Who, What, When, Where, Why, and How of Lower Invertebrates

1. Who, What, When, Where, Why, and How ofLower Invertebrates • Who studies invertebrates? • What are invertebrates? • When did bilateral symmetry evolve? • Where are invertebrates found? • Why are invertebrates important to the Marine Ecosystem? • How do marine invertebrates influence the marine ecosystem?

2. Chapter 8 Lower Invertebrates

3. What Are Animals? • Animals: • are multicellular • distinguishes them from bacteria and most protists • have eukaryotic cells without cell walls • distinguishes them from bacteria, fungi, algae and plants • cannot produce their own food, depend on other organisms for nutrients • can actively move at least at some point during their life cycle • invertebrates = animals that lack a vertebral column (backbone • vertebrates – animals with a vertebral column • majority of animals in sea are invertebrates

4. The first animals we will talk about are sponges • They are assymetrical – no symmetry • No true tisses

5. Phylum Porifera: Sponges • Basic characteristics: • simple • asymmetric • sessile: permanently attached to a solid surface • have many shapes, sizes and colors • shape often determined by shape of bottom sediments, material on which they are growing and local water currents

6. Sponge Structure and Function • Body is built around a system of water canals • ostia: tiny holes or pores through which water enters the sponge’s body • spongocoel: spacious cavity in the sponge into which water flows • osculum: large opening through which water exits from the spongocoel

7. Water exits through osculum Spicule Archaeocyte Pinacocyte Water enters through small pores (ostia) Spongocoel Pore cells Spongocoel Collar cell (choanocyte) Collar Flagellum Ostium Food particles Stepped Art Fig. 8-1, p. 193

8. Sponge Structure and Function • Lacking tissues, sponges have specialized cells • collar cells (choanocytes) use their flagella to provide force for moving water through the sponge’s body • pinacocytes in a layer provide an outer covering for the sponge • archaeocytes: cells that resemble amoebas, and can move through sponge body • can assume any of the other cell forms • transport materials • important role in repair and regeneration

9. Sponge Structure and Function • Structural materials • spicules: skeletal elements that give support to a sponge’s body, produced by specialized cells and composed of calcium carbonate, silica or sponging • Helps also with protection – will keep other animals from eating the sponges

10. Sponge Structure and Function • Nutrition and digestion • sponges are suspension feeders – feed on material suspended in seawater • sponges are also referred to as filter feeders – they filter food from the water

11. Ecological Roles of Sponges • Competition • compete aggressively with corals and bryozoans for attachment space • Predator-prey relationships • few species eat sponges • spicules are like needles • some produce chemical deterrents • a few species of bony fish and molluscs and sea turtles (especially the hawksbill) will eat sponges

13. Ecological Roles of Sponges • Symbiotic relationships • sponges are mutualistic or commensalistic hosts to many organisms • e.g. symbiotic cyanobacteria • many organisms (shrimp, fish) live within the canals or spongocoel, for protection and to take advantage of water flow

14. Now we will talk about animals with radial symmetry

15. Phylum Cnidaria • Animals with stinging cells • Include jellyfish, hydroids, corals and sea anemones • Named for their cnidocytes—stinging cells • Cnidocytes are used to capture prey and protect the animal

16. Organization of the Cnidarian Body • Radial symmetry: many planes can be drawn through the central axis that will divide the animal into equivalent halves • Often exhibit 2 body plans within their life cycles: • polyp: benthic form characterized by a cylindrical body with an opening at 1 end, i.e., the mouth which is surrounded by tentacles • medusa: a free-floating stage (jellyfish) • Many cnidarians have both body plans, corals and sea anemones exist as polyps

18. Stinging Cells • Cnidocytes have nematocysts • nematocysts: discharged when it contacts another object

20. Stinging Cells • Why do they need stinging cells? • They have very flimsy body plan. They must paralyze their prey (sometimes a large fish), so that they can digest it • Dangerous species • Portuguese man-of-war (painful stings) • box jellyfish (can kill within 3-20 minutes)

22. Groups of cnidarians • hydrozoans • Anthozoans • Scyphozoans • cubozoans

23. Types of Cnidarians • Hydrozoans (class Hydrozoa) • mostly colonial • hydrozoans known as hydrocorals secrete a calcareous skeleton, e.g., fire coral • some produce floating colonies • e.g. Portuguese man-of-war

26. Types of Cnidarians • Jellyfish and box jellyfish • scyphozoans—true jellyfish (class Scyphozoa) • considered members of the plankton • medusa is predominant life stage • photoreceptors: sense organs that can determine whether it is dark or light • box jellyfish (class Cubozoa) • box-shaped bells • relatively strong swimmers • tropical • voracious predators, primarily of fish

29. Types of Cnidarians • Anthozoans (class Anthozoa) • include sea anemones, corals and gorgonians • Sea anemones • benthic, all adults are sessile • polyps with a gastrovascular cavity divided into compartments radiating from the central one • though sessile, many can change locations

31. Types of Cnidarians • Anthozoans (class Anthozoa) • Coral animals • polyps that secrete a hard or soft skeleton • scleractinian corals = hard, stony corals • form reefs along with coralline red algae and calcified green algae

34. Types of Cnidarians • Anthozoans (class Anthozoa) • soft corals • polyps that form plant-like colonies

37. Nutrition and Digestion • Gastrovascular cavity: central cavity where cnidarians digest their prey • functions in digestion and transport • waste products forced back out mouth • Many hydrozoans and anthozoans are suspension feeders • Jellyfish and box jellyfish are carnivorous, eat fish and larger invertebrates • Sea anemones generally feed on invertebrates, some large species feed on fish, shallow water species have symbiotic algae

38. Ecological Relationships of Cnidarians • Predator-prey relationships • cnidarians are predators • stinging cells discourage predation • sea turtles, some fish and molluscs prey on hydrozoans and jellyfish • Habitat formation • coral polyps form complex 3-dimensional structures inhabited by thousands of other organisms • coral reefs provide a solid surface for attachment, places for pelagic animals to rest and hide and buffer waves and storms

39. Ecological Relationships of Cnidarians • Symbiotic relationships • Portuguese man-of-war and man-of-war fish • reef-forming corals and zooxanthellae • The zooxanthellae (dinoflagellate algal protist) provide food and oxygen to coral through photosynthesis • Coral provides nutrients and carbon dioxide to algae through respiration • sea anemones... • Have symbiotic relationship with the clownfish • and the hermit crab

41. Phylum Ctenophora • Phylum Ctenophora • Planktonic, nearly transparent • Ctenophore structure • named for 8 rows of comb plates (ctenes) which the animal uses for locomotion • ctenes are composed of large cilia • exhibit radial symmetry • lack stinging cells • bioluminescent

43. Ctenophores • Digestion and nutrition • carnivorous, feeding on other plankton, larval fish and fish eggs • may use branched tentacles in a net pattern, adhesive cells, jellyfish stingers to capture prey

45. Ctenophores • Ecological Role • can effect zooplankton abundance directly and fish populations by preying on fish larvae and eggs

46. Now we will talk about animals with bilateral symmetry – all other animals have this type of symmetry • Bilateral symmetry • body parts arranged such that only one plane through the mid-line of the central axis divides animal into similar right and left halves • allowed for streamline body shape increasing mobility • favored concentration of sense organs at one end of animal (cephalization)

47. Phylum Platyhelminthes • Flatworms • Have flattened, bilaterally symmetrical bodies with a definite head and posterior end • 3 groups • Turbellaria – free living • Trematoda – parasitic flukes • Cestoda – parasitic tapeworms