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Cnidarians “The guys with the stinging tentacles”.

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Presentation on theme: "Cnidarians “The guys with the stinging tentacles”."— Presentation transcript:

1 Cnidarians “The guys with the stinging tentacles”

2 All About Cnidarians

3 Evolution of multicellular animals with tissues that perform special functions Cnidarians: Stinging animals Mostly marine 10,000 known species 2 body forms: medusa and polyp

4 Anatomy A. Polymorphism- Cnidarians have more than one body form: 1. Polyp 2. Medusa

5 The life history of some cnidarians includes both polyp and medusa stages. Others spend their entire lives as either polyp or medusa

6 medusa Free floating form which is transported by water currents, mouth with surrounding tentacles are positioned downward

7 Medusa Umbrella shape Tentacles around mouth Motile, Free-swimming

8 polyp Sessile, attached form with mouth and tentacles positioned upward

9 Polyp Form Tube with tentacles around the mouth Sessile Coral polyp

10 Polyp (sea anemone)

11 Polyp (Hydra)

12 Cnidarians Cnidarians actually exhibit radial symmetry in which similar body parts can be grouped around a central axis. Here we also observe a large jump on the evolutionary scale: tissues that perform specific functions.

13 Animals with radial symmetry look the same from all sides and have no head, front, or back. They do, however, have an oral surface, where the mouth is, and an aboral surface on the opposite side See figure 7.6 page 119


15 Radial Symmetry Compass jellyfish Radial

16 tissues Two layers present Epidermis covers body surface (external) Gastrodermis lines internal body cavity and is specialized for digestion There is also a narrow, gelatinous middle layer, mesoglea,that usually doesn’t contain cells. Forms “bell” of medusae


18 Cnidocytes Stinging cells Nematocyst capsules located on tentacles These are used for protection and feeding

19 Cnidocytes-Stinging Cells Within the cnidocyte is the nematocyst (which is like a capsule) The capsule has the stinging structure which is a hollow thread (Filament) with barbs Most contain a toxin Very small, but discharged in large numbers Usually the sting is only strong enough to kill zooplankton or tiny fish But there are exceptions!


21 Discharged nematocysts,Discharged nematocysts, stinging cells used for defense and prey capture, have been the plague of more than fish. stinging cells used for defense and prey capture, have been the plague of more than fish. Stings from certain jellyfish have resulted in death in a matter of hours, especially for infants.Stings from certain jellyfish have resulted in death in a matter of hours, especially for infants.

22 Discharging nematocyst c_N1Zk c_N1Zk

23 Jellyfish stings Tp38DUjUnM Tp38DUjUnM 1:01 B8kiZB0 B8kiZB0


25 Digestive and nervous systems Digestive system is incomplete (sac-like with mouth only) Centrally located mouth surrounded by tentacles Tentacles capture and handle food Mouth opens into gut where food is digested

26 Nerve net throughout body coordinates movements Some jellyfish also have sensory cells and contractile cells

27 One Opening System Food enters through the mouth and is digested in the cells. Wastes are excreted through the mouth. WASTES, GAMETES OUT Sperm and eggs are released through the mouth. FOOD IN

28 Response No nervous system No brain Nerve net around mouth Nerves cover the body but do not tell the difference between body parts.

29 Respiration Via diffusion Body is two cell layers thick

30 Habitat Aquatic: Most are Marine A few are freshwater

31 Feeding 1. Carnivores (predators) 2. Process of feeding a. Tentacles sting prey with nematocysts b. Tentacles grab prey c. Prey pulled into mouth 3. Prey moved into gastro-vascular cavity (GVC)* 4. GVC makes enzymes, breaks down food, extra-cellular digestion 5. Undigested food moves back out of mouth Lion ’ s mane eats another jelly!

32 Process of feeding 3. Prey stuffed into gastro- vascular cavity (GVC)* 4. GVC makes enzymes, extra- cellular digestion 5. Undigested food back out mouth *incomplete digestive tract (no anus)

33 Locomotion A.Medusa- motile, free-swimming B.Polyps- sessile, attached to hard substrate Exceptions: 1. Hydra tumbles on tentacles 2. Sea anemones glide on pedal disc

34 Reproduction 1. Asexual budding 2. Sexual a. Medusae release sperm & eggs b. Larvae are free-swimming

35 Sexual reproduction Medusa is normally the sexual stage with epidermal gonads. Eggs and sperm released from medusa Zygote develops into swimming larva called a planula Planula settles on bottom to form colony Eventually, new medusa are formed

36 Planula

37 Life Cycle of a Typical Cnidarian Alternation of Generations One form is the polyp (a cylinder with the closed end attached to the substrate and the open end with the mouth and tentacles directed upward) The other form is the medusa, free- swimming, with the mouth underneath (like a jellyfish)

38 Life Cycle of a Typical Cnidarian Alternation of Generations Hermaphrodite sexual asexual


40 Cnidarian life cycle Lmnu0I Lmnu0I bJ8qYWg bJ8qYWg

41 Phylum Cnidaria The Classes of Cnidaria are: Anthozoa- Sea Anemones and Corals Hydrozoa- Hydra Scyphozoa- “true” jellyfish Cubozoa- “box-shaped” jellyfish Ctenophora- non stinging Cnidarians:  Comb Jellies (covering separately)

42 Class Anthozoa All marine “flower animal” Corals, anemones, sea fans/whips, sea pansy Colonial polyps that normally lack a medusa stage Sting organisms around them Can move by crawling along the substrate Corals secrete calcium carbonate “shells” Most coral species possess symbiotic algae within body tissues called zooxanthellae

43 Anthozoa- sea fan

44 Anthozoa- anemone

45 Sea anemone

46 Giant Sea Anemone

47 Anthozoa- coral

48 Sun Coral

49 Brain Coral



52 Anemone Video 4DwEkkr0 4DwEkkr0

53 Homework Research the relationship between clown fish and anemones eo/animals/invertebrates-animals/other- invertebrates/clownfish_amonganemon es/ eo/animals/invertebrates-animals/other- invertebrates/clownfish_amonganemon es/

54 Class Scyphozoa True jellyfish. All marine Free swimming large medusa forms with polyp only in reproductive life They move by rhythmic contractions of the bell, but cannot fight against prevailing water currents Many with powerful stings

55 Scyphozoa

56 National geographic jellyfish Dance of the jellyfish eo/animals/invertebrates-animals/other- invertebrates/dance-jellyfish-eorg/ eo/animals/invertebrates-animals/other- invertebrates/dance-jellyfish-eorg/ 1 minute

57 National geographic eo/animals/invertebrates-animals/other- invertebrates/jellyfish/ eo/animals/invertebrates-animals/other- invertebrates/jellyfish/

58 Super Jellies 5F9CcLc 5F9CcLc 3:31

59 Jellyfish video XiTZdjo XiTZdjo 3:43 TqJLZc TqJLZc 11:08

60 Homework The case of the killer Cnidarians page 122 Research most deadly jellyfish Irukandji Carukia barnesi

61 Killer Jellyfish Cl_54Qh8 Cl_54Qh8 O021DMk O021DMk YbJSvTk YbJSvTk

62 worksheet “Killer Cnidarians” (Hoyle)

63 Life cycle of Scyphozoa

64 Largest known jellyfish Lion’s Mane Jelly bell of a lion's mane jellyfish can be over 8 feet across tentacles can reach over 100 feet, and they have many of them - the lion's mane jellyfish has eight groups of tentacles, and there are 70-150 tentacles in each group

65 Lion’s Mane Jellyfish

66 Encountering a lion's mane jellyfish probably won't be lethal, but it won't be fun, either. A lion's mane jellyfish sting usually results in pain and redness in the area of the sting. The sticky tentacles of a lion's mane jellyfish can sting even when the jellyfish is dead, so give lion's mane jellyfish on the beach a wide berth. In 2010, a lion's mane jellyfish washed ashore in Rye, NH, where it stung 50-100 unsuspecting batherswashed ashore

67 Class Hydrozoa Mostly polyp forms with reproductive medusa Freshwater and marine Physalia Portuguese man of war hydra

68 Hydrozoa

69 Hydra Exist only as polyps

70 Portuguese man of war

71 National geographic portuguese man of war nimals/invertebrates/portuguese-man- of-war/ nimals/invertebrates/portuguese-man- of-war/

72 National geographic port. Man of war CpcapB0s CpcapB0s

73 Ecological Role A.Predators and prey B.Neurotoxins in medical research C.Coral – jewelry, building, reefs (surfing!) D.Coral reefs - habitat for many different species, great biodiversity, protect coastline E. Symbiosis with other organisms

74 Cnidarians Documentary WOeM3uA WOeM3uA 9:17

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