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Presentation on theme: "PHYLUM: CNIDARIA."— Presentation transcript:


2 Classes of Cnidaria Class Hydrozoa (e.g., Hydra, Obelia)
Class Scyphozoa (e.g., Aurelia) Class Cubozoa (e.g., cube jellies) Class Anthozoa (anemones and corals) Subclass Hexacorallia (sea anemones, hard corals) Subclass Octocarallia (sof corals)

3 General Characteristics
Entirely aquatic; mostly marine, but with a few freshwater species; may be solitary or colonial Metazoan, with true tissues. Diploblastic – two germ layers outer cell layer known as ectoderm (epidermis), inner cell layer known as endoderm (=gastrodermis), with a non-cellular mesoglea between.

4 General Characteristics
The internal body space (gastrovascular cavity) lined with gastrodermis has a mouth, but no anus (incomplete digestive tract) Possess cnidocytes with special cell organelles - nematocysts, used for defense and offense

5 General Characteristics cont.
Phylum exhibits polymorphism Metagenesis- alternation of generation Polyp (often sessile) and the medusa (free swimming). The polyp stage reproduce asexually, while the medusa stage usually reproduces sexually Reproduction is asexual by budding and/or sexual, producing a ciliated planula larva

6 Figure 13.02 Two general body forms


8 Class Hydrozoa solitary or colonial
alternation of asexual polyps and sexual medusae

9 Figure 13.09



12 Hydra with Bud Ovary Bud

13 Hydra with Gonads Testes

14 Gastrovascular cavity Hydra c.s. Epidermis Mesoglea Gastrodermis

15 Figure 13.09 Obelia Life Cycle

16 Obelia - Medusa Gonad Tentacle Gastrovascular cavity

17 Obelia – Hydroid colony
Gastrozoids = Hydranth Gonozoids = Gonangium

18 Obelia – Hydroid Colony
Gonozooid Hydrozooid

19 Gonionemus Gonad

20 Physalia – Portuguese Man-O-War - a colony, not an individual
It is not a jellyfish!!

21 Class Scyphozoa True Jellyfishes
polyp stage reduced or absent bell-shaped medusae margin of bell with eight notches which are provided with sense organs all marine


23 Aurelia - Medusa

24 Aurelia - Planula larva

25 Aurelia - Scyphistoma

26 Aurelia - Strobila

27 Aurelia - Ephyra

28 Class – Anthozoa Sea Anemones and Corals
all species occur as polyps only, no medusae; gastrovascular cavity partitioned by at least eight septa with nematocysts Solitary or colonial all marine.



31 Some Hydrozoans

32 Figure 13.07

33 0022.jpg 0022.jpg


35 Figure 13.15a

36 Figure 13.15b

37 Some Scyphozoans

38 Jellyfishes

39 Figure 13.16

40 Figure 13.17

41 Some Anthozoans

42 Sea Anemones

43 Figure 13.25


45 Figure 13.29


47 Corals

48 Figure 13.32

49 Figure 13.33a

50 Figure 13.33b

51 Figure 13.28

52 0039.jpg 0039.jpg

53 0041.jpg 0041.jpg

54 0047.jpg 0047.jpg

55 0048.jpg 0048.jpg

56 Figure 13.26b

57 Figure 13.26c

58 0049.jpg 0049.jpg

59 0050.jpg 0050.jpg

60 Phylum Ctenophora The Combjellies

61 General Characteristics
Biradial symmetry Eight rows of comb plates Tentacles possess colloblasts Triploblastic (three cell or germ layers) Mesoglea (loose mesenchyme) is jelly-like material strews with fibers and amebocytes and contains true muscle cells Aboral sense organ (statocyst) Digestive system: mouth, pharynx, stomach, branched canals and anal pore Monoecious, with both eggs and sperm produced from endodermal lining of digestive canals beneath comb plates

62 Figure 13.36

63 Figure 13.36a

64 Figure 13.38

65 Figure 13.38a

66 Figure 13.38b

67 Figure 13.35

68 0002.jpg 0002.jpg

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