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BIOL 201 Chp 7 Cnidaria
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BIOL 201 Chp 7 Cnidaria

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

This is a lecture presentation for my BIOL 201 Invertebrate Zoology students on Chapter 7: Cnidaria (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!
http://www.flickr.com/photos/rswatski/

Thanks for looking!

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  • 1. Chapter 7: CnidariaBIOL 201: Rob Swatski Asst. Prof. BiologyInvertebrate Zoology HACC-York
  • 2. PhylumCnidaria Hydra, anemones, stony & soft corals,hydroids, & jellyfishesMost marine (10,000sp); few FW (20 sp); no terrestrial sp Colonial or solitaryCorals build reefs (#2 biodiversity) 2
  • 3. CnidariaStructure & Function Cnidocytes! Body plan resembles gastrula; mouth surrounded by tentacles Coelenteron (Gastrovascular cavity, GVC) Radial symmetry around oral-aboral axis: advantage? 3
  • 4. Body Forms Polyp Medusa Sessile &Resembles Pedal disc Umbrella Manubrium: benthic; “Mouth- flower & & oral or bell- “elephant “mouth- down” stem disc shaped trunk” up” 4
  • 5. 5
  • 6. 6
  • 7. 7
  • 8. 3 Tissue LayersEpidermis: epithelium Gastrodermis: epitheliumMesoglea (gelatinous ECM): CT Diploblastic 8
  • 9. ColonialCnidarians Reproduce via budding, but buds don’t separate Produce zooids that resemble juveniles Small zooids have large SA:V Fillter-feeding: many mouths & tentacles, broad distribution, small size 9
  • 10. Types ofColonies Stolonate: have stolons (strawberry runners) Coenosarc: have coenosarc & solenia (hollow tubes) Fruticose: upright & branching; plantlike or featheryBudding: fixed-length(Obelia) & axial-polyp 10
  • 11. 11
  • 12. CnidarianSkeletons More diverse than sponges Exoskeletons: chitinous periderm (hydrozoans); calcium carbonate (stony corals); shellfragments (anemones)Endoskeletons: fibers& spicules (soft corals) or cell columns with turgid vacuoles (hydrozoans)Hydrostatic skeletons: Hydra, anemones 12
  • 13. Musculature Antagonistic sheets of muscle Circular smooth muscle in gastrodermis Longitudinal smooth muscle in epidermis Coronal muscles around medusa subumbrella 13
  • 14. Diversity ofMovement Polyps: shorten, extend, & bend Medusae: constrict bells for swimming Some polyps inch- worm & somersault! Tentacles move for prey manipulation Subumbrella retracts in polyps & medusae 14
  • 15. 15
  • 16. NervousSystems Two nerve nets:base of epidermis &gastrodermis; joined by nerve bridges across mesogleaNerve impulses cantravel any direction (radial sensory system) Medusae: nerverings, musculature, ganglia, & senseorgans around bell Statocysts, ocelli,chemoreceptors, &mechanoreceptors 16
  • 17. Cnidocytes Used for prey capture & defense Cnidocytes (cells) contain cnida (fluid- filled capsule with tubule) Nematocytes contain nematocyst that stings & releases toxins Spirocytes contain spirocyst that contains sticky threads for adhesion 17
  • 18. Cnidocytes, cont. Cnidocytes: abundant in epidermis, on tentacles, in gastrodermis Chemical & mechanical cues from prey trigger firing of nematocyst Toxins interfere with Na+/K+ pumps or degrade cell membranes Hydra discharges 25% of nematocysts eating 1 brine shrimp (replaced in 24hr) 18
  • 19. 19
  • 20. Nutrition & Internal Transport Coelenteron (GVC): blind gut Septa increase SA for digestion, absorption, gas exchange, excretion, repro, hydrostatic skeleton Radial & ring canals in medusae radiate out from central stomach Coelenteron often branches into each tentacle 20
  • 21. 21
  • 22. FeedingPrey is caught, mouthopens, tentacles stuff prey inside, & enzymes digest extracellularyGastrodermis absorbs nutrients & largerparticles are digested intracellularlySlow process, taking several days Wastes ejected out through mouth 22
  • 23. Nutrition &Circulation Many species have PSN endosymbionts May account for 90% of nutrition in some species Often defined patterns of fluid circulation around coelenteron Ciliated gastrodermis; muscular contractions 23
  • 24. Gas & WasteExchange Gas exchange occurs across general body surfaces: tentacles, body wall Waste exchange (excretion) occurs across body wall Ammonia is primary waste product Terrestrial inverts are adapted for conserving water during excretion 24
  • 25. GeneralReproduction Amazing regenerators! Can lose oral end & regrow it Anemones can fully recover from dissections Clonal reproduction is common in polyps, but less common in medusae 25
  • 26. 26
  • 27. SexualReproduction Sexual repro in most: some monoecious (hermaphroditic); most dioecious Germ cells develop in gastrodermis & gametes released into coelenteron Most have external fertilization; some internal fertilization Zygote develops into planula larva, settles with aboral end down, & develops into juvenile polyp 27
  • 28. ClassAnthozoa “Flower animals”Sea anemones, corals, sea fans, & sea pensLargest class: 6000 sp; solitary or colonialNo medusa phase in lifecycle 28
  • 29. AnthozoanBody Form Long pharynx attached to coelenteron Many septa, 6-192 depending on species size Some have acontia: stringy filaments attached near septa base Heavily armed: spew from mouth as anemone deflates 29
  • 30. Musculature Mostly epidermal & gastrodermal epitheliomuscular cells Epidermal musculature: controls tentacles & oral disc Gastrodermal musculature: controls body column 30
  • 31. Retraction Controlled by retractors (longitudinal septal muscles) Tentacles & oral disc deflate & pulled into body Mesogleal sphincter muscle closes opening (draw-string) Must remove pump water out to retract; siphonoglyph cilia beat inwards to31 pump water back in
  • 32. Diversity of Class Anthozoa Subclass Subclass Alcyonaria Zoantharia (Octocorallia) (Hexacorallia) Order Order Order Order Order Gorgonacea: Pennatulacea: Stolonifera:Actiniaria: Scleractinia: sea fans, sea pens, organ pipeanemones stony corals whips, & feathers, & corals plumes pansies 32
  • 33. Subclass Zoantharia:Order Actiniaria Hexamarous symmetry: septa & tentacles in multiples of 6 Sea anemones: 1350 sp; brightly colored; most <10 cm Some have unique methods of locomotion Burrowing via peristalsis; walking on tentacles; swimming by thrashing tentacles 33
  • 34. OrderActiniaria: TraitsCarnivorous suspension feeders: mucus traps particles on tentacles, moved to mouth Photosynthate: mayhave 2 sets of tentacles: false for PSN (exposed during day) & true (exposed during night)Clonal repro via pedal lacerationGonads located in septa 34
  • 35. OrderActiniaria: Ecology Hermit crabs wear anemone on shell & will transfer to new shells Anemone gets substrate, food, protection, access to mates; Crab gets camouflage & protection Clownfish has protective surface mucus Anemone gets food, removal of sediment & necrotic tissue; Clownfish gets protection & food scraps 35
  • 36. SubclassZoantharia: OrderScleractinia Stony corals (3600 sp); close relation to anemones Secrete CaCO3 exoskeleton that can weigh tons Produce cups (corallites) that they retract into Most colonial polyps, 1-3mm diameter 36
  • 37. 37
  • 38. 38
  • 39. SubclassZoantharia: OrderScleractinia Corals are often very colorful due to PSN endosymbionts Algae often released in conjunction with gametes Coral bleaching can occur under stressful environmental conditions Incorrect light/UV intensity, salinity, temp (even 1°C) 39
  • 40. SubclassAlcyonaria: OrderStolonifera Octomerous symmetry: septa/tentacles in multiples of 8 Soft corals: don’t produce CaCO3; organ pipe corals Most lack nematocysts; secrete noxious chemicals to deter predators More tolerant of environmental fluctuations 40
  • 41. 41
  • 42. SubclassAlcyonaria: OrderGorgonacea Plant-like sea whips, fans, & plumes Highly branched Endoskeleton: axial rod made of gorgonin (highly cross-linked collagen) 42
  • 43. Subclass Alcyonaria: OrderPennatulacea Sea pens, feathers, & pansies 43
  • 44. Medusozoa Medusa phase in life cycle: planula  polyp  medusa Tetramerous radial symmetry: multiples of 4 Cnidae are all nematocysts 2 major classes: Scyphozoa (large jellies) & Hydrozoa (small jellies - Hydra, & hydroids) 44
  • 45. ClassScyphozoa 200 sp of large jellies Polyps: small & funnel-shaped (scyphistomae) Coelenteron divided by 4 septa Have 4 septal funnels that circulate water to gonads in adults 45
  • 46. 46
  • 47. ClassScyphozoa:Body Form Medusa bells: 2-40 cm diameter Manubrium divided into 4 oral arms Tentacles located around periphery of bell 47
  • 48. 48
  • 49. ClassScyphozoa:Body Form Coelenteron divided by septa into 4 gastric pockets 4 pairs of gonads in septa & 4 septal funnels Many have radial canals & marginal canals Gastrodermal cilia circulate water 49
  • 50. ClassScyphozoa:Body Form, cont. Lappets: rounded lobes on umbrella margin Rhopalia: sensory organs in grooves b/w lappets Statocysts: mechanoreceptors (also chemoreceptors & photoreceptors) Nerve net & nerve ring 50
  • 51. ScyphozoanReproduction Clonal: differentiate into strobila Stacked mini medusae separate via transverse fission (strobilation) Juvenile medusae are called ephyra Adult medusae reproduce sexually 51
  • 52. 52
  • 53. Scyphozoan Diversity: 5 OrdersSemaeostomeae Rhizostomeae Coronatae Cubomedusae Stauromedusae Aurelia Stomolophus Linuche Chironex Haliclystus 53
  • 54. ClassHydrozoaHydra & hydroids, firecorals, & Portugueseman-of-war; 3000 sp Most are colonies of polyp & medusa zooidsMedusa often form as buds, but are notreleased from colony Hydra life cycle does not include medusa phase 54
  • 55. HydrozoanBody Plans Two types of polyps: Athecate (A-form) & Thecate (L-form) Zooids 1mm or smaller in length Large SA:Vol No gastrodermal septa 55
  • 56. HydrozoanBody Plans Medusae arise from colony as lateral buds (not via strobilation) Velum: iris diaphragm on subumbrellar margin for swimming Hydroid colonies are sessile & benthic (seaweed- like) 3 colony forms: stolonate, coenosarcal, or fruticose 56
  • 57. Hydrozoan A-form Colonies Athecate: lack theca (protective cup) Periderm ends at attachment point of zooids Typically grow via axial- polyp budding 57
  • 58. Hydrozoan L-form Colonies Periderm forms a wine-glass shape theca Hydranth can retract into theca Theca may have a hinged lid (operculum) Grow via fixed-length budding 58
  • 59. ZooidTerminology Monomorphic colonies: 1 type of zooid Gastrozooids: feeding hydranths Polymorphic colonies: several types of zooids Gonozooids: reproductive polyps Dactylozooids: have nematocysts for protection & food capture 59
  • 60. 60
  • 61. Class Hydrozoa: Order Anthoathecatae Hydra: both clonal & sexual repro, but no medusa stage Fire corals: reef builders with nasty sting Velella: by-the-wind sailor with a float & sail; extreme polymorphism, with zooids suspended61 mouth-down Hydra
  • 62. Fire coral 62
  • 63. 63 Vellela: By-the-wind sailor
  • 64. Class Hydrozoa: Order Siphonophora Physalia: Portuguese man-of-war Pedal end of polyp bears a gas-filled float (pneumatophore) Buds arise from a column of polyp sets called cormidia (oldest near float) Possess diversity of zooids 64
  • 65. Physalia 65
  • 66. Class Hydrozoa: OrderLeptothecatae L-form hydroids: Obelia Feather-shaped colonies 66
  • 67. Class Hydrozoa: OrderLimnomedusae L-form hydroids with both polyp & medusa phase Gonionemus 67
  • 68. 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. 68