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Mollusca Bio 1413: General Zoology Lab (Ziser, 2008) Exercise 11 (p 171) Identifying Characteristics of Phylum: -triploblastic with true coelom -bilateral symmetry; some with secondary assymetry -soft, usually unsegmented body consisting of anterior head, ventral foot and dorsal visceral mass -body usually enclosed by thin fleshy mantle -mantle usually secretes hard external shell -complete digestive tract, many with a radula; a rasping or scraping feeding organ -respiratory system consists of gills in aquatic forms or "lung"-like chamber in terrestrial forms -most with open circulatory system; body cavity (coelom) a haemocoel -marine forms with characteristic trochophore larva Cell Types and Characteristic Structures: -shell consists of three layers, from outside - in, periostracum, prismatic layer and nacreous layer -characteristic trochophore larva - distinctive radula used as main feeding tool in most groups Body Organization: -body usually consists of anterior head with radula, ventral muscular foot and dorsal visceral mass containing most internal organs,and gills -almost all molluscs have the basic molluscan features; shell, mantle, foot, gills, radula and head but they have been variously modified in each class Classification: Class: Class: Class: Class: Class: Class: Class: Class: Monoplacophora Caudofoveata Solenogastres Polyplacophora (Chitons) Scaphapoda (Tusk Shells or Tooth Shells) Bivalvia (Clams) Gastropoda (Snails) Cephalopoda (Octopi and Squid) Lab Activities: 1. Read description and discussion of molluscs in the lab manual beginning on page 169 2. The Freshwater Clam, Class Bivalvia (p 172) -external structure (p173): know: hinge, umbo, growth lines preserved: clam 3. The Mollusc Shell (p 175) preserved: clam shells -know and distinguish between: periostracum, prismatic layer, nacreous layer 4. Clam, internal structure (p173): know: anterior and posterior adductor, pallial line, teeth, mantle, incurrent & excurrent siphons, aperture (siphons), pericardium, visceral mass, foot, gills, labial palps 5. Bivalve Gills (p 175) -note structures in preserved clam as assigned -make wet mount of transverse section if time permits slide: mussel gills, cs 6. Bivalve Reproduction (p179) slides: mussel glochidia, -note structures in preserved clam as assigned wm -be able to recognize a marsupium or brood chamber, Patella trochophore if present in any preserved clams -make a wet mount of gonadal tissue and determine whether eggs or sperm are present -recognize the glochidia larva of freshwater clams -be able to recognize a trochophore larva from slide 7. Dissection of Oyster (if available; see handout) know: shell, adductor muscle, gills, mantle, mouth, anus, palpus, intestine, pericardium, heart 8. Class Gastropoda (Ex 11B): a. Pulmonate Land Snail, Helix (p180) -note structures and behaviors as described if live specimens are available -surface anatomy: know: shell, apex, growth lines, head, foot, tentacles, eyes, mouth b. Slug, Limax -use fig 11-9 to find: eyes, tentacles, mantle, pneumostome 9. Radula (p181) -recognize radula as characteristic molluscan feeding structure fresh(if available):oyster preserved: Helix preserved: Limax slide: snail radula wm 10. A Squid: Loligo; Class Cephalopoda Ex 11D; (p184) preserved: squid a. External anatomy (p 184) fresh(if available): squid -know: head, arms, fins, mantle, eyes, suckers, tentacles, mouth, funnel, beak -be able to distinguish between the male and female and know associated structures b. Internal Anatomy (p 186) -know: mantle cavity, gills, hearts, ovaries, testes, ink sac, stomach, cecum with spiral valve, pen -which structures are easier to see in the fresh squid (if available)? In the preserved squid? 11. Chiton Ex 11C (p 183) -know: mantle, girdle, head, mouth, gills, foot shell plates preserved: Katharina Demonstrations: • Mollusc anatomy: use the additional figures to help identify the anatomical features you are responsible for. • Diversity of Molluscs: be able to recognize the classes of each of the figures, preserved and fresh specimens and shells available Notebook Suggestions: Observe and describe the movement, feeding and behaviors of living representatives as available Make a table indicating how the basic molluscan anatomical features vary among the different classes