Cnidarians Phylum Cnidaria: “stinging cell” On earth- since 670 MYA radial symmetry Germ Layers: 2 epidermal (ectoderm) gastrodermal (endoderm) NO ORGAN SYSTEMS No Segmentation Movement: sessile or motile predators Have tentacles- stinging cells (cnidocyts) , nematocysts “thread cells” used as barbs

Structures: One body opening (mouth) for food to enter and wastes to exit Gastrovascular cavity: interior cavity where food is digested & nutrients are circulated around the body Nerve net: net of nerves that allow impulses to travel around the body, senses the environment Label the hydra on your notes! http://www.arkive.org/common-jellyfish/aurelia-aurita/video-10.html

Without Body Systems, how do they survive? Nervous: Cephalization absent; Nerve Net- Skeleton: Hydrostatic- water pressure maintains shape Respiration: Oxygen diffuses into body from water Digestion: mouth, GVC Excretion: simple diffusion into water Circulation: GVC- gastrovascular cavity Reproduction: asexual and sexual, alternation of generations

Cnidarians: Body Forms Polyp: body with tentacles facing upward, sessile Ex: hydra, sea anemone video polyp predation Medusa: body with tentacles hanging downward, motile Ex: jellyfish

Cnidarian Reproduction Asexually: by budding Sexually: usually in medusa form, sperm and eggs are released into water (fertilized egg zygote planula larvaadult) Thousands of gametes are released at a time

Alternation of Generations: Video: medusa releasing from polyp

Checkpoint: List 5 traits that cnidarians share. How many germ layers do cnidarians have? ____ Which are they missing? Are all cnidarians predators? Motile? Describe the specialized cells they have on their tentacles. Describe how a cnidarian consumes and digests food. Describe the two body forms Cnidarians display, and give examples of each type.

Structure:The Polyp and Medusa Stages Epidermis Mesoglea Gastroderm Tentacles Mouth/anus Gastrovascular cavity Mesoglea Gastrovascular cavity Mouth/anus Tentacles Medusa Polyp basal disc: sticky structure at the bottom of polyp ; sessile

Diploblastic - 2 germ layers Epidermis - outer covering (ectoderm) Mesoglea - middle non-living jelly-like layer (missing mesoderm) gastrovascular cavity (endoderm)

Classes of Cnidarians 1. Hydrozoa 2. Scyphozoa 3. Anthozoa

Class Hydrozoa Freshwater & marine. Medusa and polyp colonies which appear to be one organism- different types of polyps work together to serve the entire colony Ex: Hydra, Obelia, Gonionemus Physalia (portuguese-man-of-war) 36:40 Ocean Drifters Asexual repro.-budding. Sexual repro. via gametes

Gonionemus Diagram mouth GVC Gonad mesoglea tentacle

Class Scyphozoa Scyph= “cup” Large- Tentacles up to 70 meters in length All marine Independent medusa forms Lack polyp stage or have for a very short time Ex. Box jellyfish Big Jelly

Class Anthozoa ANTHO=“flower” All polyps-Medusa stage absent Solitary or colonial Some produce protective skeletons All Marine Ex. Sea anemones, corals

Class Anthozoa Sea Anemone Video jewel anenome

Class Anthozoa Metridium Tentacles Mouth Pharynx Septum Gastrovascular cavity

Symbiotic Relationship

Class Anthozoa Corals Polyp secretes protective skeleton of calcium carbonate Polyp retracts when not feeding

Corals Colony of interconnected polyps

Class Anthozoa Meandrina Brain Coral

Class Anthozoa Gorgonia Sea Fan

Class Anthozoa Tubipora Pipe Organ Coral

Class Anthozoa Actinodiscus Mushroom Coral

Class Anthozoa Acropora Staghorn Coral

Coral Reefs Formed over 1000’s of years from successive layers of coral skeletons The underwater equivalent of the amazon jungle- very high species diversity and biomass Reefs contain: sponges, colonial hydrozoans, anemones, many varieties of coral, fish, many types of worms we’ve not discussed…not to mention bryozoans, ctenophores, protists, bacteria, etc, etc…

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coral Reef Ecosystem Photo © McGraw-Hill Higher Education, Barry Barker, Photographer

Cnidarian Cladogram Anthozoa Scyphozoa Cubozoa Medusa cuboidal Loss of medusa Hydrozoa Polyp stage reduced Septa divide gastrovascular cavity Radial symmetry, cnidocytes, planula larva

Checkpoint Cnidarians are diploblastic, what does this mean? What is the mesoglea? How are Hydrozoans different from other classes of cnidarians? List examples of Hydrozoans. What are scyphozoans, do they have a polyp stage? Anthozoans are known as the ______________ animals. Give examples of anthozoans. What is an anthozoan’s protective skeleton made of? Why are coral reefs important?

The End