Sunday, February 18, 2007

Feeding, Respiration, and Excretion in a Cnidarian


Cnidarians have tentacles that are around the mouth which help them to catch and eat food, they use their nematocysts to fire out barbs or toxins at the prey to kill, injure, or paralyze them. Almost all cnidarians are carnivores, and feed mainly on shrimps, amphipods, plankton, and any other small organism that gets trapped in the tentacles. Once the prey is entangled in the discharged nematocysts it is moved into the mouth and digested in its gastrovascular cavity.

As you can see in the photo this green sea anemone has been feeding. You can see it has some substance in its mouth in the centre.


Jellyfish like most Cnidarians breathe through gas exchange over their entire body surface. They do not have lungs or gills like most other marine species do. It would certainly be interesting if us humans could breath through our skin!


The cnidarians have a canallike cavity in their two-layered bodies for the ingestion, digestion, and egestion of food and wastes. Gaseous wastes are eliminated by diffusion, and solid wastes in dissolved or undissolved form pass out through an opening in the body wall that has 2 purposes of food intake and waste elimination.


Leslie Lim said...

I read your blog.I thought it was great.. Hope you have a great day. God bless.


Noufel S said...

Very helpful

nejita said...

Thanks a ton

sarah lee said...

I really enjoyed reading your article. I found this as an informative and interesting post, so i think it is very useful and knowledgeable. I would like to thank you for the effort you have made in writing this article.

myopinion said...

it is informative . i have little bit confusion that how they excrete ? could you further elaborate this concept?

Carolina Lopez said...

I found this very helpful. I'm giving a class on Cnidaria as a project and its terrifying. Thank you for helping ease my anxiety.

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