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17 Cards in this Set
- Front
- Back
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What are Cnidarians? |
They sting. Diploblasts Aquatic Jelly fish, corals, sea anemones etc Benthic or pelagic Single or colonial |
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Why are they important? |
Tourism Food Power stations Eat fish larvae Kill farmed fish with toxins Biotechnology |
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Cnidarians design |
Medusa - jelly fish Polyp - sea anemone
Radially symmetrical Tentacles encircle mouth at one end Gastro-vascular cavity No anus Early nerve nets - able to coordinate moment |
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Cnidocytes and Nematocysts |
Stingers Nematocysts inside cnidocyte Coiled tube and nucleus inside a cavity and held under pressure Stimulates by Ca2+, once triggered shoots out. May contain venoms which can kill or stun. |
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Gas exchange, reproduction |
Diffusion Sexual, planula larva Asexual, budding (hydrozoans) |
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Skeleton |
Made of chitin or CaCO3 |
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4 classes of Cnidaria |
Hydrozoans - hydra like creatures Scyphozoans - true jelly fish Cubozonas - cube type jellyfish Anthozoans - corals and anemones |
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Hydrozoa |
Most primitive Polyp (adult polyp) no medusae Small, often colonial Thin, acellular mesoglea No specialised organs Chitin? For support Reproduction by bidding or gamete release Highly diverse |
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Life cycle of Obelia |
Colony has medusa bud reproductive and feeding polyp Medusa becomes intermediate and produces speed and eggs to then produce blastula then planula to start new colony. |
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Scyphozoans |
True jelly fish Both polyps and medusae (dominant) Not colonial Thick mesoglea; has some amoebocytes Complex gastrovascular cavity - central stomach + 4 gastric pouches, ciliates Complex life cycle Motile but slow Can be large 1.5 diam.
Example aurelia |
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Life cycle of Aurelia |
Makes and females. Striation, dividing horizontally. Young cells at bottom old cells at top, eventually the old cells at the top pop off and then grow into medusa via ethryra. Strobilization |
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Cubozoa (stingers) |
Box shapes medusa ~20 spp.
Reproduction: Medusae release gametes, separate sexes, polyp develops into medusa, no strobilization. Unusual larval form, pear shaped, no ephryra.
Have rhopalia- enables them to detect prey |
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Anthozoa |
Sea anemones Only polyps Large, conspicuous groups Solitary or colonial Well developed musculature of body wall Complex gastrovascular cavity; mesenteric filaments Bilaterally symmetrical; radial only apparent
Corals use epidermal hairs to create water vortices |
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Ctenophora |
Comb jellies/ sea gooseberries Microscopic, often translucent and have many colours All marine Always small Carnivorous 2 tentacles +/- tentillum Tentacles opposite mouth Trap prey with species lasso cells Cydippid larvae Anal pore, through gut No cnidocytes |
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Ctenophora features |
Bilaterally symmetrical 8 rows comb plates for movement Well developed nerve net Thick mesoglea Gut - beaches canals Hermaphrodite Gonads in gastrodermis No planula larva |
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Ctenophore predation |
Their sting cell is more like a harpoon or lasso They are also able to tell their direction in swimming unlike cnidarians |
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Summary Scyphozoa and Cubozoa features |
Medusa is dominant Exclusively marine Usually large Complex gastrovascular cavity GV is ciliated = quasi-circulation Mesoglea is thick Sense organs Separate sexes Complex and varied life cycles |
