Who, What, When, Where, Why, and How of Lower 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? Karleskint Small Turner Chapter 8 Lower Invertebrates What Are Animals? Animals: 1.are multicellular distinguishes them from bacteria and most protists 2.have eukaryotic cells without cell walls distinguishes them from bacteria, fungi, algae and plants 3.cannot produce their own food, depend on other organisms for nutrients 4.can actively move at least at some point during their life cycle 5.invertebrates = animals that lack a vertebral column (backbone 6.vertebrates animals with a vertebral column 7.majority of animals in sea are invertebrates The first animals we will talk about are sponges They are assymetrical no symmetry No true tisses 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 Sponge Structure and Function Body is built around a system of water canals ostia: tiny holes or pores through which water enters the sponges body spongocoel: spacious cavity in the sponge into which water flows osculum: large opening through which water exits from the spongocoel Water exits through osculum Water enters through small pores (ostia) Spongocoel (choanocyte) Collar cell Spongocoel Archaeocyte Spicule Pinacocyte Pore cells Ostium Flagellum Collar Food particles Stepped Art Fig. 8-1, p. 193 Sponge Structure and Function Lacking tissues, sponges have specialized cells collar cells (choanocytes) use their flagella to provide force for moving water through the sponges 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 Sponge Structure and Function Structural materials spicules: skeletal elements that give support to a sponges 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 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 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 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 Now we will talk about animals with radial symmetry Phylum Cnidaria Animals with stinging cells Include jellyfish, hydroids, corals and sea anemones Named for their cnidocytesstinging cells Cnidocytes are used to capture prey and protect the animal 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 Stinging Cells Cnidocytes have nematocysts nematocysts: discharged when it contacts another object 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) Groups of cnidarians hydrozoans Anthozoans Scyphozoans cubozoans 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 Types of Cnidarians Jellyfish and box jellyfish scyphozoanstrue 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 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 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 Types of Cnidarians Anthozoans (class Anthozoa) soft corals polyps that form plant-like colonies 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 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 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 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 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 Ctenophores Ecological Role can effect zooplankton abundance directly and fish populations by preying on fish larvae and eggs 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) 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 Flatworms Types of flatworm turbellarians are mostly pelagic, and are common members of meiofauna (invertebrates living between sediment particles) turbellarians have sensory receptors in head region to detect light, chemicals, movement and help maintain balance flukes usually have complex life cycles tapeworms live in the hosts digestive tract Flatworms Ecological role of flatworms Turbellarians: turbellarians funnel nutrients to higher trophic levels prey for higher-level consumers Parasitic flatworms: can regulate population size by lowering fitness of host Lophophorates Lophophorates are sessile animals that lack a distinct head Possess a lophophore: arrangement of ciliated tentacles that surround the mouth, used for feeding, gas exchange 3 phyla of lophophorates: Phoronida (phoronids) Ectoprocta (bryozoans) Brachiopoda (brachiopods) Phoronids Small, worm-like animals Secrete a tube of leathery protein or chitin that can be attached or buried in bottom sediments Catch plankton and detritus with mucus- coated tentacles Can reproduce sexually or asexually (budding, transverse fission) Have a planktonic larval stage Bryozoans Small, abundant, colonial animals Most live on rocks, shell, algae, mangroves, etc. in shallow water Along with hydroids, rank among the most abundant marine epiphytic animals Most are hermaphroditic brooders Larvae are planktonic, settle to form new colonies Brachiopods Most brachiopods (lamp shells) are benthic and live in shallow water changed little since they evolved 400 million years ago Have mollusc-like, bivalve shells valves differ in size and shape, and are dorsal and ventral a pedicle (fleshy stalk) attaches the shell or is buried Gather detritus/algae with lophophore Generally have separate sexes; larvae are planktonic and settle in hrs. Ecological Roles of Lophophorates As a group, they are filter feeders Food for many invertebrates, especially molluscs and crustaceans Largely responsible for fouling ship bottoms