Chapter 8 Lower Invertebrates

What Are Animals? Animals: are multicellular have eukaryotic cells without cell walls cannot produce their own food, depend on other organisms for nutrients can actively move invertebrates = animals that lack a vertebral column (backbone) vertebrates – animals with a vertebral column majority of animals in sea are invertebrates

Body Structure Dorsal – Top Ventral – Bottom/belly Anterior – Head Posterior - Tail

Body Symmetry Asymmetry – No symmetry Radial – Arrangement of body parts around a central axis - Top & bottom, No front, back, or right & left sides – Allows for organism to take in stimuli from all sides

Bilateral symmetry – 2 similar halves on either side of a central plane Adaptation for movement

Cephalization Concentration of sensory & brain structures in the Anterior region No-cephalization

Sponges Phylum Porifera 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

Sponges have specialized Cells but NO Tissues Most primitive animals on Earth

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

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 Amoebocytes: Cells that resemble amoebas, and can move through sponge body Transport materials

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 spongin Spongin: A protein that forms flexible fibers

Sponge Structure and Function Sponge size and body form Size is limited by water circulation Asconoid: Simplest form; tubular and always small, found in clusters Syconoid: Sponges that exhibit the first stages of body-wall folding Leuconoid: Sponges with the highest degree of folding, which have many chambers lined with collar cells

Osculum Ostia Choanocyte Spicules Amoebocyte

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 Large particles are engulfed and digested by pinocytes and archaeocytes Collar cells trap ~ 80% of food which consists of small particles (0.1 to 1.0 micrometers in size) Sponges are one of the few animals that can capture such small sized particles

Sponge Structure and Function Reproduction in sponges Asexual reproduction Budding: Group of cells on the outer surface of the sponge develops and grows into a tiny new sponge, which drops off and establishes itself Fragmentation: Production of a new sponge from pieces that are broken off by physical processes, e.g., waves, storms, predators Sexual reproduction Most sponges are Hermaphrodites Larval stage is called a planktonic Amphiblastula

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

Ecological Roles of Sponges Sponges and nutrient cycling Boring sponges (family Clionidae) recycle calcium as they burrow into coral and mollusc shells

Sponge Dye in the Ocean http://www.youtube.com/watch?v=8ueKlShb9Ls

Phylum: Cnidaria Jellyfish, Anemone, Corals Kingdom: Animalia Phylum: Cnidaria Jellyfish, Anemone, Corals

Cnidarians: Animals with Stinging Cells Phylum Cnidaria Include jellyfish, hydroids, corals and sea anemones Named for their Cnidocytes—Stinging cells Cnidocytes are used to capture prey and protect the animal

Organization of the Cnidarian Body 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)

Stinging Cells Cnida: Stinging organelle within a cnidocyte, which may function in locomotion, prey capture, or defense Nematocysts: Spearing type cnida, which are discharged when the cnidocill—a bristle-like trigger—contacts another object

Stinging Cells Stinging cells also triggered by certain chemical substances released by prey Dangerous species Box jellyfish (can kill within 3-20 minutes)

Kingdom: Animalia Phylum: Cnidaria Class: Hydrozoa “water animals”

Types of Cnidarians Hydrozoans (class Hydrozoa) Mostly colonial Colonial forms contain 2 types of polyp: Gastrozooid = Feeding polyp Gonangium = Reproductive polyp Hydrozoans known as hydrocorals secrete a calcareous skeleton, e.g., fire coral Some produce floating colonies e.g. Portuguese man-of-war

Portuguese Man of War http://www.youtube.com/watch?v=xTgLTbXJrfM&list=PL355D512277EFFA06&index=23

Ex: Physalia Portuguese man-of-war Colony of medusae and polyps Gas-filled float: Tentacles measure up to 65ft Preys mostly on small fish-poison can be painful and even fatal to humans

Class: Scyphozoa “cup animals” True Jellyfish Phylum: Cnidaria Class: Scyphozoa “cup animals” True Jellyfish

Phylum: Cnidaria Class: Scyphozoa Cup animals Jellyfish Medusa is the dominant form of the life cycle Pulsating motions of the cup propel the jellyfish through the water Some nematocysts cause severe pain and even death to humans

Types of Cnidarians 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

Class: Anthozoa “flower animals” Sea Anemone & Coral Phylum: Cnidaria Class: Anthozoa “flower animals” Sea Anemone & Coral

Types of Cnidarians Anthozoans (class Anthozoa) Include sea anemones, corals and gorgonians Sea anemones Benthic, all adults are sessile Though sessile, many can change locations

Phylum: Cnidaria Class: Anthozoa “Flower Animals” Polyp form dominant Sea Anemone 1. Attach themselves to rocks and other submerged objects 2. Feed on fishes and other animals

Corals 1. Small polyps live in colonies 2. calcium carbonate skeleton 3. 30 degrees N or S of the equator 4. Shallow depths in warm, clear water 5. Zooxanthellae

Types of Cnidarians Anthozoans (class Anthozoa) Coral animals Polyps that secrete a hard or soft skeleton 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 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

Reproduction Scyphozoans in adult jellyfish and box jellyfish, sexes generally separate medusae (sexual stage) release gametes into the water column for fertilization planula larvae settle, grow into polyps, and reproduce medusa-like buds asexually immature buds are released into the water column to grow into mature medusae

Ecological Relationships of Cnidarians Predator-prey relationships Cnidarians are predators Sea turtles, some fish and molluscs prey on hydrozoans and jellyfish

Ecological Relationships of Cnidarians Symbiotic relationships Portuguese man-of-war and man-of-war fish Reef-forming corals and zooxanthellae Algae provide food and oxygen to coral through photosynthesis Coral provides nutrients and carbon dioxide to algae through respiration Sea anemones... and Clownfish and the Hermit crab

Phylum: Ctenophora Comb jellies

Ctenophores Phylum Ctenophora Planktonic, nearly transparent Ctenophore structure Named for 8 rows of comb plates which the animal uses for locomotion Are composed of large cilia Exhibit radial symmetry Lack stinging cells – Adhesive cells (sticky) Bioluminescent

Phylum: Ctenophora Comb jelly - eight comb like rows of cilia Move through water by beating their cilia Colloblasts-secrete a sticky substance that binds to their prey Apical organ-senses orientation in the water Most hermaphroditic Bioluminescence-production of light Occur in large swarms near the surface of the ocean

Neon Killers http://www.youtube.com/watch?v=39qe0EajbIA&list=PL355D512277EFFA06&index=106

The Evolution Of Bilateral Symmetry Body parts arranged such that only one plane through the mid-line 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)

Flatworms Have flattened, bilaterally symmetrical bodies with a definite head and posterior end

Flatworms Types of Flatworm Turbellarians are mostly pelagic, and are 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 host’s 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

Ribbon Worms Phylum Nemertea Most are benthic Resemble flatworms but are longer with thicker bodies Sexes are separate, fertilization external Carnivorous – Feed on annelids and crustaceans Capture prey with proboscis (tube extending from mouth)

Ribbon Worms Ecological role of ribbon worms Prey organisms for higher consumers Burrowing in sediment moves nutrients to surface Abandoned burrows can serve as habitat