Cnidaria By: Michael Dang Annie Ma David Shia

Phylum Phylum: Cnidaria Families: Hydrozoa- polyp and medusa stages in reproductive cycle (Ex: corals) Scyphozoa- reduced polyp stage (Ex: jellies) Cubozoa- box shaped polyps (Ex: box jellies) Anthozoa- no medusa stage (Ex: corals)

Sample Animals Jellyfish Corals Hydras Box Jellyfish Anemone Sea Wasp Sea Pens

Body Cavity Single Body Cavity diploblastic (two membranes: ectoderm/endoderm) used for digestion and respiration They contain one cavity that operates as both their mouth and anus Polyp- mouth cavity is on top Medusa- mouth cavity is on bottom

Body Symmetry Radial Symmetry

Nervous System Cnidaria lack a brain and a central nervous system, but they do have a net of neurons Ocelli: organs that sense direction of light Statocysts: means of regulating tilt and acceleration in cnidaria

Circulatory System None

Digestive System All are carnivorous Absorb nutrients by filtering water Tentacles put the prey into the mouth where digestive enzymes are used to break prey down into organic substances

Excretory System Present Anus/ mouth Diffusion

Locomotion/ Musculature Has muscle, but really weak in most Cnidaria. Strong enough to direct movement in a current Jet Propulsion: water is squeezed and then released from the cavity using coronal muscles Some sea anemone can creep along

Skeletal Type Cnidaria bodies are composed of the jelly-like substance called mesoglea Most can form a hydrostatic skeleton, in which the cavity fills with water, expanding the body of the cnidaria Coral have exoskeletons composed primarily of calcium

Sensory Structures/ Features Simple sensory structures Responds to touch through cnidocytes, stinging cells located on the tentacles Nematocytes, the stinging capsule of a cnidocyte, releases a poisonous thread when triggered by a chemical or touch

Reproduction Sexual and asexual reproduction Cnidaria usually have 2 main forms in their life cycle: the polypoid stage is diploid, and the mature polyp is usually found in colonies. Medusae are produced asexually through budding, which reproduce sexually to form polyps.

Gas Exchange Cnidarians lack the organs for gas exchange, so they just let the gas from the water diffuse through their bodies

Other The amount of poison from a sea wasp, a cubozoan, is powerful enough to kill 60 people! Coral is really a colony of really small polyps! Many species of jellyfish are bioluminescent!

QUIZ TIME 1.What are the two forms of a Cnidaria’s life cycle? a.Polyp and Cnidocyte b.Medusae and Polyp c.Polyp and Hydrozoa d.Cubozoa and Medusae e.None of the above

Answer B Medusae and Polyps Medusae= tentacles facing down. Motile. Polyp= tentacles facing up. Stationary.

QUIZ TIME 2. What mechanism do Medusae use to move through the water? a.Current b.Jet Propulsion c.Latching on to other animals d.A and B are both correct e.All of the above

Answer D Current and Jet Propulsion Medusae have relatively weak muscles, so they must use the current to help them move Jet Propulsion= uptake and release of water to create the thrust force to make them move forward.

QUIZ TIME 3. What is the Mesoglea? a.The excretory waste of the Cnidaria b.The nervous system of the Cnidaria c.The name of the colonies that the polyps form d.The tentacles of the jellyfish e.The substance that the Medusae’s body is composed of

Answer E The substance that the Medusae’s body is composed of

QUIZ TIME 4. What systems are absent in Cnidaria? a.Skeletal and Nervous b.Excretory and Digestive c.Nervous and Circulatory d.Circulatory and Digestive e.Musculature and Reproductive

Answer C Nervous and Circulatory Cnidaria have no brains, thus no nervous system, but do have a simple sensory network throughout the body. They do not need a circulatory system and regulate substances through diffusion.