1. Phyla Cnidaria and Ctenophora

2. Domain Eukarya
Kingdom Animalia

3. Phyla Cnidaria
Marine members include jellyfishes, sea anemones, corals, and hydroids.

4. Cnidaria and Ctenophora exhibit radial symmetry
Body Plan
Cnidaria and Ctenophora exhibit radial symmetry

7. Relatively simple, diffuse nerve net
Nervous System
Relatively simple, diffuse nerve net
lacks a central brain to process sensory info. or to organize complex responses

10. Different degrees of centralization in metazoan brains.
Different degrees of centralization in metazoan brains. (a) Centralized nervous system of an oligochaete worm. (b) Nerve net of a cnidarian polyp representing a typical non-centralized nervous system. Schematized drawings modified with permission from Bullock & Horridge (1965).
Arendt D et al. Phil. Trans. R. Soc. B 2008;363:
©2008 by The Royal Society

11. Mouth is located at the center of the body on the oral side.
The opposite side is the aboral side

14. Box Jellyfish
Box Jellyfish                           

15. Uncharacteristically advanced Cnidarian
Uncharacteristically advanced Cnidarian. Primitive eyes (eyespots) are present. When they detect a dark spot, they go the other way.

18. Structure and Function
The body may be either vase- shaped (polyp) or bell-shaped (medusa)

19. Polyp is sessile and benthic.
Tentacles and mouth face upward

21. Medusa is free-swimming
Tentacles and mouth face downward

23. All cnidarians have bodies constructed of two layers
Epidermis is outer layer
Gastrodermis is inner layer

24. A. gastrovascular cavity
B. gastrodermis
C. mesoglea
D. nematocysts
E. epidermis (integument)

25. Diploblasty is a condition of the blastula in which there are two primary germ layers: the ectoderm and endoderm.

26. Between the layers is a jellylike mesoglea
A centrally located mouth leads to a baglike digestive tract- the gastrovascular cavity

28. Cnidarian feeding and Defense
Tentacles that surround the mouth are covered with specialized cells- cnidocytes

30. Cnidocytes produce organelles called nematocysts

31. Nematocysts are stinging organelles that exit the cnidocyte (cnidoblast) with great force once triggered

33. The nematocyst capsule stores a large concentration of calcium ions, which are released from the capsule into the cytoplasm of the cnidocyte when the trigger is activated. This causes a large concentration gradient of calcium across the cnidocyte plasma membrane. The resulting osmotic pressure causes a rapid influx of water into the cell. This increase in water volume in the cytoplasm forces the coiled nematocyst to eject rapidly.

35. Some nematocysts are adhesive, others have filaments to entangle prey, and others have spines that puncture prey.

37. Tentacles capture prey
Cnidocytes release nematocysts into prey, paralizing it.
Tentacles push prey into mouth

38. 4. Enzymes in gastrovascular cavity break up prey 5
4.Enzymes in gastrovascular cavity break up prey 5.Gastrodermis cells absorb nutrients 6.Waste exits mouth

39. Classification of Cnidaria
Four classes
Hydrozoa
Scyphozoa
Cubozoa
Anthozoa

40. Class Hydrozoa
3700 species
Most live as colonial organisms

41. Obelia Many polyps attached to branched stalks
Some polyps function in gathering food; others are responsible for reproduction

42. Oblia

46. Order siphonophores Physalia physalis
Portuguese man-of-war
Exists as a colony of medusea and polyps

47. Pneumatophore- a single individual polyp (gas- filled float)
Dactylozooids- (tentacles) polyps specialized for capturing prey

49. Gastrozooids- polyps specialized for digestion
Gonozooids- polyps specialized for reproduction

51. Class Scyphozoa “Cup Animals” Medusa is dominant form of life cycle
Commonly known as jellyfish

52. largest (Cyanea capillata, or lion’s mane), which has a bell that measures 6 feet across

53. Pulsating motion of the cup propels the jellyfish
Common jellyfish have life cycle that includes both medusa and polyp

54. Common jellyfish reproduction

55. 1. Adult Male and Female

56. 2. Egg and Sperm are Released

57. Fertilization

58. Blastula Formation

59. Planula Development

60. Benthic Attachment

61. Polyp Develops

62. Stacks of Medusae form and detach

63. Young Medusa is Released

65. Class Cubozoa
Box Jellies
Most advanced and deadly
eyespot

66. (Irukandji, Carukia barnesi) which is the size of your fingernail.

67. Class Anthozoa “Flower Animals” ~6100 Species
Examples include Sea anemones and corals

69. Sea anemones are benthic polyps
Commonly found in coastal areas
Feed on fishes and other small animals

70. Symbiotic relationship with clownfish.
Corals are small polyps that usually live in colonies.

71. Each polyp cements its calcium carbonate skeleton to the skeletons of others
Live symbiotically with algae

75. Phylum Ctenophora “Comb holder”- comb jellies ~100 species
Move by beating cilia (ctenes) lined along body

76. Secrete sticky substance from colloblasts.
Some have cnidocytes they recycle from eating cnidarians

77. Two tentacles
Bioluminescent