Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Phylum Molluscs
Transcript
http://www.youtube.com/watch?v=Gg57Id z7Bs4 http://www.youtube.com/watch?v=vP_td9 q_344 General Name means soft body this is one of the largest animal phyla, besides Arthropoda There are nearly 75,000 species and some 35,000 fossil species Very diverse group (snails, clams, octopus) Range from simple organisms to some of the most complex invertebrates Hawaiian Bobtail Squid Blue Ringed Octopus Ecological Relationship Habitats: from tropics to polar region ponds, lakes, streams, surf, ocean depths, etc Most live in the sea Include herbivores, carnivores, and filter feeders Economic Importance many are food for humans produce pearls (most from Eastern Asia) Some molluscs are destructive (Great Lakes, Snails and Slugs in gardens) Form and Function Body Plan – consist of head-foot portion (cephalopod) and a visceral mass (nervous system) ◦ head-foot portion – contains feeding, cephalic sensory, and locomotion organs ◦ visceral mass – contains digestive, circulatory, respiratory, and reproductive organs Form and Function Body Plan – two folds of skin make up a protective “mantle” ◦ mantle houses the lungs and secretes a shell in many species Form and Function Head-foot – many have a well developed head containing sensory organs ◦ range from simple to complex eyes Foot is used for locomotion Form and Function Head-foot – Unique structure inside mouth called “radula” ◦ It is a tonguelike found in all molluscs except bivalves (shell fish) ◦ Has rows of tiny teeth that point backward ◦ It has about 250,000 teeth ◦ When protruded, it can scrape, pierce, tear, or cut food material ◦ http://www.youtube.com/watch?v=mLVDwl rSq5U&list=TLDlxJTSuqf42kySqHbo0jexNd vt3BkIqS Form and Function Head-foot – Foot can be adapted for locomotion, attachment, or a combination of functions Some modifications include – “hatchet foot” of bivalves, funnel for jet propulsion in squids and octopi Form and Function Visceral 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 space Form and Function Visceral Mass – (mantle and mantle cavity) mantle cavity – houses respiratory organs products from digestive, excretory, and reproduction systems empty into the mantle cavity in aquatic species, surface cilia create water currents that continually flush out waste Form and Function Visceral Mass – Shell (when present) typically has three layers ◦ outer layer Composed of a protein called “conchiolin” Growth only occurs at the edge of the shell ◦ middle layer Composed of densely packed prisms of calcium carbonate in a protein matrix ◦ Inner layer Composed of calcium carbonate sheets laid down over a thin protein matrix This layer is continuously secreted by mantle surface, so it becomes thicker during the animals life Calcium for the shell comes from environmental water, soil, or food a. Outer layer b1. middle layer b2. Inner layer Form and Function Internal Structure and Function – there is an open circulatory system ◦ ◦ ◦ ◦ pumping heart blood vessels blood sinuses closed circulatory system Form and Function Internal Structure and Function – Digestive tract is highly specialized according to feeding habits ◦ Most have a pair of kidneys Ducts of kidneys in many forms serve to discharge eggs and sperm Form and Function Internal Structure and Function – Nervous System consists of several pairs of ganglia (nerve cells) with connected nerve cords Most molluscs are dioecious ◦ Some are hermaphroditic Mating Leopard Slugs https://www.youtube.com/watch?v=FhVi4Z6CjZk Class Polyplacophora: Chitons are somewhat flattened and have a surface that bears eight plates, or valves name means “bearing many plates” most are between 2 and 5 cm commonly occur on rocky surfaces in intertidal regions ◦ if detached, they can roll up like an Armadillo for protection Sexes are separate Class Gastropoda (gastro – stomach, podos – foot) By far the largest and most diverse class ◦ Contains about 40,000 living species Includes snails, limpets, slugs, whelks, conchs, periwinkles, sea slugs, sea hares, sea butterflies, etc. Often sluggish, sedentary animals ◦ Because of heavy shells and slow locomotion organs Snails Snails Limpets (Owl Limpet) Limpets Slugs Whelks Whelks (Lightening) Conchs Conchs Conchs Periwinkles Periwinkles Sea slugs Sea slugs Sea slugs Frosted Sea Slug Sea hares Sea hare Sea hare Sea butterflies Class Gastropoda Basically bilaterally symmetrical, but because of “torsion,” the visceral mass is asymmetrical ◦ Torsion – a twisting process that occurs during development Class Gastropoda Three subclasses – ◦ Prosobranchia (largest) Almost all marine Periwinkles, limpets, whelks, conchs, abalones, slipper shells, oyster borers, rock shells, cowries ◦ Opisthobranchia Sea slugs, sea hares, nudibranchs, canoe shells ◦ Pulmonata Mostly land and freshwater snails and slugs Usually have two pairs of tentacles Nudibranchs Nudibranchs Class Bivalvia (two-shelled) Includes mussels, clams, scallops, oysters, shipworms Most are sedentary Unlike gastropods they have no head, radula, and little cephalization Class Bivalvia Most are marine, but many live in brackish water and in stream, ponds, and lakes Their two shells (valves) are held together by a “hinge ligament” “Adductor muscles” work in opposition to the hinge ligament and draw the valves together Zebra mussels Zebra mussels (Lake Mead) Preventing Mussels in Idaho https://www.youtube.com/watch?v=J4EVAy8ad Mk http://www.youtube.com/watch?v=T18E58vOTu s Class Cephalopoda most complex species include squids, octopuses, nautiluses, cuttlefishes All are marine All are active predators Have an odd body plan ◦ Develops as the embryonic head and foot become indistinguishable ◦ The ring around the mouth bears arms and tentacles Class Cephalopoda Range from 2 to 3 cm to 13 meters Giant Squid Slash marks from Giant Squid The Search for the Giant Squid https://www.youtube.com/watch?v=EbubjXsA4S4 Class Cephalopoda Most have special pigment cells called “chromatophores” in their skin ◦ By expanding and contracting, they produce color change ◦ Some color change are for protection to match the background ◦ Most change is behavioral, associated with alarm or courtship ◦ Many deep-sea squid are bioluminescent When the animal is alarmed, it releases a cloud of ink through the anus to form a “smokescreen” to confuse an enemy Squid Mimic Octopus and others https://www.youtube.com/watch?v=tLTWFnGmeg&feature=related Octopuses Octopuses Octopuses Blue Ringed Octopus The 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. Nautiluses Nautiluses Nautiluses Cuttlefishes Cuttlefishes Cuttlefishes
