Phylum Molluscs

http://www.youtube.com/watch?v=Gg57Idz7Bs4http://www.youtube.com/watch?v=vP_td9q_344

GeneralName means soft bodythis is one of the largest animal phyla, besides ArthropodaThere are nearly 75,000 species and some 35,000 fossil speciesVery diverse group (snails, clams, octopus)Range from simple organisms to some of the most complex invertebrates

Hawaiian Bobtail Squid

Blue Ringed Octopus

Ecological RelationshipHabitats: from tropics to polar regionponds, lakes, streams, surf, ocean depths, etcMost live in the seaInclude herbivores, carnivores, and filter feedersEconomic Importancemany are food for humansproduce pearls (most from Eastern Asia)Some molluscs are destructive (Great Lakes, Snails and Slugs in gardens)

Form and FunctionBody Plan consist of head-foot portion (cephalopod) and a visceral mass (nervous system)head-foot portion contains feeding, cephalic sensory, and locomotion organsvisceral mass contains digestive, circulatory, respiratory, and reproductive organs

Form and FunctionBody Plan two folds of skin make up a protective mantlemantle houses the lungs and secretes a shell in many speciesForm and FunctionHead-foot many have a well developed head containing sensory organsrange from simple to complex eyesFoot is used for locomotion

Form and FunctionHead-foot Unique structure inside mouth called radulaIt is a tonguelike found in all molluscs except bivalves (shell fish)Has rows of tiny teeth that point backwardIt has about 250,000 teeth When protruded, it can scrape, pierce, tear, or cut food materialhttp://www.youtube.com/watch?v=mLVDwlrSq5U&list=TLDlxJTSuqf42kySqHbo0jexNdvt3BkIqS

Form and FunctionHead-foot Foot can be adapted for locomotion, attachment, or a combination of functionsSome modifications include hatchet foot of bivalves, funnel for jet propulsion in squids and octopi

Form and FunctionVisceral Mass (mantle and mantle cavity)mantle the outside of the skin extending from the visceral hump that runs down each side of the body, protecting soft parts and creating a spaceForm and FunctionVisceral Mass (mantle and mantle cavity)mantle cavity houses respiratory organsproducts from digestive, excretory, and reproduction systems empty into the mantle cavityin aquatic species, surface cilia create water currents that continually flush out waste

Form and FunctionVisceral Mass Shell (when present) typically has three layersouter layerComposed of a protein called conchiolinGrowth only occurs at the edge of the shellmiddle layer Composed of densely packed prisms of calcium carbonate in a protein matrixInner layerComposed of calcium carbonate sheets laid down over a thin protein matrixThis layer is continuously secreted by mantle surface, so it becomes thicker during the animals lifeCalcium for the shell comes from environmental water, soil, or food

a. Outer layer b1. middle layerb2. Inner layer

Form and FunctionInternal Structure and Function there is an open circulatory systempumping heartblood vessels blood sinusesclosed circulatory system

Form and FunctionInternal Structure and Function Digestive tract is highly specialized according to feeding habitsMost have a pair of kidneysDucts of kidneys in many forms serve to discharge eggs and sperm

Form and FunctionInternal Structure and Function Nervous System consists of several pairs of ganglia (nerve cells) with connected nerve cordsMost molluscs are dioecious Some are hermaphroditicMating Leopard Slugshttps://www.youtube.com/watch?v=FhVi4Z6CjZk Class Polyplacophora: Chitonsare somewhat flattened and have a surface that bears eight plates, or valvesname means bearing many platesmost are between 2 and 5 cmcommonly occur on rocky surfaces in intertidal regionsif detached, they can roll up like an Armadillo for protectionSexes are separate

Class Gastropoda(gastro stomach, podos foot)By far the largest and most diverse classContains about 40,000 living speciesIncludes snails, limpets, slugs, whelks, conchs, periwinkles, sea slugs, sea hares, sea butterflies, etc.Often sluggish, sedentary animalsBecause of heavy shells and slow locomotion organs

Snails

Snails

Limpets (Owl Limpet)

Limpets

Slugs

Whelks

Whelks (Lightening)Conchs

ConchsConchs

Periwinkles

Periwinkles

Sea slugs

Sea slugs

Sea slugsFrosted Sea Slug

Sea hares

Sea hare

Sea hare

Sea butterfliesClass GastropodaBasically bilaterally symmetrical, but because of torsion, the visceral mass is asymmetricalTorsion a twisting process that occurs during development

Class GastropodaThree subclasses Prosobranchia (largest)Almost all marinePeriwinkles, limpets, whelks, conchs, abalones, slipper shells, oyster borers, rock shells, cowriesOpisthobranchiaSea slugs, sea hares, nudibranchs, canoe shellsPulmonataMostly land and freshwater snails and slugsUsually have two pairs of tentacles

Nudibranchs

NudibranchsClass Bivalvia(two-shelled)Includes mussels, clams, scallops, oysters, shipwormsMost are sedentaryUnlike gastropods they have no head, radula, and little cephalization

Class BivalviaMost are marine, but many live in brackish water and in stream, ponds, and lakesTheir two shells (valves) are held together by a hinge ligamentAdductor muscles work in opposition to the hinge ligament and draw the valves togetherZebra mussels

Zebra mussels (Lake Mead)Preventing Mussels in Idahohttps://www.youtube.com/watch?v=J4EVAy8adMk http://www.youtube.com/watch?v=T18E58vOTus

Class Cephalopodamost complex speciesinclude squids, octopuses, nautiluses, cuttlefishesAll are marineAll are active predatorsHave an odd body plan Develops as the embryonic head and foot become indistinguishableThe ring around the mouth bears arms and tentaclesClass CephalopodaRange from 2 to 3 cm to 13 meters

Giant Squid

Slash marks from Giant SquidThe Search for the Giant Squidhttps://www.youtube.com/watch?v=EbubjXsA4S4 Class CephalopodaMost have special pigment cells called chromatophores in their skinBy expanding and contracting, they produce color changeSome color change are for protection to match the backgroundMost change is behavioral, associated with alarm or courtshipMany deep-sea squid are bioluminescentWhen the animal is alarmed, it releases a cloud of ink through the anus to form a smokescreen to confuse an enemy

SquidMimic Octopus and othershttps://www.youtube.com/watch?v=t-LTWFnGmeg&feature=related

Octopuses

OctopusesOctopuses

Blue Ringed OctopusThe most venous octopus. This small mollusc lives in warm, shallow reefs off the coast of Australia, new Guinea, Indonesia and the Philippines. It has a life span of about one and a half years.

Blue Ringed Octopus It is said that the venom of this octopus could kill 26 adults in just a few minutes. There is no antivenin for treatment. Fortunately, these octopuses do not attack humans. Injury typically occurs when a blue-ringed octopus is stepped on or picked up.83

Nautiluses

Nautiluses

Nautiluses Cuttlefishes

Cuttlefishes

Cuttlefishes