1 / 65

Chapter 12 Molluscs

Chapter 12 Molluscs. octopus. snail. clam. slug. chiton. scallop. cuttlefish. Nautilus. Giant squid Architeuthis. Phylum Mollusca. molluscus = “soft body” ~ 100,000 species diverse Size: < 1 cm  18 m long. Characteristics of Phylum Mollusca. Wide variety of habitats

byron
Download Presentation

Chapter 12 Molluscs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 12Molluscs

  2. octopus snail clam slug chiton scallop cuttlefish Nautilus Giant squid Architeuthis Phylum Mollusca • molluscus= “soft body” • ~ 100,000 species • diverse • Size: < 1 cm  18 m long

  3. Characteristics of Phylum Mollusca • Wide variety of habitats • Tropics  polar seas • Most are marine, some freshwater, some terrestrial Giant clam

  4. (Endoderm) (mesoderm) Characteristics of Phylum Mollusca • Eucoelomates • True coelom, lined with mesodermal peritoneum (membrane that lines coelom, covers coelomic viscera) • mesentery- mesodermal sheet that suspends internal organs in coelom • Schizocoelous • Coelom forms by splitting of mesodermal bands (next slide)

  5. Fig. 9-13, p188

  6. Characteristics of Phylum Mollusca • Unsegmented • closest common ancestor shared with segmented worms (Phylum Annelida) (ie. earthworms)

  7. Squid Freshwater clam Characteristics of Phylum Mollusca • All organ systems are present, well-developed • Respiratory organs • Circulatory system, with heart • Greater body size possible

  8. Molluscan body form 2-part body plan: • Head-foot • Visceral mass Octopus

  9. Snail radula Head-foot Head: • anterior • Cephalic sensory organs • Feeding organs: Radula • Most molluscs (not bivalves) • rasping structure • Tongue-like • Rows backward-pointing “teeth” • Scraping food • drilling

  10. Mollusk Body Plan

  11. Octopus http://acolyte.org/images/octopus.png Head-foot Foot: • ventral • Muscular structure • Locomotion • Attachment • modifications

  12. Chiton Visceral mass • Digestive organs • Reproductive organs • Circulatory organs • Respiratory organs Mantle • Attached to visceral mass • Dorsal skin folds • protective • In some, mantle secretes protective shell over visceral mass

  13. Mantle cavity • Space between mantle and foot • Opens to outside • Functions: • Gas exchange (respiration) • Excretion/elimination • Release reproductive products

  14. Circulatory system of molluscs • Open circulatory system (except Class Cephalopoda) • Open circulatory system • heart pumps hemolymph (blood) through body cavity, b/w cells • No small blood vessels

  15. Circulatory system of molluscs • Closed circulatory system (Class Cephalopoda)= • Blood confined to vessels

  16. Video clip- aquatic snail (note heart)

  17. Long-finned squid-Loligo http://www.biology.ualberta.ca/courses.hp/zool250/Labs/Lab08/Lab08.htm Molluscan reproduction • Mostly dioecious Giant squid

  18. Classes of Molluscs • Class Polyplacophora • Class Scaphopoda • Class Gastropoda • Class Bivalvia • Class Cephalopoda • Others…

  19. Chiton Underside of chiton Classes of Mollusc Class Polyplacophora • “many plate-bearers” • Chitons • Dorsoventrally flattened • Shell= 8 overlapping dorsal plates • marine

  20. http://www.ucmp.berkeley.edu/mollusca/scaphs/scaphopoda.html Class Scaphopoda • Tooth shells • Long, slender body • Burrows into mud • Shell open at both ends

  21. Pulmonate snail Silver cloud nudibranch Limpet Class Gastropoda Gastro= gut • Poda= foot • Snails, limpets, slugs, whelks, cone snails, conchs, periwinkles, abalone, sea slugs…. • Largest class • Most diverse • Marine, freshwater, terrestrial

  22. Class Gastropoda (cont’d) • Microscopic  1m long (sea hare) • Typically 1-8cm long

  23. Class Gastropoda (cont’d) • Basically bilateral • Visceral mass, mantle, mantle cavity undergoes torsion (twisting) asymmetrical

  24. Class Gastropoda (cont’d) • Moves mantle cavity, w. gills, anus, visceral organs to anterior

  25. Class Gastropoda (cont’d) Why torsion? • Head withdraws into shell first • Clean, undisturbed H2O enters mantle cavity

  26. Coiling • Absent in some • Visceral mass/mantle may be coiled • Successive coils- whorls • Caused pressure on right side  adaptation: loss of rt. kidney, auricle, gill • Water enters via left, leaves right

  27. Class Gastropoda (cont’d) • May have protective shell

  28. Class Gastropoda • Well-developed sense organs • Eyes at base or at end of tentacles

  29. Gastropod feeding habits: • Herbivores • Carnivores http://eebweb.arizona.edu/collections/Fishes/Photographs.htm Red abalone Moon snail- uses radula to drill holes in bivalve (ie. clams)

  30. Land snail • Food for humans

  31. Cone snail Barbed radula tooth containing neurotoxin- powerful analgesic Cone snail • Marine • Venomous • Contain analgesic Video Eating fish Nat Geo Cone snail

  32. Abalone • Several holes in top of shell • Excrete waste • Food for humans

  33. Slug • No shell • Garden pest

  34. Limpets • Cling to rocks or other surfaces

  35. Conch • Large shell • Marine • herbivores Human impact Feeding on ocean floor

  36. Giant clam California mussel Class Bivalvia • clams, oysters, mussels, scallops • soft body between two halves of a hinged shell

  37. Class Bivalvia (cont’d) • Aquatic • most marine, some fresh water • no tentacles, head, radula • adductor muscle • Large cilia-covered gills (in most)

  38. Bivalve shell morphology Umbo- oldest part of shell • Growth in concentric lines around it

  39. Valves open by adductor muscle • contraction= closed • relaxing= open • Hinge= mantle secretion of more protein, less calcium carbonate

  40. Water movement through bivalves • incurrent siphon - water into the mantle cavity • water circulates over the gills • Gas exchange • Filter feeding

  41. Water movement through bivalves (cont’d) • water flows past anus where waste is excreted • excurrent siphon – water out of the mantle cavity

  42. Locomotion • Mostly sedentary/sessile • highly developed muscular foot • often to burrow into sediment • move by slicing-like motion of foot • swim by chattering motion of shell (scallops) • Clams not just for chowder movie

  43. http://www.csc.noaa.gov/scoysters/images/bio/oysters2.jpg Oyster • lower valve is cemented to any object available • Improve water quality • Decrease bank erosion • food

  44. Shell Epithelium Developing pearl Pearl Production • protective function • foreign substance between mantle & shell • mantle secretes pearly layers of nacre around substance

  45. Zebra mussel • Environmental Pest • Ballast water of ships from Europe in 1986 Zebra mussel

  46. Zebra Mussels (cont’d) • attach to any hard substrate • Other mussels, clams, crayfish water pipes, docks, boats • Outcompete other bivalves

  47. Zebra Mussels (cont’d) • Live in high densities • Reproduce rapidly Lake Michigan http://epod.usra.edu/archive/epodviewer.php3?oid=135264

  48. Zebra Mussels (cont’d) • Killed all native mussels in Lake Erie

More Related