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Lab 4 Exam 1 Next Week! MOLLUSCA & ANNELIDA •! 60 questions (1 point each) •! 30 stations •! 3 extra credit questions •! ~ 1 hour to complete Open lab for review: Friday 10:30-12:30 Phylum Mollusca Chapter 11 General Characteristics –! Bilateral symmetry –! Complete digestive system –! Open circulatory system –! True (complete) coelom –! Primitive excretory/ osmoregulatory system Phylum Mollusca –!Most have •!Mantle (secretes the shell) •!Radula (chitinous ribbon with rows of teeth) •!Gills (except terrestrial snails/slugs) •!Muscular foot (some have evolved into a muscular head) –!Class Cephalopoda – “head-foot” The four classes of mollusks we’ll study are… •! The body of a mollusk has three main parts: a muscular foot, a visceral mass, and a mantle mass •! The body ofVisceral a mollusk has three main parts: a muscular foot, a visceral Reproductive Coelom organs Mantle mass,Kidney and aHeart mantle Digestive Class Polyplacophora, (chitons) Protected by 8 overlapping calcareous plates tract Mantle cavity Shell Radula Radula Anus Gill Foot Mouth Nerve cords Mouth Class Bivalvia, (clams, oysters, mussels, & scallops) Protected by shells divided into two halves Class Gastropoda, (snails and slugs) Protected by a single, spiraled shell or have a hydrostatic skeleton Class Cephalopoda, (squids, octopuses, and nautilus) Exoskeleton, Endoskeleton, or Hydrostatic Skeleton Dissecting the Clam •! Cut through the adductor muscles to open the clam –! Tip: don’t twist the scalpel Clam external anatomy Dissecting the Clam –! Slowly open the valves, You may have difficulty seeing the siphons if you rip the mantle. •! Once you have the clam open explore the internal anatomy Incurrent siphon Excurrent siphon Structures •! Basic parts: –! Shell •! Also called valve –! Muscles •! Adductor –! Mantle •! Lines the shell –! Gills •! What do they do? –! Visceral mass / foot •! Most of the remaining functions! Dissecting the Clam “butterfly cut” Continue Dissecting the Clam •! Using your scalpel slowly cut into the visceral mass –! Do this in a few individual slices –! You’re “butterflying” open the visceral mass •! Take a look around inside once you cut it open •! Identify internal structures Freshwater Clam/ Mussel life cycle Glochidium larva (parasitize fish) Phylum Annelida (segmented worms) Characteristics Chapter 12 –! Bilateral symmetry –! True coelom –! Longitudinal and Circular muscles –! Paired nephridia in multiple segments (osmoregulation/excretion) –! Segmented –! Well developed closed circulatory system •! True coelom ( True body cavity ) Body covering The two classes of annelids we’ll study are… Class Polychaeta, (marine worms) have parapodia Tissue layer lining coelom and suspending internal organs Digestive tract Mesentery True coelom (e.g., annelid) Figure 17.8 Parapodia - Observe preserved specimens Class Clitellata, lack parapodia Subclass Hirudinea (Leeches) the two subclasses within Clitellata we’ll study are… all have 34 segments, suckers, and some are parasitic Subclass Oligochaeta (Earthworms), which eat their way through soil Saliva contains a local anesthetic and the anticoagulant hirudin Giant Australian Earthworm The earthworms The live earthworm dissection •! BEFORE you start –! Have everything ready –! Dissection tray, pins, dissection kit, moist paper towel etc. •! Anaesthetize earthworms for ~30 seconds in ethanol •! To work on them –! Pin them down at the front and back Secretes material that forms the cocoon in which fertilized eggs are incubated •! Dorsal (dark side) up •! Put them on moist paper towel –! Take scissors and cut from clitellum to anterior end –! Spread and pin tissue apart Live earthworm dissection Live earthworm dissection Use scissors – slowly lift and snip…lift and snip Use dissecting scope to see blood move in and out of hearts Anterior region from a freshly dissected live earthworm One last thing to look at intestine dorsal blood vessel •! Look for the typhlosole crop seminal vesicles gizzard Hearts (5 aortic arches) seminal receptacles –! Make a longitudinal incision in the intestine to see this •! Can see this well on the cross section slide Dissection Safety / Clean-up •! Wear gloves when touching preserved specimens. •! Use common sense with sharp tools. –! Report any injuries to me immediately. •! Rinse off (and dry) all tools, and the dissection tray, to keep them from rusting. •! Do not make unnecessary cuts. •! Do not throw animal parts in the trash or sinks! –! Bring finished specimens to me for disposal. Don’t forget to look at the side benches. There is more to see!