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BIOL 201 Chp 5 Porifera and Placozoa
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BIOL 201 Chp 5 Porifera and Placozoa



This is a lecture presentation for my BIOL 201 Invertebrate Zoology students on Chapter 5: Porifera and Placozoa (Invertebrate Zoology, 7th Ed. by Ruppert, Fox, & Barnes, 2004)....

This is a lecture presentation for my BIOL 201 Invertebrate Zoology students on Chapter 5: Porifera and Placozoa (Invertebrate Zoology, 7th Ed. by Ruppert, Fox, & Barnes, 2004).

Rob Swatski, Assistant Professor of Biology, Harrisburg Area Community College - York Campus, York, PA.
Email: rjswatsk@hacc.edu

Please visit my website, BioGeekiWiki, for more biology learning resources: http://robswatskibiology.wetpaint.com

Visit my Flickr photostream for anatomy model photographs!

Thanks for looking!



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    BIOL 201 Chp 5 Porifera and Placozoa BIOL 201 Chp 5 Porifera and Placozoa Presentation Transcript

    • Chapter 5: Porifera & PlacozoaBIOL 201: Rob Swatski Asst. Prof. BiologyInvertebrate Zoology HACC-York 1
    • PhylumPoriferaPorifera = the “pore- bearing” spongesNot considered to be eumetazoansPosses epithelioid & rudimentary connective tissue Lack true muscle & nervous tissues 2
    • PoriferaOverview 8000 species, most marine, 150 FW Primitive, sessile filter feeders Most asymmetrical, but some display radial symmetry Erect, branching, or encrusting on substratum 3
    • Sponge Body PlansAsconoid Syconoid Leuconoid 4
    • AsconoidSponges Simplest body plan: hollow tube with base attached to substrate Ex: Leucosolenia Have 1 large spongocoel (atrium) lined with 1 layer of choanoderm Choanocytes beat & draw water through ostia (aquiferous system) 5
    • AsconoidSponges, cont. Water exits spongocoel through single large osculumSmallest & thinnest of all sponges (1 mm diameter) Growth imited by spongocoel diameter If they had larger diameters, their body volume would exceed pumping capacity of choanoderm 6
    • SyconoidSponges Body wall has incurrent canals & outpockets (radial canals or choanocyte chambers) lined with choanodermIncreases choanoderm SA & decreases spongocoel volume Larger than asconoidsponges (several cm), with thicker body wallsGrantia & Sycon (Scypha) 7
    • Syconoid sponge(Sycon) 8
    • Leuconoid Sponges Contains 1000’s of choanocyte chambers, further increasing choanoderm SA Smaller excurrent canals further reduce spongocoel diameter The largest sponges (several cm – 1+ m), with the thickest body walls; indeterminate growth May have more than one osculum 9
    • 10 Leuconoid sponge
    • 11
    • Structure ofSponge Body Wall Classified as either cellular or syncytial Cellular sponges have 2 primitive primary tissues: epithelioid & mesohyl Epithelioid tissue resembles epithelium Mesohyl: middle CT layer of fibrous ECM 12
    • Epithelioid Tissue Pinacoderm Choanoderm Covers outer body & lines Flagellated cells with a inner chambers (around collar of microvilli choanoderm)Pinacoytes Porocytes Choanocytes 13
    • 14
    • Mesohyl Tissue (all cells are dynamic, totipotent & amoeboid) Archeocytes Lophocytes Spongocytes Can differentiate into Produce thick Secrete & maintainany sponge cell; aide in skeletal spongin collagen fibersdigestion (phagocytosis) fibers & internal transport 15
    • 16
    • Mesohyl Tissue, cont. Sclerocytes Myocytes Germ cells Muscle-like cells Reproductive Secrete spicules: around osculum that cells: oocytes &skeletal elements made constrict or dilate to spermatocytes of silica or calcium control water flow 17
    • FW Leuconoidsponge 18
    • Syncytial Sponges Contain simpler, No pinacoderm & Collar bodies are Mesohyl withreduced cells in a choanoderm; have located archeocytes, syncytium, a collar bodies individually in sclerocytes, & continuous instead collar body germ cells cytoplasm that chambers (not inlacks membranes epithelioid sheets) 19
    • SyncytialSponges, cont. Body wall resembles 3-D cobweb-likepattern: trabecular syncytium Each strand of the trabecularsyncytium encloses an axis of mesohylContains collagen & spicules 20
    • Porifera TaxonomySP Symplasma Subphylum Cellularia(Hexactinellida) (Cellular Sponges) Class Class Glass Demospongiae: sponges: Calcarea: 80% of all sponges; calcareous syncytial siliceous spicules & spicules spongin 21
    • Glass Sponge(SP Symplasma) 22
    • SP Cellularia23 (Class Demospongiae)
    • SP Cellularia(Class Calcarea) 24
    • SP Cellularia(Class Calcarea) 25
    • SpongeSkeletonDiverse mesohyl actsas an endoskeletonSome skeletons have fine collagen fibers onlyMay contain spicules, spongin, or bothIncredible diversity ofspicules: some project through mesohyl to protect outer sponge body 26
    • 27
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    • WaterPumping Most pump a watervolume equal to theirbody volume every 5 seconds Large SA & flowregulation slows down velocity Contract or relax myocytes to adjust osculum diameterCan also close ostia &adjust flagellar beat of choanoderm & collar bodies 30
    • 31
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    • Locomotion Some have limited ability to move (1-4 mm per day) Result of collective amoeboid movement of cells: very dynamic mesohyl environment (remodeling) Osculum contraction by myocytes Whole body contraction 33
    • Nutrition Filter feeders able to phagocytize food <50µm (dinoflagellates, bacteria, viruses, debris)Some are carnivores &don’t filter; trap small animals such as crustaceans Choanocytes transfer particles to vacuoles for digestion Archeocytes remove wastes & inorganics from system 34
    • 35
    • SymbioticRelationships Some have PSN endosymbionts: cyanobacteria, dinoflagellates, chlorophytes Symbionts help create the bright colors of sponges Sponges must live in shallow water for PSN Some obtain up to 80% of nutrients from photosynthate 36
    • InternalTransportGas & waste transport via simple diffusionSponges are “leaky,” sowater penetrates their entire bodySheets of cells are only 1 cell layer thickMobile amoeboid cells 37
    • InternalTransport, cont. Ammonia is the main metabolic waste Common nitrogenous waste in aquatic environments Archeocytes transfer wastes & nutrients Some individual cells posses contractile vacuoles 38
    • Nervous Tissue Lack nerve cellsSome have localized action potentials responsible formyocyte contraction Glass sponges generate AP’s thattravel rapidly across their syncytium Used to stop flagellar beating 39
    • SpongeEcology Many producetoxins to prevent predation Food for spongivores:nudibranchs, fish, turtles Hawksbill turtlefeces can be up to 95% siliceous spicules! Some releasechemicals that kill sessile competitors (corals ) 40
    • 41
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    • SpongeEcology, cont.Habitat for animals(shrimps & brittle stars) Decorator crabs place sponges ontheir carapaces for defense & glidingCliona breaks down calcareous shellsBores into shells for protection 43
    • 44
    • Reproduction Clonal reproduction via fragmentation & budding Sponges display incredible powers of regeneration Reproduce as a response to wave damage or grazing Gemmules: spore-like masses of nutrient- rich archeocytes enclosed by a shell; undergo diapause 45
    • Reproduction, cont. Sponges frequently reproduce sexually Hermaphrodites (monoecious) Germ cells occur throughout mesohyl Choanocytes can also release sperm & form eggs 46
    • Reproduction, cont. Sperm are broadcasted into water column Choanocytes phagocytize incoming sperm, but don’t digest them Choanocytes differentiate into an amoeboid cell & deliver sperm head to egg Most eggs fertilized via phagocytosis (most sponge sperm lack an acrosome) 47
    • Reproduction, cont. Some sponges are oviparous: release zygotes into water column Most are viviparous: retain zygotes within body Release larvae at a later period Sponge larvae are very diverse: coeloblastula, amphiblastula, parenchymella 48
    • 49
    • Reproduction, cont. Larvae are short-lived, settle in a few days, & creep across substrate until suitable spot is found Metamorphose into a juvenile Varied lifespan: live several years in temperate waters; 200+ years in tropics or deep sea Some only grow 0.2 mm/yr & could be 5000 years old with constant growth rate 50
    • PhylumPlacozoaTrichoplax: superficiallyresembles large ameba (2-3 mm diameter) Upper & lower cell layers, 25 µm thickEnclosed by single layer of epithelioid cellsDensely ciliated ventralsurface for locomotion 51
    • PhylumPlacozoa, cont. Fiber syncytium: CT layer of watery ECM & syncytial network; contractile Resembles ameba in form & locomotion as it glides across substratum Feeds on algae via extracellular digestion Reproduces asexually via budding & fragmentation; sexual repro & larvae unknown 52
    • PlacozoanPhylogeny Early evolutionary line of simple metazoans Intermediate between sponges & cnidarians (RNA sequence data)Resembles hypothetical protometazoanEpithelioid layer is moresimilar to true epithelial tissue 53
    • Credits by Rob Swatski, 2010 Visit my website for more Biology study resources! http://robswatskibiology.wetpaint.com http://www.flickr.com/photos/rswatskiPlease send your comments and feedback to: rjswatsk@hacc.edu This work bears an Attribution-Noncommercial Share Alike Creative Commons license. 54