Phylum Cnidaria

1. Phylum Cnidaria

2. Hydras, jellyfish, sea anemones, and corals belong to the phylum Cnidaria. • these diverse animals are all armed with stinging cells called nematocysts • The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle. Casually touching many cnidarians will make it clear how they got their name when their nematocysts eject barbed threads tipped with poison.

3. Cnidarians have two basic body forms, and both show radial symmetry. • Medusa forms are free-floating, jellylike, and often umbrella-shaped. • Polyp forms are tube like and are usually attached to a rock or some other object. • Polymorphic- alternates between polyp and medusa

5. General Characteristics • 1. Radial symmetry is primary • 2. Gastrovascular cavity for digestion • 3. Tentacles - feeding, locomotion, defense

6. Reproduction in polyps is by asexual budding (polyps) or sexual formation of gametes (medusae, some polyps). Cnidarian individuals may be monoecious or dioecious. The result of sexual reproduction is a planula larva, which is ciliated and free-swimming. • Embryo --> planula --> polyp or medusa

8. Classes • Class hydrozoa- hydra, fire coral, Portuguese man-of-war • Class scyphozoa- jelly fish • Class cubozoa- box jellies • Class Anthozoa-anemones, corals

9. Hydrozoa • 2700 species of hydras, colonial hydroids, fire corals • polyp, medusa, polymorphic

10. Hydra

11. Freshwater Hydrozoa • Hydras live in quiet ponds, lakes, and streams. • They attach to rocks or water plants by means of a sticky secretion they produce in an area of their body called the basal disk

12. Marine hydrozoans are typically far more complex than freshwater hydrozoans. • Often many individuals live together, forming colonies

13. Most hydrozoans are colonial organisms whose polyps reproduce asexually by forming small buds on the body wall. Many hydrozoans are also capable of sexual reproduction. • During sexual reproduction, the medusas release sperm or eggs into the water. • The gametes fuse and produce zygotes that develop into free-swimming, ciliated larvae called planulae.

16. Feeding • Hydra mainly feed on small aquatic invertebrates such as Daphnia and Cyclops (water flea). • When feeding, Hydra extend their body to maximum length and then slowly extend their tentacles. Despite their simple construction, the tentacles of Hydra are extraordinarily extensible and can be four to five times the length of the body

18. Tissue Differentiation and Body Wall a. Epidermis • interstitial cells - capable of forming other tissues • nerve cells - sensory and motor • cnidocytes - discharge nematocysts, used once b. Mesoglea • jelly-like matrix, mostly acellular, fluid or rigid c. Gastrodermis • nutritive-muscle and enzymatic cells

19. Hydra dance video • Hydra eating video

20. Portuguese Man-of-war

21. Despite its outward appearance, the man o' war is not a jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single organism, but a colonial organism made up of many minute individuals called zooids. • they are attached to one another and physiologically integrated to the extent that they are incapable of independent survival

22. The Portuguese man o' war lives at the surface of the ocean. The gas-filled bladder, or pneumatophore, remains at the surface, while the remainder is submerged.Since the man o' war has no means of propulsion, it is moved by a combination of winds, currents, and tides

24. It is composed of four types of polyp. One of the polyps, a gas-filled bladder called the pneumatophore (commonly known as the sail), enables the organism to float. This sail is bilaterally symmetrical, with the tentacles at one end, and is translucent, tinged blue, purple, pink, or mauve. It may be 9 to 30 centimetres (3.5 to 12 in) long and may extend as much as 15 centimetres (5.9 in) above the water.

26. The other three polyp types are known as dactylozooid (defence), gonozooid (reproduction), and gastrozooid (feeding).These polyps are clustered. The dactylzooids make up the tentacles that are typically 10 metres (33 ft) in length but can be up to 50 metres (160 ft

27. Diet • The Portuguese man o' war is a carnivore. Using its venomous tentacles, a man o' war traps and paralyzes its prey. Typically, men o' war feed upon small aquatic organisms, such as fish and plankton.

28. The predators • The loggerhead turtle feeds on the Portuguese man o' war, a common part of the loggerhead's diet.The turtle's skin is too thick for the sting to penetrate. • The sea slug Glaucusatlanticus also feeds on the Portuguese man o' war,as does the violet snail Janthinajanthina. • The blanket octopus is immune to the venom of the Portuguese man o' war; young individuals carry broken man o' war tentacles, presumably for offensive and/or defensive purposes

31. Fire Coral

32. Fire corals are colonial marine organisms that look rather like real coral. • Fire corals have a bright yellow-green and brown skeletal covering and are widely distributed in tropical and subtropical waters. They appear in small brush-like growths on rocks and coral.

33. Divers often mistake fire coral for seaweed, and accidental contact is common. Upon contact, an intense pain can be felt that can last from two days to two weeks

35. Fire coral has several common growth forms, these include: • branching • Plate • encrusting

36. Branching adopts a calcareous structure which branches off, to rounded finger-like tips Branching

37. Plate adopts a shape similar to that of the smaller non-sheet lettuce corals; therefore erect, thin sheets, which group together to form a colony Plate

38. Encrusting encrusting, is where the fire coral forms on the calcareous structure of other coral

39. Structure • The polyps of fire corals are near microscopic size and are mostly embedded in the skeleton and connected by a network of minute canals. All that is visible on the smooth surface are pores of two sizes: gastropores and dactylopores

40. Dactylopores have long fine hairs that protrude from the skeleton. The hairs possess clusters of stinging cells and capture prey, which is then engulfed by gastrozooids, or feeding polyps, situated within the gastropores

41. Reproduction • Reproduction in fire corals is more complex than in other reef-building corals. The polyps reproduce asexually, producing jellyfish-like medusae, which are released into the water from special cup-like structures known as ampullae.

42. The medusae contain the reproductive organs that release eggs and sperm into the water. Fertilized eggs develop into free-swimming larvae that will eventually settle on the substrate and form new colonies. Fire corals can also reproduce asexually by fragmentation

43. Class Scyphozoa

44. Jelly fish • Medusa form • They are classified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles

46. Most jellyfish do not have specialized digestive, central nervous, respiratory, or circulatory systems. • The manubrium is a stalk-like structure hanging down from the center of the underside, with the mouth at its tip.

47. The manubrim opens into the gastrovascular cavity, where digestion takes place and nutrients are absorbed. • It is joined to the radial canals which extend to the margin of the bell. • Jellyfish do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion.

48. They have limited control over movement, but can use their hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are mostly passive.

49. Depending on the species, the body contains between 95 and 98% water. • Most of the umbrella mass is a gelatinous material (the jelly)called mesoglea which is surrounded by two layers of protective skin. • The top layer is called the epidermis, and the inner layer is referred to as gastrodermis, which lines the gut.