13-1 CHAPTER 13 Phylum Cnidaria

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phylum Cnidaria Fossil specimens dated to over 700 million years ago General Characteristics Soft bodied Carnivorous Stinging tentacles Examples: Jellyfish, sea anemones

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Classes of Cnidaria Classes of Cnidaria Hydrozoa (Portuguese Man-of-War, Hydra) Hydrozoa (Portuguese Man-of-War, Hydra) Scyphozoa (True Jellyfish - Aurelia) Scyphozoa (True Jellyfish - Aurelia) Anthozoa (Sea Anenome, Corals) Anthozoa (Sea Anenome, Corals) Cubazoa (Box Jellies-- Poison) Cubazoa (Box Jellies-- Poison)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Characteristics of Phylum Cnidaria All are aquatic and mostly marine All are aquatic and mostly marine Symmetry Symmetry Radial Radial Two body types Two body types Free-swimming medusa Free-swimming medusa Sessile polyps Sessile polyps Acoelomates - No coelom Acoelomates - No coelom Diploblastic Diploblastic Blind (Incomplete) Gut Blind (Incomplete) Gut

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Form and Function Cnidaria have two basic body plans: polyp and medusa Cnidaria have two basic body plans: polyp and medusa Polyp Polyp Adaptation to a sedentary life Adaptation to a sedentary life Tubular body with the mouth directed upward and surrounded by tentacles Tubular body with the mouth directed upward and surrounded by tentacles Mouth leads into a blind-gut cavity Mouth leads into a blind-gut cavity Reproduce asexually by budding, fission, or pedal laceration Reproduce asexually by budding, fission, or pedal laceration

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria - Medusa Medusa Medusa Bell or umbrella-shaped Bell or umbrella-shaped Usually free-swimming Usually free-swimming Mouth directed downward Mouth directed downward Tentacles may extend down from rim of umbrella Tentacles may extend down from rim of umbrella

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Tentacles usually encircle mouth or oral region Tentacles usually encircle mouth or oral region Equipped with specialized cells: cnidocytes Equipped with specialized cells: cnidocytes Cnidocytes: stinging cells located on their tentacles Cnidocytes: stinging cells located on their tentacles Nematocyst: stinging organelle, poison-filled structure that contains a tightly coiled dart. Nematocyst: stinging organelle, poison-filled structure that contains a tightly coiled dart. Tactile stimulation of cnidocil, causes nematocyst to discharge Tactile stimulation of cnidocil, causes nematocyst to discharge After discharge, cnidocyte is absorbed and another develops After discharge, cnidocyte is absorbed and another develops Mechanism of Nematocyst Discharge Mechanism of Nematocyst Discharge When stimulated, water rushes into the capsule When stimulated, water rushes into the capsule The operculum (cap) opens and rapidly launches the filament The operculum (cap) opens and rapidly launches the filament Barbs inject poison into prey Barbs inject poison into prey Box Jellyfish - and the Portuguese man-of-war can seriously harm humans Box Jellyfish - and the Portuguese man-of-war can seriously harm humans

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cnidarian Phyla Topical Solutions if stung: Topical Solutions if stung: acidic (vinegar) acidic (vinegar) Urine - only if urine is acidic?? Most urine is sterile. Urine - only if urine is acidic?? Most urine is sterile. Apply heat or ice for pain (also denatures toxins) Apply heat or ice for pain (also denatures toxins) Salt water should be applied to remove any excess toxins. Salt water should be applied to remove any excess toxins.

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria OTHER CNIDARIAN CHARACTERISTICS Sense organs for balance (statocysts) and photosensitivity (ocelli) Sense organs for balance (statocysts) and photosensitivity (ocelli) Nerve net Nerve net Simple nervous system, no brain Simple nervous system, no brain Asexual reproduction Asexual reproduction Budding in polyps Budding in polyps Sexual reproduction Sexual reproduction By gametes in all medusa and some polyps By gametes in all medusa and some polyps Monoecious or Dioecious Monoecious or Dioecious No excretory or respiratory system No excretory or respiratory system

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Life Cycles Typically, zygote develops into a motile planula larva Typically, zygote develops into a motile planula larva Planula settles, and metamorphoses into a polyp Planula settles, and metamorphoses into a polyp Produce other polyps asexually Produce other polyps asexually Polyps eventually produce a free-swimming medusa by asexual reproduction (Budding) Polyps eventually produce a free-swimming medusa by asexual reproduction (Budding) Phylum Cnidaria Hydrazoan Life Cycle

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Body Wall Cnidarian body Cnidarian body Outer epidermis Outer epidermis Inner gastrodermis (gastrovascular cavity = gut) Inner gastrodermis (gastrovascular cavity = gut) Layers separated by mesoglea Layers separated by mesoglea Mesoglea Mesoglea Gelatinous (at least 95% water) - jellylike Gelatinous (at least 95% water) - jellylike Continuous, extending through body and tentacles Continuous, extending through body and tentacles Supports body Supports body Thickness varies Thickness varies

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Class Hydrozoa Most marine and colonial with both polyp and medusa forms (polyp form dominates) Most marine and colonial with both polyp and medusa forms (polyp form dominates) Colonial Obelia Colonial Obelia Typical hydroid has a base, a stalk, and one or more individual polyp animals Typical hydroid has a base, a stalk, and one or more individual polyp animals Feeding polyps with tentacles around mouth= hydranths Feeding polyps with tentacles around mouth= hydranths In Obelia, the medusa buds are formed by a reproductive polyp called a gonangium In Obelia, the medusa buds are formed by a reproductive polyp called a gonangium

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Class Hydrozoa: Animals Class Hydrozoa: Animals Hydra Hydra Found in fresh water Found in fresh water Worldwide distribution (16 species in North America) Worldwide distribution (16 species in North America) Polyp body form Polyp body form Ring of 6–10 hollow tentacles encircles mouth Ring of 6–10 hollow tentacles encircles mouth Portuguese Man-of-War Portuguese Man-of-War Floats on surface (air bladder) Floats on surface (air bladder) Tentacles reach up to 10 meters Tentacles reach up to 10 meters Contains polyp colonies and medusa Contains polyp colonies and medusa Air bladder contains gases released Air bladder contains gases released

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Differences between Hydrozoa and Scyphozoa Hydrozoa Colonial Stages Mostly Polyp life form Medusa, if present, are usually small Small amounts of mesoglea Less tentacles Scyphozoa Large Medusa forms Cells present in mesoglea More complex More tentacles Large amount of mesoglea

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Class Scyphozoa Most of the larger jellyfishes belong to this class Most of the larger jellyfishes belong to this class Nearly all float in open sea Nearly all float in open sea Bells vary in shape and size Bells vary in shape and size Composed mostly of mesoglea Composed mostly of mesoglea

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria - Scyphozoa Phylum Cnidaria - Scyphozoa Reproduction methods Reproduction methods Asexual - Similar to other cnidarians. Budding Asexual - Similar to other cnidarians. Budding But also use Strobilation - asexual budding of saucerlike buds that develop into medusa. But also use Strobilation - asexual budding of saucerlike buds that develop into medusa.

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Class Anthozoa Lack a medusa stage Lack a medusa stage All marine, in both deep and shallow water, and vary in size All marine, in both deep and shallow water, and vary in size Examples: sea anemones, sea corals Examples: sea anemones, sea corals

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria - Anthozoa Sea Anemones Polyps larger and heavier than hydrozoan polyps Polyps larger and heavier than hydrozoan polyps Attach to shells, rocks, timber, etc. by pedal discs Attach to shells, rocks, timber, etc. by pedal discs Crown of tentacles surrounds the flat oral disc Crown of tentacles surrounds the flat oral disc When in danger, water rapidly expelled through pores as the anemone contracts to a small size When in danger, water rapidly expelled through pores as the anemone contracts to a small size

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria - Anthozoa Reproduction of Sea Anemones Reproduction of Sea Anemones Some dioecious, some monoecious Some dioecious, some monoecious Monoecious species - produce sperm first and eggs later Monoecious species - produce sperm first and eggs later Fertilization is external or in gastrovascular cavity Fertilization is external or in gastrovascular cavity Zygote becomes a ciliated larva Zygote becomes a ciliated larva Pedal laceration, small pieces of pedal disc break off and regenerate a small anemone Pedal laceration, small pieces of pedal disc break off and regenerate a small anemone Budding can occur Budding can occur

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria Coral Reefs Coral Reefs Great diversity of organisms (under rainforest) Great diversity of organisms (under rainforest) Plants and animals are limited to top layer Plants and animals are limited to top layer Above the calcium carbonate deposits Above the calcium carbonate deposits Reef forming corals and algae precipitate calcium carbonate to form most coral reefs Reef forming corals and algae precipitate calcium carbonate to form most coral reefs Require warmth, light, and salinity of undiluted sea water (contains calcium) Require warmth, light, and salinity of undiluted sea water (contains calcium) Photosynthetic zooxanthellae live in their tissues Photosynthetic zooxanthellae live in their tissues Provide food for corals, carbon for calcium carbonate, and recycle phosphorus and nitrogenous wastes Provide food for corals, carbon for calcium carbonate, and recycle phosphorus and nitrogenous wastes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phylum Cnidaria - Human Impact Nutrients from fertilizer and sewage threaten coral reefs with excessive algal growth - or by killing zooxanthellae, which leads to coral bleaching. Nutrients from fertilizer and sewage threaten coral reefs with excessive algal growth - or by killing zooxanthellae, which leads to coral bleaching. Persian Gulf reefs have withstood surprising amounts of oil pollution Persian Gulf reefs have withstood surprising amounts of oil pollution Coral reefs in many areas are threatened by factors mostly of human origin Coral reefs in many areas are threatened by factors mostly of human origin HUMAN IMPACT: