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PHYLUM MOLLUSCA

PHYLUM MOLLUSCA. General Information: Soft bodies usually protected by shell. True coelom. I. General Information. Usually have 3 body regions: a. Head/foot - locomotion & retraction of body into shell. b. Mantle - thin skin layer covering visceral mass; secretes shell.

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PHYLUM MOLLUSCA

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  1. PHYLUM MOLLUSCA

  2. General Information: • Soft bodies usually protected by shell. • True coelom

  3. I. General Information • Usually have 3 body regions: a. Head/foot- locomotion & retraction of body into shell. b. Mantle- thin skin layer covering visceral mass; secretes shell. c. Visceral mass- organs for digestion, excretion, circulation, reproduction

  4. II. Classification • Kingdom Animalia • Phylum Mollusca 3a. Class Gastropoda- snails, slugs 3b. Class Bivalvia- clams, oysters, mussels 3c. Class Cephalopoda- squid, octopus

  5. IIIa.Class Gastropoda • Snails, slugs • Marine, freshwater, • terrestrial • 3. Largest & most varied class • 4. Some have shell- univalves (one shell) • a. Apex- center spiral, oldest part of shell • b. Operculum- “door” that closes shell to prevent dehydration.

  6. Apex Eyespots Shell Pneumostome Tentacle Operculum Mouth Foot Head/anterior

  7. Locomotion • 1. Wave-like contractions of muscular foot. • 2. Lay down layer of mucus (terrestrial)

  8. Digestion/Feeding • 1. Have radula- tongue-like organ with tooth-like structures for scraping food. • 2. Mostly herbivores (algae); some predators • (cone snail- highly venomous) • 3. Mouth, pharynx, esophagus, stomach, intestine, anus. • 4. Salivary & digestive glands help breakdown food

  9. Respiratory System • 1. Gills- aquatic • 2. lungs/diffusion- terrestrial • 3. Pneumostome- opening to allow oxygen to enter body.

  10. D. Circulatory System 1. Open circulatory system- blood leaves short vessels and bathes tissues directly in blood. 2. Pulmonary vein- conducts oxygen from gills to heart via blood. 3. Heart- pumps blood rich in oxygen to rest of body thru aorta. 4. Aorta- dumps blood into spaces around organs

  11. Excretory System • 1. Nephridium- removes excess liquid waste, sends to mantle cavity where released to outside. • 2. Aquatic- release liquid ammonia waste • 3. Terrestrial- release uric acid in crystal form to prevent water loss.

  12. F. Nervous/Sensory System 1. Six ganglia throughout body. 2. Sensory structures located at anterior end- most sensitive area-retreats into shell first. a. Anterior tentacle- at front of head b. Posterior tentacle- behind anterior antennae; have eyes that detect light c. Osphradia- chemoreceptors that detect food and predators.

  13. G. Reproductive System • Most are monoecious. • Can be protandric- testes develop first & after they degenerate, ovaries mature. 3. Eggs are fertilized internally & layed as sticky mass. 4. Some marine gastropods are dioecious.

  14. Economic/Environmental Significance • 1. Source of food (escargot) & part of food chain • 2. Slugs destroy gardens/crops • 3. Hosts for parasites of man (flukes) • 4. Shells can be used as a source of jewelry • 5. Venom can be used in medicine

  15. IIIb. Class Bivalvia • Clams, oysters, mussels, scallops. • All marine or freshwater • Second largest class • All have 2 shells

  16. A. Locomotion • Clams/mussels- muscular foot for burrowing • Oysters- adults are sessile 3. Scallops- “clap” shell

  17. B. Shell Features Periostracum Prismatic 1. Shell structure a. Periostracum- thin outer layer of protein b. Prismatic layer- thick middle layer of calcium carbonate c. Nacreous layer- inner layer; secretes nacre which forms pearls in some. Nacreous

  18. 2. Umbo- swollen area near anterior, dorsal end of clam; oldest part of shell. 3. Hinge ligament- holds two shells together 4. Growth lines- wider lines indicate more growth/better feeding season. 5. Anterior and Posterior adductor muscles- very strong muscles for opening or closing shell.

  19. C. Digestion/Feeding 1. Filter feeders- algae, larvae, small particles 2. Food/water enter incurrent siphon. 3. Food swept into mouth by 2 pairs of palps 4. Esophagus, stomach, intestine, anus 5. feces/excess water leave thru excurrent siphon.

  20. D. Respiration • Oxygenated water enters incurrent siphon. • Gills have tubes where water & blood are close together. Gases exchange by diffusion across the membrane. 3. Deoxygenated water leaves thru excurrent siphon.

  21. E. Circulation 1. Open 2. Heart and short vessels similar to gastropods.

  22. F. Excretion 1. Nephridium • Nervous/Sensory System 1. Ganglia concentrated in foot, esophagus, adductor muscle and mantle. 2. Some have eyes for sensing light around shell rim. 3. Osphradia- chemoreceptors

  23. H. Reproduction 1. Most are dioecious- external fertilization 2. Sperm leave thru excurrent siphon 3. Sperm brought in thru incurrent siphon of female. 4. Clams release trochophore larvae which develop into adults.

  24. 5. Mussels release glochidia which look like miniature adults. • These are usually parasitic on fish. • Attach to fish gills & feed on blood. • When adult organs form, they drop off & take on filter feeding life style.

  25. Economic/Environmental Significance • 1. Source of food/part of food chain • 2. Filter/clean water of harmful pollutants (algae)- can cause sickness if red tide algae are eaten. • 3. Form pearls/jewelry • 4. Mother of pearl buttons made from shells

  26. YOU HAVE FINISHED YOUR BIVALVE NOTES-COME GET A COLORING OR DRAWING SHEET FROM ME

  27. Unit 4A JOURNAL #5 3/21 • Compare & contrast bivalves & gastropods.

  28. For the female have labeled- pen, cecum, ink gland, nidamental glands, gills, esophagus, ovary, anus • For the male have labeled- pen, gonad, cecum, heart, gills, ink sac, esophagus, anus

  29. IIIc. Class Cephalopoda • Squid, octopus, nautilus, cuttlefish • All marine • Most complex mollusk • No external shell, have internal support • a. Squid- have internal chitinous structure called pen

  30. b. Cuttlefish- have cuttlebone. Can be used as calcium supplement for birds. c. Chambered nautilus- has true shell

  31. d. Octopus- has no shell

  32. Anterior Dorsal Ventral Posterior

  33. Dorsal • Anterior View • Fin • Mantle • Body tube • Articular ridge • Eye • Arm • Tentacle • Buccal cavity fin mantle Body tube Articular ridge eye arm Buccal cavity tentacle Ventral

  34. Locomotion • 1. All cephalopods can • move by jet propulsion- • forcefully expelling water from siphons on head. • 2. Octopus crawl with arms. • 3. Squid & cuttlefish have posterior fins for steering/movement.

  35. Digestion/Feeding • 1. Have arms with suction cups to capture/hold prey. • 2. Sharp beak for tearing into prey. • 3. Radula for drilling holes in shells. • 4. Use extracellular digestion- secrete enzymes that breaks down food before enters mouth. • 5. mouth, esophagus, stomach (cecum = digestive gland), intestine, anus, siphon • 6. Most nocturnal- eat • crustaceans, fish, • other mollusks, etc. Radula Beak

  36. Holes created by octopus radula. “b” indicates where octopus gave up and used beak to break into shell.

  37. Respiratory System 1. Gills in mantle cavity • Circulatory System • Closed- blood enclosed in blood vessels. • Have hemocyanin- copper rich blood (blue) • Excretory system 1. Nephridia

  38. Nervous/Sensory System • 1. Large brains- good memory, can work thru problems. • 2. Complex eye- very similar to human eye. Can form images and distinguish color

  39. Camouflage • a. Chromatophores- pigments cells in skin which allow color change. Can also use to communicate with other cephalopods (mating, aggression, fear, etc) • b. Suckers on arms are very sensitive. Can change texture of skin to match rocks.

  40. Ink gland • ejects ink cloud when disturbed to make quick getaway. • tyrosinase- also released to irritate predators eyes and paralyze sense of smell

  41. G. Reproduction 1. Dioecious 2. Male testes package sperm in a case called a spermatophore. 3. He uses his enlarged tentacle- hectocotylus- to transfer spermatophore to female’s mantle cavity. • Female lays eggs which pick up sperm on the way out. • Only females have nidamental gland that secretes outer shell of egg.

  42. 5. Eggs are deposited in string-like masses in octopus den. • Octopus brood young until they hatch. Keeping clean of debris. • Young never cared for after hatching.

  43. Cecum • Fin • Testis • Vena Cava • Branchial heart • Gill • Ink sac • Funnel • Tentacle • Arms • Eye • Intestine • Penis • mantle

  44. Economic/Environmental Significance • 1. Food source- calamari, octopus • 2. Bait for commercial fishermen • 3. Can be pests in oyster beds- eating up all profit! • 4. Cephalotoxin may be used for medicine/research

  45. The Giant Squid • 50 feet long & weigh almost 1 ton • Eats fish & other squid and has been known to eat sperm whale calves

  46. Journal • Octopus do not have a shell. Describe all methods they have to protect themselves since they don’t have a shell.

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