Simple Invertebrates Sponges, Cnidarians, Flatworms, Roundworms

1. Simple InvertebratesSponges, Cnidarians, Flatworms, Roundworms Chapter 23.3

2. Sponges

3. Sponges • Unlike other animals • Once classified as plants • Sessile • Don’t move • Attached • Lack symmetry • Lack tissues

4. Favorite Sponges • What is wrong with the image?

5. Sponge Size • Varies • Depends on current velocity and space • Encrusting sponges • Small (< 1 cm dia.) • Upright sponges • Larger ( 2 m dia.)

6. Sponge Classification • Phylum Porifera • “Pore bearer” • Ostia • Many small openings • Water enters • Cover body • Oscula • Larger openings • Water exits

7. Sponges • All aquatic • Few freshwater species • Most marine • Most bag-shaped • Large internal cavity • All filter feeders • Pump water through body • Filter small particles from water

8. Sponge Bodies • Simplest animals • No tissues • Only two cell layers • Jellylike substance around cells = mesohyl • Cell recognition

9. Sponge Cells • Perform all functions • Four types: • Epithelial cells • Choanocytes • Amoebocytes • Porocytes

10. Sponge Cell Layers spicule mesohyl • two cell layers thick with a connective tissue layer in between, the mesohyl (dark blue pattern) pinaco- cytes • The outer layer composed of pinacocytes (eipthelial layer in lab) (baby blue) amebo- cytes - The inner layer are the choanocytes (peach, black). choanocytes • Mesohyl which contains spicules, amebocytes, etc… EXTERIOR | INTERIOR

11. Filter Feeding • Choanocytes • “Collar cells” • Line central cavity • Spongocoel • Flagellated • Create currents

12. Filter Feeding • Choanocytes • Act as sieves • Trap plankton • Pulled into cell • Digested intracellularly • Wastes expelled

13. Epithelial Cells • Epithelial cells • Thin and flat • Surface cells • Pinacocytes • Respond to touch and chemicals • Can close pores

14. Simple Digestion • Digested within the cell • Nutrients released into mesohyl • Middle layer • Contains spicules and amoebocytes

15. Amoebocytes • Amoeba-shaped cells • Blob-like • Move like an amoeba • Between cell layers of sponge • Function to carry nutrients to other cells • Carry away wastes • Aid in reproduction • Produce chemicals to make spicules

16. Pore Cells • Porocytes • Megaphone shaped • Single cell around each pore • Create the openings • Can close • Regulate water flow • sponge feeding 5:22

17. Sponge Skeletons • Provides framework and support • Gives general shape • Used to classify • Made of: • Calcium carbonate • Silica • Protein = spongin

18. Spicules • Not cells – not living • Small needle-like structures • Composed of silica or calcium • Located between cell layers in mesohyl • Function in support • Produced by other cells

19. Spongin • Protein • Tough fibrous network • Flexible • Skeleton of bath sponges

20. Review Structure

21. Sponge Body Wall

22. Feeding Review

24. Diversity of Sponges • Three classes: • 1) Demosponges • 2) Calcareous sponges • 3) Hexactinellida

25. Classes of Sponges • 1) Class Demospongiae • Largest goup • Ninty percent • Bath sponges • No spicules – just spongin • Soft to the touch

26. Classes of Sponges • 2) Class Calcarea • Most primative • Shallow water species • Spicules of calcium carbonate • Hard • “rock sponges”

27. Classes of Sponges • 3) Class Hexactinellida • Small group • Skeletons of silicon oxides • “Glass sponges" • Deep-water forms • Ex: Venus'-flower-basket • In Japan Venus'-flower-baskets • Given as wedding presents to symbolize lifelong devotion and fidelity

28. Classification of Sponges • Based on canal systems: • Asconoid • Syconoid • Leuconoid

29. Sponge Reproduction • Asexual • Regeneration • Cut pieces grow into new sponges • Budding • Copies grow off original

30. Asexual Reproduction • Gemmules • Freshwater sponges • Encased amoebocyte cells • Withstand drought or freezing • Hatch to form new sponges

31. Sponge Reproduction • Sexual • Also common • Most are hermaphrodites • Produce both egg and sperm • Different times to avoid self-fertilization • Spawning

32. Sponge Reproduction • Fertilization • Sperm released • Moves through water and enters pore • Collar cells pass it to mesohyl • Fertilizes egg here

33. Sponge Development • Fertilized egg develops into larva • Brief free-swimming stage • Attaches and grows into sponge

34. Sponges and Humans • Bath sponges • Harvested for our use • Biomedical compounds • Have antimitotic properties • Stunt growth of cancer cells • Indicators of environmental health • WI distribution is down

35. Cnidarians

36. Cnidarian Classification • Domain = Eukarya • Kingdom = Animalia • Phylum = Cnidaria • Four classes: • Hydrozoa • Scyphozoa • Anthozoa • Cubozoa (box jellies)

38. Cnidarians • Simple animals • More advanced than sponges • Have specialized tissues • Two layers of cells • Ectoderm • Endoderm • Middle layer of mesoglea

39. Cnidarian Characteristics • Tissue layers = 2 • No organs • Radial symmetry • Cnidocytes • Tentacles • Feeding and grasping • Extracellular digestion

40. Cnidarian Body Forms • Two basic types: • Medusa • Free floating • Umbrella-shaped • Mouth below • Tentacles hang down • Polyp • Attached • Vase-shaped • Mouth upward • Tentacles upward

41. Body Forms

42. Cnidocytes • Stinging Cells • Distinguishing trait • Cnidaria • From Greek “cnidos” = Stinging nettle • Contain nematocysts • Small barbed harpoon • Explode forcefully • May contain toxins

43. Cnidocyte Function

44. Extracellular Digestion • Outside cell • Food can be larger than cell • Gastrovascular cavity • Central cavity • Breaks food down • One opening

45. Recall Cnidarian Classification: • Domain = Eukarya • Kingdom = Animalia • Phylum = Cnidaria • Four classes: • Hydrozoa • Scyphozoa • Anthozoa • Cubozoa (box jellies)

46. 1) Class Hydrozoa • Most primitive cnidarians • Most are colonial and marine • Polyp and medusa stages

47. Ex: Hydra • Freshwater • Unique • No medusa stage • Attach by basal disk • Reproduce asexually or sexually • Studied in schools

48. Hydra Anatomy

49. Hydra Anatomy

50. Hydra Feeding • Hydra in pond water • Hydra feeding