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Phylum Porifera

Phylum Porifera. Porifera Characteristics. Freshwater and marine Simplest of all animals Asymmetrical No systems for repro, digestion, respiration, sensory, excretion. Porifera Characteristics. ~ 5,500 extant species Highest abundance in unpolluted littoral and tropical reefs

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Phylum Porifera

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  1. Phylum Porifera

  2. Porifera Characteristics • Freshwater and marine • Simplest of all animals • Asymmetrical • No systems for repro, digestion, respiration, sensory, excretion

  3. Porifera Characteristics • ~ 5,500 extant species • Highest abundance in unpolluted littoral and tropical reefs • ~ 75% benthic biomass

  4. Porifera Characteristics • Sessile (Adults) • Suspension-feeders (Adults) • Multicellular • Flagellated cells = choanocytes circulate water through water canals • No tissues • Cells totipotent

  5. Porifera Characteristics • Outer and inner cell layers lack basement membrane • Middle layer (mesohyl) has motile cells and skeletal material • Skeletal elements (when present) are calcium carbonate, silicon dioxide and/or collagen fibers

  6. Taxonomy and classification • Taxonomy based on skeletal elements • Now embryological, biochemical, histological, and cytological methods to diagnose sponge taxa

  7. Three classes (Calcarea, Demospongiae, Hexactinellida) • Class Calcarea: Calcareous sponges • Shallow, tropical water, near shore Leucetta

  8. Class Calcarea • Spicules = calcium carbonate • Calcarean spicules lack hollow canals = strong Clathrina

  9. Class Hexactinellida (Glass sponges) • Silica spicules • Spicules join at right angles, sponge appears artificial

  10. Class Demospongiae (Demosponges) • Largest and most diverse class of sponges, ~ 90 percent of sponges • Spicules either spongin, an organic substance; or silica, a mineralized substance Oscarella

  11. Class Demospongiae • Genera Adocia, Halisarca, Myxilla

  12. Aquiferous system • Brings water to cells • 1 x 10 cm sponge pumps 22.5 l water daily • Large sponge filters body mass every 10-20 s

  13. Sponges are single individuals • Grow by continually adding cells that differentiate as needed

  14. Body structure and aquiferous System Outer layer • Perforated by small holes - dermal pores or ostia • Choanoderm: innermost layer of flagellated cells = choanocytes • Mesohyl: middle layer

  15. Body structure: 3 shapes

  16. Asconoid sponges • Asconoid: one-cell thick choanoderm is simple and continuous • ~10 cm height • Thin walls enclose central cavity; atrium opens outside via osculum • Pinacoderm has specialized cells; porocytes • External opening of porocyte canal is ostium or incurrent pore

  17. Asconoid sponges

  18. Syconoid sponges • Syconoid: choanoderm folded • Mesohyl two layers thick: • Outer region is cortex (contains skeletal material)

  19. Leuconoid Sponge • Leuconoid: choanoderm subdivided into separate flagellated chambers

  20. Flow rate • Flow rate not uniform throughout • Water must move slowly over choanoderm • Exchange nutrients, gases, and wastes • Water leaving osculum must be carried far enough away to prevent fouling

  21. Cells that line surfaces • Pinacocytes • Porocytes • Choanocytes

  22. Cells that line surfaces • Porocytes • Form ostia • Cylindrical tube-like cells • Contractile - open and close pore to regulate diameter

  23. Cells that line the surface • Choanocytes • = choanoderm • Create currents • Not coordinated in movement

  24. Cells that secrete skeleton • Fibrillar collagen • Collencytes • Lophocytes • Spongocytes • Calcareous and siliceous spicules • Sclerocytes

  25. Contractile cells • Myocytes • Contractile cells • Filament arrangement homologous with smooth muscle cell • Unlike neurons and true muscle fibers

  26. Cell Aggregation • Atlantic sponge (Microcionaprolifera) • Pieces pressed through fine cloth • Separated cells reorganize • 2-3 weeks • Self-recognition

  27. Support • Skeletal elements • Organic - collagenous • Inorganic – siliceous (hydrate silicon dioxide) • Sponges only animals that use hydrated silica as skeletal material

  28. Sponge Harvest • Harvested for thousands of years • Greeks harvested sponges • Sponge fishery south of FL, Bahamas, Mediterranean • 1938: 2.6 million lbs

  29. Sponge Harvest • Hippospongia • Spongia

  30. Spicules • Microscleres • Megascleres • Demosponges and Hexactinellids have both • Calcareous sponges have only megascleres

  31. Nutrition, Excretion, and Gas Exchange • Intracellular digestion • Continuously circulate water • Size selective feeders • Food capture • Phagocytosis and pinocytosis

  32. Excretion • Ammonia and gas exchange • Diffusion

  33. Activity and Sensitivity • Respond to environmental stimuli: • Close ostia or oscula, canal constriction, backflow

  34. Reproduction and Development • Sexual and asexual reproduction • All sponges capable of sexual and asexual repro • Processes unknown due to lack of distinct, localized gonads (gametes, embryos occur throughout mesohyl) • Asynchrony of reproductive activity w/in populations

  35. Reproduction and Development • Asexual Reproduction • All sponges produce viable adults from fragments • Cellular reorganization “pinches off” branch ends which regenerate into new adults – branching species

  36. Reproduction and Development • Asexual Reproduction • Common in Florida’s sponge farms - cuttings attached to cement structure • Other processes include formation of gemmules, budding

  37. Reproduction and Development • Gemmules • Produced in winter as dormant bodies • Coat and supportive cells protects from freezing and desiccation

  38. Reproduction and Development • Gemmules

  39. Reproduction and Development • Budding • Squat or elongate club-shaped protrusions from sponge surface • Buds drop, carried by current, adhere to substratum • Marine species

  40. Reproduction and Development • Sexual Processes • Majority are hermaphroditic; produce sperm and eggs at different times • = Sequential hermaphroditism • Protogyny or protandry may occur once or many times during life

  41. Reproduction and Development • Sexual reproduction • Sperm from choanocytes; eggs from choanocytes and archaeocytes

  42. Reproduction and Development • Sexual process (Demospongiae and Calcarea) • Sperm and oocytes released into environment via aquiferous system • Sperm release -”smoking sponges” • Fertilization in open water (oviparous) • Few viviparous: sperm into nearby sponge’s aquiferous system; sperm to oocyte for fertilization

  43. Reproduction and Development Madsen sponge releasing sperm

  44. Reproduction and Development • Release of larvae (vivipary) • Through aquiferous system or ruptured wall • Larvae swim hours or days, or crawl along substratum before settling • Larvae are lecithotrophic = use stored yolk

  45. Reproduction and Development • Larval development

  46. Distribution and Ecology • Calcareous sponges abundant in shallow waters < 200 m • Hexactinellids deeper • Demosponges at all depths

  47. Distribution and Ecology • Sensitive to suspended sediments • Resistant to hydrocarbon and heavy metal contamination • Why?

  48. Symbioses • Commensalism common (small inverts, fishes) • Protection, habitat, water currents for suspended food particles • Some organisms utilize sponge for camouflage, small piece on shell or carapace

  49. Boring Demosponges - harmful to corals and mollusc shells • = bioerosion; chemical and mechanical removal of fragments by etching cells

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