Sponges & Cnidarians Sponges ● Kingdom: Animalia – Phylum: Porifera (sponges) ● Simplest invertebrates ● Asymmetrical (no symmetry!) ● No tissues, gut or nerves 2 H ow Do Sponges Eat? ● Filter feeders: feed on tiny plants and animals ● Water carries food into the sponge through pores (ostia) – Ostia: holes on the outside of the body ● Inside the sponge, collar cells remove food from the water – Collar cells: special cells that line the central cavity of the sponge; they digest food ● The water exits through an osculum – Osculum: hole at the top of the sponge 3 Sponge Anatomy Where does the water enter? Where does the water exit? What structure on the collar cells pushes the water up? 4 Body Part Abilities ● If a part of a sponge is broken off, the missing part can regenerate, or grow back ● If a sponge is broken into pieces, new sponges could form from each piece ● If you force a sponge body through a strainer, the separated cells could come back together and reform the same sponge! 5 Kinds of Sponges ● All live in the water (most in salt water) ● Come in different shapes/sizes ● Most sponges have a skeleton made of hard fibers called spicules ● Grouped by their type of skeleton – Barrel sponge – Tube Sponge – Finger Sponge – Vase Sponge 6 Cnidarians ● Pronounced “nigh-dare-e-ins” ● Kingdom: Animalia – Phylum: Cnidaria ● Invertebrates that have stinging cells ● More complex than sponges – Have complex tissues, a gut & simple nerves ● Include: jellyfish, hydrozoa, sea anemones and coral ● 7 Two Body Forms ● Cnidarians have ONE of the two body forms: – Medusa: swim through the water – Polyp: attach to a surface ● Some change forms at different times in their life 8 Special Cells ● All cnidarians have tentacles covered with stinging cells – Nematocysts: stinging cells that release spears into an organism when it brushes the tentacles ● Some can release poison ● Used for protection and to catch food ● 9 Kinds of Cnidarians We split them into four classes: ● Kingdom: Animalia ● Phylum: Cnidaria ● Class: – Hydrozoa (Hydra) – Scyphozoa (Jellyfish) – Anthozoa (Anemones & corals) – Cubozoa (Box Jellies) 10.