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Cnidaria and ctenophora 2012


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Cnidaria and ctenophora 2012

  1. 1. 1
  2. 2.  A metazoan Lineage ~700MY old Named after cindocytes – stinging cells  Most common type - nematocyst Body plan simple, sac-like  Symmetry is radial or biradial Aquatic - mostly marine, some freshwater species Show tissue level of organization 2
  3. 3.  Symmetry – radial  No “head”  Has oral & aboral ends Polymorphism present  Polyp (sessile) & medusa (free-swimming) body types Gastrovascular cavity  single opening (mouth/anus) surrounded by tentacles  H2O within serves as hydrostatic skeleton 3
  4. 4.  Stinging cell organelles, cnidae, prevalent on tentacles, epidermis, &/or gastrodermis  Nematocysts most abundant type Nerve net present, some sensory organs  Statocysts – balance organs  Ocelli – simple light sensors Muscle fibers present Reproduction  Asexual: budding (polyp)  Sexual: planula larvae (medusa, some polyp forms)  Individuals may be monoecious or dioecious No excretory or respiratory systems; diffusion suffices 4
  5. 5. Mouth & anus are the same opening Oral End ↓ Aboral End ↓ Oral End ↑ ←Pedal Disc Aboral End ↑Digestion extracellular in gastrovascular cavity; smaller particlesingested intracellularly 5
  6. 6.  Food source for mollusks & fish  Some ctenophores, mollusks, & flatworms will eat hydroids w/ nematocysts Habitats:  Coral reefs home to fish, arthropods  Hydroids attach to underwater structures Commensalism on mollusk shells Aquatic organisms provide food source for cnidarians Rarely provide food for human consumption 6
  7. 7. Polyp: hydroid form; Medusa: umbrellasessile; aboral end shaped; free-swimmingattached to substrate bypedal discBody tubular; mouth Body sac-like; mouthupward ringed by downward; tentaclestentacles ring umbrellaAsexual reproduction: Reproduction sexual &/budding, fission, pedal or asexuallaceration Medusa usuallySexual reproduction dioeciousoccurs tooSea anemones & corals Includes Scyphozoansare polyps – no medusa & CubozoansstageLocomotion: Hydras Locomotion: medusamove freely, polyps move freely about, atsessile, sea anemones mercy of wavesmove on basal disc 7
  8. 8.  Cnidarians mostly voracious carnivores, but predatory capabilities hampered by body plan. Polyps rely on stinging cells to capture/paralyze any organism the tide brings by Medusa rely on stinging cells to do same even though they are free-swimming (realize inability to totally control where they swim) 8
  9. 9. Stinging cells triggeredby mechanical orchemical stimuli 9
  10. 10. 10
  11. 11.  Cellgenerates osmotic pressure up to 140 atm that causes the ejection to occur Hydrostatic pressure increases as osmotic pressure decreases Due to high osmotic pressure, stimulus causes H2O to rush in opening operculum 11
  12. 12.  High hydrostatic pressure launches the thread within 3 milliseconds with an acceleration power of 40,000 g and a penetration force of 20-33 kPa; barbs point rear & anchor in victim’s tissue; poison injected Nematocysts are capable of penetrating up to a depth of 0.9 mm Lost nematocyst must be replaced 12
  13. 13.  While the amount of toxin expressed by a single nematocyst is minute, several thousand nematocysts discharging at once have a significant effect. Functionally, the toxin causes Na+ and Ca++ ion transport abnormalities, disrupts cellular membranes, releases inflammatory mediators, and acts as a direct toxin on the myocardium, nervous tissue, hepatic tissue, and kidneys. 13
  14. 14.  Specifically, the toxin may contain catecholamines, vasoactive amines (eg, histamine, serotonin), kinins, collagenases, hyaluronidases, proteases, phospholipases, fibrinolysins, dermatoneurotoxins, cardiotoxins, neurotoxins, nephrotoxins, myotoxins, and antigenic proteins. The protein component of the toxin tends to be heat labile, nondialyzable, and is degradable by proteolytic agents. 14
  15. 15.  United States Jellyfish stings occur most commonly during the summer along coastal regions. As the coastal population grows and more tourists come to the beaches, the frequency of jellyfish sting is likely to increase. One investigator reported 500,000 annual envenomations in the Chesapeake Bay area and 200,000 annually along the Florida coast. International Jellyfish stings occur in tropical oceans, especially between latitudes 30° south to 45° north, because of a high natural concentration of cnidarians. This is especially true of the east coast of Australia during the warm summer months between November and May. (Don’t forget, they’re in the southern hemisphere, so their summer is during our winter) 15
  16. 16. Jellyfish stings usually are mild, except those caused by species in the South Pacific, such as the box jellyfish or Portuguese man-of-war. Exact mortality and morbidity is not known because of underreporting and the lack of an international jellyfish sting registry. However, a recent epidemiology study of 118 cases of jellyfish stings from the Texas gulf coast showed 0.8% had no effect, 80.5% had minor effects, and 18.6% had moderate effects. 16
  17. 17.  Box jellyfish venom has a median lethal dose of 40 mcg/kg, which makes it the most potent marine toxin. The venom may kill a person weighing 70 kg within 3 minutes and is responsible for a mortality rate of 20%. Box jellyfish venom has caused 72 deaths secondary to respiratory paralysis, neuromuscular paralysis drowning, and cardiovascular collapse. 17
  18. 18.  The pain and spasms spread centrally as the venom travels to the central circulatory system, inducing parasympathetic overstimulation and respiratory-cardiac arrest. Most fatalities occur within 20 minutes of the envenomation; according to animal studies, approximately 5-10 mcg/kg of venom is required to induce cardiac arrest. 18
  19. 19.  The sting of the Portuguese man-of-war is more painful than a common jellyfish sting. It has been described as feeling like being struck by a lightning bolt, and some victims dread it more than a shark bite. This sting has been responsible for 2 reported deaths. 19
  20. 20.  The Arctic jellyfish is the largest, with tentacles reaching 200 ft, allowing the jellyfish to sweep an area slightly larger than a basketball court. 20
  21. 21.  Contains2 nerve nets at base of epidermis and gastrodermis which connect Nerve impulses carried by neurotransmitters via snapses  Transmission can go either direction  Lack myelin sheath around axons No brain, no centralized nervous system Sense organs simple  Statocysts & Ocelli 21
  22. 22.  The statocyst is a balance organ present in some aquatic invertebrates (Cnidarians,Ctenophores, Bilaterians). It consists of a sac-like structure containing a mineralized mass (statolith) and numerous innervated sensory hairs (setae). The statolith possesses inertia, causing the mass to move when accelerated. Deflection of setae by the statolith in response to gravity activates neurons, providing feedback to the animal on change in orientation and allowing balance to be maintained. Because organism has no “brain,” they are limited in their actions and responses to stimuli. The statocyst is therefore useful for telling the animal whether it is upside down or not. 22
  23. 23.  The phylum Cnidaria includes the first multicellular animals to form eyes; this group exhibits a diversity of eye designs ranging from a simple photosensitive sheet of cells to the complex image forming eyes of cubozoan jellyfish. Because of their basal position on the phylogenetic tree, cnidarians provide an excellent system in which to study the evolution of the first multicellular animal eyes and the evolution of photosensory mechanisms. 23
  24. 24.  The camera-type eyes of cubozoans represent the most highly evolved eyes in the Cnidaria.  Further they contain the visual pigments involved in phototransduction: rhodopsin and opsins.  These eyes resemble the proposed ancestral prototype eye. 24
  25. 25.  Class Hydrozoa:  Marine & freshwater, colonial, polyp & medusa forms Class Scyphozoa  Marine, most medusa forms Class Cubozoa  Marine, medusa form prominent, no known polyp forms, toxin lethal to humans Class Anthozoa  Marine, polyps only, no medusa form 25
  26. 26.  Hydra & Obelia are good examples of this class Hydra:  Freshwater species, 16 in N. America  Solitary polyps (typical form)  Eat larvae, worms, crustaceans  Asexual rep – budding;  Sexual Rep – prod of sperm/ova  Overwinter as cysts 26
  27. 27.  Colonyhas base, stalk, & terminal polyps (zooids)  Gastrozooids (feeding)  Gonophores (reproduction)  Dactylozooids (defense, tentacles) Eatcrustaceans, worms, larvae Buds remain attached, incr colony size  Medusa produced by asex. Budding, released Medusa – dioecious, reprod sexually  Planula larva attach, forming new colony 27
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  29. 29. 29
  30. 30.  Most “jellyfish” belong here Medusa body form Marine, free-swimming (mostly), open sea Aurelia example of scyphozoan Dioecious, fertilization internal, planula zygote Zygote develops, forms buds (asexually) which produce new medusa 30
  31. 31.  Box “jellyfish” Note prominent “eyes” Medusa dom body form  Polyp form unknown Strong swimmers, good hunters Toxic venom 31
  32. 32. Pedalium: flatblade at base ofeach tentacle →(see arrow) 32
  33. 33.  Sea anemones & coral found in this class; another is sea pens Medusa body form not seen All are marine, shallow water dwellers 33
  34. 34.  Polyps large, heavy  Attach to substrate via pedal discs, may burrow in sand/mud/silt  Tentacles ring the oral opening; mouth/anus slit shaped Reproduction: Sexual or asexual  Monoecious & dioecious individuals  Gonads internal; fertilization external  Zygote becomes a ciliated larva  Budding, pedal laceration, & fission may produce new individual asexually 34
  35. 35. Bonaire GiantAnemone ↓ Note fluorescence 35
  36. 36. Commensal relationships between fish & anemone Clown fish ↓Pink Anemone Fish ↑ Saddleback Clownfish 36
  37. 37. Brain Coral Two types of corals:  Zoantharian corals – true or stony corals  Octocorallian corals – soft corals, colonial Both form coral reefs  structures produced by living organisms. In most reefs the predominant organisms are colonial cnidarians that secrete an exoskeleton of calcium carbonate. The accumulation of this skeletal material, broken and piled up by wave action and bioeroders, produces massive calcareous formations that make ideal habitats for living corals and a great variety of other animal and plant life. 37
  38. 38.  Coral reefs are estimated to cover 284,300 km2, with the Indo-Pacific region (including the Red Sea, Indian Ocean, Southeast Asia and the Pacific) accounting for 91.9% of the total. Southeast Asia accounts for 32.3% of that figure, while the Pacific including Australia accounts for 40.8%. Atlantic and Carribean coral reefs only account for 7.6% of the world total. 38
  39. 39.  The Great Barrier Reef - largest coral reef system in the world, Queensland, Australia; The Belize Barrier Reef - second largest in the world, stretching from southern Quintana Roo, Mexico and all along the coast of Belize down to the Bay Islands of Honduras. The New Caledonia Barrier Reef - second longest double barrier reef in the world, with a length of about 1500km. The Andros, Bahamas Barrier Reef - third largest in the world, following along the east coast of Andros Island, Bahamas between Andros and Nassau. The Red Sea Coral Reef - located off the coast of Israel, Egypt and Saudi Arabia. Pulley Ridge - deepest photosynthetic coral reef, Florida 39
  40. 40.  The coral polyps do not photosynthesize, but have a symbiotic relationship with single-celled algae called zooanthellae these algal cells within the tissues of the coral polyps carry out photosynthesis and produce excess organic nutrients that are then used by the coral polyps. Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight. Indeed, the relationship is responsible for coral reefs in the sense that without their symbionts, coral growth would be too slow for the corals to form impressive reef structures. Corals can get up to 90% of their nutrients from their zooxanthellae symbionts. 40
  41. 41. Elkhorn CoralStar Coral Fluorescent Coral 41
  42. 42.  Coral reefs support an extraordinary biodiversity; although they are located in nutrient-poor tropical waters.  The process of nutrient cycling between corals, zooanthellae, and other reef organisms provides an explanation for why coral reefs flourish in these waters: recycling ensures that fewer nutrients are needed overall to support the community. Cyanobacteria also provide soluble nitrates for the coral reef through the process of nitrogen oxigen. Corals absorb nutrients, including inorganic nitrogen and phosporus, directly from the water, and they feed upon zooplankton that are carried past the polyps by water motion. 42
  43. 43.  Thus, primary productivity on a coral reef is very high, which results in the highest biomass per square meter, at 5-10g C m-2 day-1. Producers in coral reef communities include the symbiotic zooxanthellae, sponges, marine worms, seaweed, coralline algae(especially small types called turf algae. 43
  44. 44. Red Stalk JellyfishPortuguese Man-o-War This scyphozoan is unusual; it is attached not free floating 44
  45. 45. Note: Large float in this speciesVelella &Man-o-warare onlyscyphozoanswith floats 45
  46. 46. Orange Sea Pen 46
  47. 47. Sea FanArctic Jellyfish 47
  48. 48. x Jellyfish washed ashore 48
  49. 49.  Marine, prefer warmer H2O About 100 species known  Size range: few mm to 1.5m Medusa contains 8 rows of fused cilia plates for locomotion Some bioluminescent Have 2 tentacles; only 1 species known to have nematocysts 49
  50. 50.  Comb plates extend from aboral to oral end  Fused cilia along plate which beat from aboral to oral ends  All plates beat in unison, moving food toward mouth Two tentacles; long & retractable  Surface bearing colloblasts which are sticky 50
  51. 51. No central nervous system  Statocysts present for balance  Sensory cells in epidermisIndividuals are monoecious  Fertilization external  Some brood eggs  Larva free swimming 51
  52. 52. 52
  53. 53. Benthic Ctenophoran ←“Tortugas Red”Comb Jelly 53