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The Fascinating World of Cnidarians

The phylum Cnidaria contains such creatures as jellyfish, anemones, siphonophores and corals. Together, they consist of around 13,000 living species - surprisingly simple, yet beautiful organisms.

2021-04-13 19:00:00 - Natural World Facts

The importance of these cnidarians cannot be understated. Coral reefs are formed of many millions of cnidarians and are home to staggering biodiversity. Jellyfish are important predators in the open ocean food web, but they serve as food for many other species as well.


Sea anemones fulfil a similar role but in the shallows, also serving as hiding places for clownfish. Thus, this unique and abundant group of creatures is integral to the function of many marine communities, from the open ocean to coasts and the benthic zone of the deep sea.


00:00 - An Introduction to Cnidarians

01:04 - The Structure of Cnidarians

01:57 - Cnidarian Polyps

02:09 - Cnidarian Medusae

02:19 - The Life Cycle of Moon Jellyfish

03:10 - The Diversity of Jellyfish

03:23 - The Lion's Mane Jellyfish

03:39 - The Role of Cnidarians in the Food Web

04:29 - Nematocysts Explained

05:13 - The Portugese Man-o-War

06:18 - Colony Organisms: Siphonophores

06:37 - Colony Organisms: Corals

06:54 - The Importance of Corals

07:33 - Symbiosis in Corals: Zooxanthellae

08:23 - Symbiosis in Anemones: Crabs

08:49 - Symbiosis in Anemones: Reef Fish

09:12 - Symbiosis in Medusae

09:27 - The Importance of Cnidarians

09:55 - Conclusion

10:31 - The Deep Sea Hub

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