MARINE SCIENCE PHYLUM CNIDARIA What are Cnidarians?
Post on 16-Dec-2015
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Soft-bodied animals with stinging tentacles
Ex: Jellyfish, anemones, corals, hydras
Over 9,000 species
Body forms:Medusa, What Shape is this structure?
Polyp, What Shape is this structure?
Single opening surrounded by tentacles Is both mouth and anus
Simple Nervous systemNo brain
INTERNAL STRUCTURE: Epidermis
Mesoglea (Jelly-like material in between layers)
Gastrodermis
Which layer is the inner layer?
Gastrovascular cavity: internal space where digestion takes place
DEFENSENematocysts: Stinging
structures located on tentacles
Spring loaded poison-filled darts
Captures and paralyzes prey Defense
Jellyfish sting!
**Not all tentacles have nematocysts; some used for reproduction, feeding
REPRODUCTION
Most Cnidarian life-cycles involve an alteration of generations:
two different body forms
dominant and conspicuous medusa form
smaller polyp form, often restricted to the larval stage.
Jellyfish reproduce sexually, and individuals are either male or female. The reproductive organs (gonads) develop in the lining of the gut.
CLASSES OF CNIDARIANS:There are four classes of Phylum
Cnidaria:
1) Class Hydrozoa– “water animals”
2) Class Scyphozoa– “cup animals”
3) Class Anthozoa– “flower animals”
4) Class Cubozoa– “cube animals”
CLASS HYDROZOA“WATER-ANIMALS”
Can have polyp, medusa or both shapes; often have alternation of generations
Mostly colonial*
Some live in fresh water
Ex: Portuguese Man-O-War, Hydras
*live in colonies
CLASS SCYPHOZOA“CUP-ANIMALS”
True Jellyfish
Adult stages have medusa shaped bodies
Tentacles can be over 30 m long in some species!!
Some can cause painful stings
CLASS ANTHOZOA“FLOWER-ANIMALS”
Sea anemones and corals (hard and soft)
Only polyp-shaped bodies
Usually sessile
Coral polyps secrete a calcium carbonate skeleton for protection
Symbionts with photosynthetic algae
CLASS CUBOZOA
Cubozoans are the box jellies. They have a cubical shape when viewed from above
Their tentacles are evenly spaced
This is the smallest class in terms of species
Some box jellies contain deadly toxins in their nematocysts
TREATMENT OF STINGS
First: Carefully remove the tentacles. As long as tentacles remain on the skin, they will continue to discharge venom.
Second: Apply meat tenderizer, vinegar, tobacco or sodium bicarbonate
If stung by a box jelly, seek medical attention immediately! An antivenom is available to prevent mortality.
Don’t rub the sting site!
Don’t use: Alcohol or human urine. These actually stimulate stinging cells and may increase pain and cause severe skin reactions.
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