in a noisy room than in a very quiet one.

Playing a conch

• http://www.youtube.com/watch?v=k-Uk0sXw_wg

Conch

• The term 'conch' (pronounced "konk") is used to describe over 60 species of sea snails which have a medium- to large-sized shell. In many species, the shell is elaborate and colorful. Probably the most well-known species is the queen conch, which is the image that might come to mind of a sea shell. This shell is often sold as a souvenir, and it's said you can hear the sea if you put a conch shell to your ear.

Live conch video

• http://www.youtube.com/watch?v=xQy87YKnSx8

“The Conch Republic”

• http://www.conchrepublic.com/

“What is conch” from a chef

• http://www.youtube.com/watch?v=LU2X-pOQMgU

nudibranch

nudibranch

• http://www.youtube.com/watch?v=n9Z8pd1yIyQ

Gastropoda videos

• Snails http://www.youtube.com/watch?v=DTMaqy39go0

• Nudibranchs http://www.youtube.com/watch?v=n9Z8pd1yIyQ

• Gastropods

•Cephalopods

• Name a cephalopod!• Name a distinguishing feature of a cephalopod

examples

• Let’s amuse ourselves with a little pre test

Invertebrates• Types of Molluscs:• Cephalopods– Name means “head foot” – Squid, Octopus, Nautilus, & Cuttlefish– 650 species – all marine– Foot modified into 8-10 arms or tentacles and a siphon– Fast swimming predators due to water jet propulsion– Well developed eyes– Thick mantle covers the body. No shell. Remnant inside

squid is called the “pen”– Use beak-like jaws and radula to crush or rip prey.

Sometimes with poison glands. Radula is behind the beak– Adapted tentacles– Ink sac- expels ink out of siphon to distract predators and

allow for escape

Invertebrates

– Shell internal or absent in most – Most advanced invertebrates– In octopus, the shell has been replaced by a beak-like jaw

which can deliver a powerful bite– Some octopus have toxic bites– Ink sac is also seen in octopus to allow escape from

predators– A stiff internal “pen” is seen in squid is a modified shell

What is the plural of octopus?

•Octopuses. Octopi is wrong, although generally accepted these days.

Members of the order Nautiloidea have more than 90 tentacles; members of orders Sepioidea and Teuthoidea have eight arms and two tentacles; and members of orders Ocotopoidea and Vampyromorpha have eight arms

hearts

• How many hearts does the octopus have?3

• Why do they have 3 hearts?Basically, when you have 8 legs you need extra blood flow, thus having more than one heart is necessary. Octopuses have three hearts. Two pump blood through each of the two gills, while the third pumps blood through the body.

brain

• Only mammals and birds have more complex brains than that of the octopus. Octopuses have excellent memories, have played with objects, unscrewed jars to get to the crab inside. Their brain has folds, another indication of complexity. They can be left-eyed or right-eyed like in humans with their hand preferences.

beak

beak

• The beak is the only hard part of an octopus and squid’s body. It is located on the lower side of the body. In the mouth is a radula, a toothed tongue for rasping. The beak is made of the same material, keratin, that a bird’s beak and our fingernails are made of. Octopuses use it to crush the crabs and mollusks that they feed on.

pen

• The ink is concentrated melanin, the same pigment that our makes hair and skin dark. Most octopuses have the ability to squirt this inky pigment, but not all. The ink also contains a compound called tyrosinase that irritates the eyes and sense of smell of the predator.

eyes

• Octopus and human eyes are similar even though they developed on different paths. Each has a cornea, an iris, an accommodating lens, a fluid-filled vitreous humor, a retina, and so forth.

• Octopus eyes focus like a camera with the lens moving in or out while our eyes use muscles to squeeze the lens to focus. The octopus eye, like other invertebrate eyes, develops as an invagination, or in-pocketing, of the skin. Human eyes develop as extensions of the brain.

Octopus life expectancy

• 6 months for smaller ones and up to 5 years for larger ones like the Giant Pacific octopus. Breeding is what does them in as they stop eating after breeding and essentially starve to death.

What is the smallest octopus?The Octopus Wolfi is half an inch long and weighs 1 gram

Largest octopus

• Enteroctopus dofleini, also known as the Giant Pacific Octopus or North Pacific Giant

camoflauge

• Chromatophores can you find the coral octopus?

reproduction

• Cephalopods are gonochoric. A female typically possesses a single oviduct. A male produces spermatophores that it transfers to the female's genital pore by means of a specialized arm or tentacle. In some species, the specialized arm tip may be pinched off and left in the female's mantle cavity: this is known as the hectocotylus arm. Mating in some cephalopods includes courtship rituals that may consist of color changes, body movements, or combinations of both. Cephalopods exhibit spiral cleavage and are protostomous, but they have no larval stage: their development is direct. Octopods typically tend their eggs until hatching. Most cephalopods are semelparous

Octopus video

Cephalopod dissection

Mollusk review video

• http://www.youtube.com/watch?v=RvyMBRquwEA