Chapter 8. Sponges, Cnidarians, Comb Jellies, and Marine Worms

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1 Chapter 8 Sponges, Cnidarians, Comb Jellies, and Marine Worms

2 Cnidarians: Animals with Stinging Cells Phylum Cnidaria Includes hydroids, corals, and sea anemones Coelenterate: synonym Named for their cnidocytes Stinging cells Used to capture prey & for protection

3 Organization of the Cnidarian Body Radial symmetry Many planes can be drawn through the central axis that will divide the animal into equivalent halves

4 Organization of the Cnidarian Body Often exhibit 2 body plans within their life cycles Polyp Benthic form characterized by a cylindrical body with mouth surrounded by ring of tentacles Medusa Free-floating stage (jellyfish)

5 Two body plans: polyp and medusa

6 Cnida Stinging Cells stinging organelle within a cnidocyte may function in locomotion, prey capture, or defense Nematocysts spearing type, which are discharged when the cnidocil a bristle-like trigger contacts another object

7 Structure of stinging cell and nematocyst.

8 Examples of Dangerous Species Portuguese man o war (painful stings) Colony of many specialized individuals Immediate pain and swelling Usually not fatal

9 Examples of Dangerous Species Box jellyfish Can kill within 3-20 minutes Leave scars

10 How to Treat a Jellyfish Sting

11 Types of Cnidarians Class Hydrozoa: Hydrozoans or Hydroids Mostly colonial organisms Members physically connected and adapted to share resources Colonial forms typically contain 2 types of polyp Feeding polyp (gastrozooid) functions in food capture & feeding colony Reproductive polyp (gonangium) specialized for reproduction

12 Drawing showing reproductive and feeding polyps of colonial hydrozoan Tubularia.

13 Types of Cnidarians Medusae are usually small Some float with current Medusae of Gonionemus crawls along bottom Hydrocorals (Millepora and Stylaster) secrete a calcareous skeleton and resemble hard corals

14 Types of Cnidarians Members of hydrozoan orders Siphonophora (Portuguese Man O War) and Chondrophora (bythe-wind sailor) produce floating colonies Example: Portuguese man o war Colony suspended from gas sac acting as float & developed from polyp Found in the Atlantic, Pacific, Indian, and Caribbean Oceans Specialized polyps: Bladder polyp Feeding polyp Digesting polyp Reproductive polyp

15 Class Scyphozoa Scyphozoans Medusa is dominant life stage Referred to as true jellyfish Swim horizontally & vertically by pulsating their bodies Float with current Moon jelly common in coastal waters Photoreceptors sense organs that can determine whether it is dark or light

16 Class Cubozoa Box Jellyfish Sea wasp Marine stinger Tropical voracious predators, primarily of fish multiple species: some more dangerous than others

17 Cubuzoans Venom is considered to be among the most deadly in the world Toxins attack the heart, nervous system, and skin cells.

18 Class Cubozoa Live primarily in coastal waters off Northern Australia and throughout the Indo-Pacific. Pale blue and transparent in color and get their name from the cube-like shape of their bell. Some grow tentacles that can reach 10 feet (3 meters) in length.

19 Box Jellyfish Stings and Fatalities

20 Class Anthozoa Anthozoans Sea anemones, corals, gorgonians (sea whip or sea fan), & their relatives Benthic Sessile adults

21 Sea anemones: polyps with a vascular cavity divided into multiple compartments radiating from the central one capable of expanding, contracting, & reaching with tentacles to capture prey though sessile, many can change locations

22 Coral animals Anthozoans Polyps that secrete a hard or soft skeleton

23 Anthozoans Hard or stony corals Produce skeleton of calcium carbonate Form large colonies of small polyps - reefs Live symbiotically with algae & receive nutrients from algae

24 Coral polyps from Caribbean with tentacles extended for feeding Thomson-Brooks Cole

25 Mushroom coral: solitary polyp (25 cm diameter) similar in structure to sea anemone

26 Anthozoans Soft corals Examples: sea fans & sea pens Have 8 feathery tentacles Polyps that form plantlike colonies

27 Sea pansy: Common along coast Flattened horizontal surface reduces resistance to turbulent water 2006 Thomson-Brooks Cole

28 Nutrition and Digestion Gastrovascular cavity central cavity where cnidarians digest their prey Functions in digestion and transport of materials Waste material forced back out through mouth Many hydrozoans and anthozoans are filter feeders (feed on plankton)

29 Nutrition and Digestion Jellyfish and box jellyfish are carnivorous Eat fish and invertebrates Prey paralyzed by toxin from nematocyst & possibly entangled by fibers

30 Nutrition and Digestion Sea anemones (Anthozoan) generally feed on invertebrates Larger species can feed on fish Nutrition from symbiotic algae for shallow water species

31 Circulatory System Cnidarians do not need an advanced circulatory system because most cells come within direct contact with the surrounding water.

32 Reproduction Cnidarians can reproduce sexually & asexually Asexual reproduction usually occurs in polyp stage Anthozoans reproduce sexually and asexually in polyp stage Sexual reproduction usually occurs in medusa stage

33 Life Cycle of the Hydrozoan: Sexual stage of life cycle is medusa Fertilized egg develop into planula larva that will settle & grow into polyp Polyp reproduces asexually through budding Ephyra = juvenile form of medusa

34 Life Cycle of Scyphozoan: Adult medusae sexes are separate Medusae sexual stage in life cycle gametes released in water column Fertilized egg develops into planula larvae which becomes polyp Polyps reproduce medusa buds asexually 2006 Thomson-Brooks Cole

35 Reproduction Anthozoans (for example sea anemone) Asexual reproduction Pedal laceration leaving parts of the pedal disk (anemone base) behind to grow into new animals Fission the anemone splits in two and each half grows into a new individual Budding produces large colonies of identical hard corals

36 Reproduction Anthozoans (for ex: sea anemone) Sexual reproduction Sexes can be separate Some anemones are hermaphroditic Produce one type of gamete each reproductive period Fertilization in gastrovascular cavity or water column Larval stage is a planula larva Eventually settles on solid surface to form adult

37 Ecological Relationships of Cnidarians Predator-prey relationships Cnidarians are predators Stinging cells discourage predation (fed on by sea turtles, some fish, and molluscs) Habitat formation Coral polyps form complex 3-dimensional structures inhabited by thousands of other organisms Coral reefs provide a solid surface for attachment, and buffer waves and storms

38 Ecological Relationships of Cnidarians Symbiotic relationships Portuguese manof-war and manof-war fish Fish swims unharmed in tentacles of manof-war & serves as lure for other fish

39 Ecological Relationships of Cnidarians Reef-forming corals and zooxanthellae Algae provide food for corals and other reef animals

40 Ecological Relationships of Cnidarians Symbionts of sea anemones Clownfish act as lure & feed on scraps of prey Hermit crab anemone attach to shell; crab is camouflaged; anemone gets food & transportation

41 Ctenophores Phylum Ctenophora Comb jellies Planktonic, nearly transparent Ctenophore structure Named for 8 rows of comb plates which the animal uses for locomotion Composed of large cilia Lack stinging cells Exhibit radial symmetry Bioluminescent

42 Ctenophores Digestion and nutrition Carnivorous Feed on other planktonic animals May use branched tentacles in a net pattern, adhesive cells, or stolen jellyfish stingers 2006 Thomson-Brooks Cole

43 Ctenophores Reproduction almost all are hermaphroditic fertilization may be in the water column, or eggs may be brooded in the body free-swimming larva resembling the adult ctenophore