The Cnidarians are a diverse group of aquatic life with more than 9,000 different species. They are most common in oceans, but are also found in freshwater habitats. Discover new information about jellyfish, corals, and sea anemones by exploring this page!
Characteristics of the Phylum Cnidaria:
Cnidarian's have 2 Different Body Forms:
Characteristics of the Phylum Cnidaria:
- They are invertebrate organisms
- They are radially symmetrical
- They have a multicellular body with very few tissues and no organs
- They have 2 embryonic layers, the endoderm and ectoderm, which makes them Diploblastic
- Their body contains a Gastrovascular Cavity (not a true body cavity), with one opening which is the mouth and the anus
- Reproduction can be sexual and asexual
- Lives in mostly aquatic, marine environments
- They are filter feeders and are also carnivorous
Cnidarian's have 2 Different Body Forms:
Polyp
|
Medusa
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They have 5 Different Classes Within the Phylum:
Class Hydrozoa (Hydras)
- Cnidocytes are present in the epidermis
- Many polyps are colonial and produce medusae
- Mostly marine species, with some freshwater species
- A colony of polyps that have "zooids" with a specialized function
- Floats on the surface on a gas-filled bladder
Scyphozoa (Jellyfish)
- Medusa are the most common body form
- Cnidocytes are present in the gastrodermis and the epidermis
- Marine species
Staurozoa
- Eight tentacles surround the mouth
- Attach themselves to things by using adhesive disks
- Only capable of sexual reproduction
- Marine species
- Only have polyp body forms
- Attach themselves to rocks and seaweed and are rarely free-floating
Cubozoa (Box Jellyfish)
- Medusa is the most common body form
- Their medusa is cube-shaped and their tentacles only hang from each corner of the bell
- Marine species
Anthozoa (Corals and Sea Anemones)
- Colonial Polyps
- Internal biradial and bilateral symmetry
- Can be monoecious and dioecious
- Capable of sexual and asexual reproduction
- Form symbiotic relationships with algae and other organisms
- Most are sessile, but some can move
Sea Anemones and Clownfish: A Symbiotic Relationship
- The clownfish are covered in a protective mucus, so they don't get stung by the anemone
- They represent a mutual, symbiotic relationship
- The clownfish gets the anemones food leftovers and they anemone gets cleaned up by the clownfish
- The Sea Anemones are mostly polyps