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Slide 2 PHYLUM MOLLUSCA Slide 3 Mollusks Mollusks (Mollusca) extremely diverse characterized by a coelom great economic significance pearls mother of pearl economic / environmental costs zebra mussel invasion intermediate hosts for parasites Slide 4 Body Plan of the Mollusks Distinct bilateral symmetry Digestive, excretory, and reproductive organs are all concentrated in a visceral mass and a muscular foot. May have differentiated head Folds constituting a mantle gills - increased surface area for gas exchange Shells serve primarily for protection Radula - rasping tongue-like organ used for feeding Circulatory system (except cephalopods) consists of a heart and an open circulatory system. Nitrogenous wasted removed by nephridia Slide 5 Mollusk Body Plans Slide 6 Slide 7 Reproduction in mollusks most have distinct male and female individuals most engage in external fertilization many have free-swimming larvae (trochophores) which closely resemble larval stage of many marine annelids Slide 8 Mollusks & Movement Foot Muscular organ to move, dig, slide Radula Rasping tongue to obtain food or drill holes in other shells Photo credit: USGS Slide 9 Function of the Radula A layer of flexible skin, with hundred of sandpapery teeth, used to scrape algae off of rocks In full-on carnivore mode, the radula acts like a drill to pierce shells. These things even have poison glands to make things nastier Octopi and certain sea slugs do this. Slide 10 Class Gastropoda snails, slugs, sea slugs Slide 11 Incredible diversity of shell form Slide 12 Gastropods The largest class. Snails, slugs, and sea slugs Sometimes called the univalves (one shell) Live in water or on land Herbivores that use a radula to scrape food from surface. Visceral mass- Body found within the shell. Moves by a muscular foot Slide 13 Open circulatory - blood flows through vessels, open spaces within body. Aquatic gastropods-gills for respiration; land gastropods -mantle for gas exchange. Nephridia - Filter wastes from the blood. Most land univalves are hermaphroditicaquatic univalves - separate sexes with external fertilization. The abalone and conch are examples of marine univalves. Gastropods Slide 14 Naked gastropodsthe slugs Thick layer of mucus coating bodies-no shell Nudibranchs Sea slugs that feed on jellyfish and incorporate the nematocysts into their own tissues. Some sea slugs secrete a poisonous mucus for protection. Slide 15 Class Bivalvia clams, cockles, mussels, oysters, scallops Slide 16 Freshwater mussels in Iowa! Slide 17 Life cycle of the unionid bivalve + Slide 18 Bivalvia: bivalves clams, scallops, mussels and oysters two lateral shells hinged together dorsally mantle secretes shell and ligaments most are sessile filter-feeders Slide 19 BIVALVES Clams, Scallops, and Oysters Most are marine invertebrates. Open circulatory system Large muscular foot for digging. No distinct head Filter feeders. Gills are coated with mucus which trap food particles and oxygen. Mantle -Secretes the shell. Any particle caught in between the shell and mantle is coated to stop irritation (pearl) Slide 20 pearls Mother-of-pearl inner smooth part of bivlave shell. Made primarily by oysters when a foreign object gets lodged inside between mantle and shell. Come in many colors Slide 21 Class Cephalopoda squids, octopus, cuttlefish, nautilus Slide 22 Cephalopoda: octopuses, squids, nautilus most intelligent of the invertebrates active marine predators foot evolved into a series of tentacles equipped with structures to capture prey highly developed nervous systems Slide 23 Cephalopods Head-footed mollusks Octopus, Squid, and Chambered nautilus Most intelligent (Well developed nervous system) Only mollusk group which are all predators Free swimming Tentacles with suckers surrounding the head are used for moving and capturing prey. A sharp beak-like radula for ripping apart prey. Closed circulatory system (blood moves through blood vessels and is most efficient) Slide 24 Adaptations to predatory life style Active and very mobile Close circulatory systems Camouflage Chromatophores in skin http://www.youtube.com/watch?v=S CgtYWUybIEhttp://www.youtube.com/watch?v=S CgtYWUybIE Exceptional vision Beak to tear prey Arms (tentacles) to grip prey Slide 25 Bioluminescence! Complicated Chemical Reactions!