Chapter 28 Simple Invertebrates

28-1: Sponges Domain: Eukarya Kingdom: Animalia Phylum: Porifera

General Characteristics No symmetry No tissues / organs Cells can recognize other cells Reorganize when separated Sessile: do not move as adults Diameter ranges from 1cm to 2m

Body Characteristics Ostia: Pores on outer wall Osculum: Large hole for water to exit Choanocytes: cells with flagella that line internal cavity Move water through body cavity Trap food particles and digest Also called Collar Cells Amoebocytes: cells that move around in sponge body to transport nutrients / wastes

Pore cells = Ostia Collar cell = choanocyte

Sponge Feeding

Sponge “Skeletons” Most have Spicules: tiny needles made of calcium carbonate or silica Some sponges have spongin: flexible protein fibers

3 Classes of Sponges Calcareous Sponges Glass Sponges Demosponges Skeletons made of calcium carbonate spicules Glass Sponges Spicules made of silica Demosponges Skeletons made of spicules and spongin

Asexual Reproduction Can regenerate when cut into pieces Fragmentation Budding: smaller individuals grow off sides of larger individual Form gemmules: when living conditions become too poor, amoebocytes encase in protective shells to survive

Sexual Reproduction Most sponges are hermaphrodites Sperm released into water Sperm cells from another sponge enter through pores Larvae develop from fertilized eggs and swim away

Sponge Defenses Sponges are soft (easily eaten) Sponges are sessile (can’t swim away) Protect selves by producing chemicals These chemicals have been used by humans for Antibiotics Pain killers / Sedatives Cancer treatments

28-2: Cnidarians Two body forms: Polyps are sessile… Medusa: free-floating umbrella-like Polyp: tubelike and attached at base Polyps are sessile… Attach to floor / object with Basal Disk Both show radial symmetry Tentacles surround mouth Enters into gastrovascular cavity

2 layers of cells Ectoderm on outside Endoderm on inside Mesoglea: layer of “jelly” between the 2 layers Cells arranged into tissues

Cnidocytes Cnidocytes: Stinging cells on tentacles Contain Nematocysts: small, barbed harpoons Some nematocysts have deadly toxin, some with chemicals to just stun Used for defense and to spear prey Tentacles pull food into mouth

3 classes Hydrozoans Scyphozoans Anthozoans Ex: Hydra, Portuguese-Man-of- War Scyphozoans Ex: Jellyfish Anthozoans Ex: Sea Anemones, Corals

Hydrozoans Most are Colonial Life cycle includes both polyp and medusa forms Live in freshwater and marine Freshwater example: Hydra Marine hydrozoans are among most toxic (deadly to humans)

Hydra: freshwater Hydrozoans Most of life is individual polyp Stick to surfaces with sticky secretion from basal disk (bottom) Can glide on basal disk or tumble

Reproduction in Hydrozoans Most capable of sexual reproduction Some are hermaphrodites Can reproduce asexually also budding

Scyphozoans “True” Jellyfish Can be small (thimble-sized) to extremely large (queen-sized mattress) Go through polyp stage at some point in life cycle

Anthozoans Corals and Sea Anemones Have symbiotic algae living in cells to help provide energy Sea Anemones are soft-bodied Corals secrete calcium carbonate outer skeletons Only top layer is alive, rest is old skeletons of dead corals Build up into reefs

28-3: Flatworms & Roundworms

Flatworms Phylum Platyhelminthes More complex than sponges and cnidarians Have middle tissue layer Tissues organized into organs Bilateral symmetry Cephalization

Since they are flat… Each cell close enough to outside to get O2 and release CO2 Gastrovascular cavity branched and close to all tissues (nutrients to cells easily) Still have just 1 opening

3 classes Turbellaria: Free-living Most marine Freshwater: Planaria

Planarian Feeding Use muscular tube that extends from center of GVC Called Pharynx Eat small protists or dead / dying animals

Planaria Reproduction Attach posterior end to rock, pull apart into 2 Regenerate Sexually reproduce by exchanging sperm with another planarian Hermaphrodites

2. Cestoda Parasitic Commonly called Tapeworms Hooks and suckers on head to attach inside host’s intestine Absorb nutrients from host Produce proglottids: string of rectangular body segments that break off in reproduction

Can grow to be 40 ft. long

3. Trematoda AKA “Flukes” Parasites: Live in host (endoparasites) Live on host (ectoparasites) Ex: Schistosoma Disease: Schistosomiasis

Enter through skin (hookworm) and burrows to blood vessels to lay eggs Block blood vessels (internal bleeding and liver damage)

Roundworms Phylum Nematoda Have pseudocoelom Simplest animals with one-way digestive tract (mouth and anus!) Most microscopic One square yard of forest soil can have 3 million nematodes

Pseudocoelom “False” body cavity Filled with fluid to act as simple respiratory and circulatory systems O2, CO2, nutrients flow through body

Can be human parasites… Ascaris lumbricoides Infects lungs, gall bladder, pancreas Trichinella spiralis Infects muscles

Elephantitis: blockage of lymph system by nematode enters through skin in water