L6 Cnidarians Flashcards
How many body layers in the cnidarians?
2, is diploblastic
What is the mesoglea?
Tissue between the two body layers, is connective tissue and acts as a hydrostatic skeleton
Do they have organs?
Limited
What are the two forms in which they can exist?
Polyp or medusa, are the same, but reversed
What are cilary receptors?
For detection in the environment
What are interstitial cells?
Can transform into other cells
What are neutrons?
Form the nervous system, a nerve net
What are enzymatic gland cells?
Discharges enzyme into the gut?
What are muscle cells?
Take up products of digestion, where the process of breakdown is completed.
How do the nematocysts, stinging cells, function?
Designed to capture and sting the prey, On stimulation, there is a build up of Ca, which causes a change in the osmotic pressure, meaning water floods into the cell, which opens, shooting the barb out - cannot be used, but can be replaced
what are glaucus?
A species of sea slug that eats the cnidarians, and can retain the nematocysts, and use them for its own means
What mode of feeding do most cnidarians have?
Carnivorous, captured in the tentacles and transferred to the mouth
What are the different classes of the cnidarians?
Hydrozoans
Schyphozoans
Cubozoans
Anthozoans
How do the hydrozoans live?
Usually are colonial, other than the hydra, sometimes show secondary polymorphism.
What is the role of the medusa forms in the Hydrozoa?
Reproducing, is sometimes retained, when no polymorphism. Juvenile is medusa
What are planula?
free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species
What are siphonophores?
Most sophisticated of the hydrozoans, marked as one of the 4 pinnacles of social evolution, for example, Portuguese man of war. Rely on currents for movement, all part shave individual roles, working together as a whole.
What are the schyphozoans?
True jellyfish
Which stage is dominant in the schyphozoans?
The medusa stage
What is the rhopalium?
Formed of two layers of muscle, one I on the surface, they form contractile forces, so it can pulse the umbrella, allowing it to move and swim. Still has to rely on currents
What are stantocysts?
Allow the jellyfish to sense gravity
What are pigment cup ocelli?
Form of simple eyes that allow the jellyfish to detect light and dark
What could happen to jellyfish populations if sea temperatures increase?
Can move into new areas, and cause a boost in populations, boasts a problem for tourism and for other animals
What are the cubozoa?
Box jellyfish
How do box jellyfish differ from true jellyfish?
Are active swimmer, up to 2m/s, are smaller and highly toxic
What do box jellyfish feed on?
Mostly small fish, but can cause human fatalities
What are the anthozoa
Sea anemones, corals
What form are the anthozoa found in?
In the polyp stage, can be colonial or solitary
How do anthozoa reproduce?
Medusa stage is absent, gametes are released into the sea
May be asexual, by pedal laceration
May be sexual, are hermaphrodites, so produce egg and sperm at different times. Fertilisation takes place in the gastrovascular cavity, or in the sea
What are the symbiotic relationships seen in anthozoa?
With clown fish, the clown fish lives in the anemone tentacles, doesn’t get stung by nematocysts. Both will benefit from this intereaction
Relationship with zooxanthella, found in reefs
What is the skeleton of corals composed of?
Caco3
