Cnidarians
KNOWN SPECIES
15,082
0.64% of our world's living things are cnidarians
CHARACTERISTICS
- animals without a backbone (invertebrates)
- have stinging cells in their tentacles, which they use for defense and to capture prey
SIZE RANGE
Less than 0.04 inch to over 164 feet (1 millimeter to over 50 meters)
WHERE THEY LIVE
- in oceans
- a few in fresh water
Here are just SOME of the world’s cnidarians:
![Sticker about size](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_size_sticker/5943355-2-eng-US/cnidarians_size_sticker_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_size_sticker/5943355-2-eng-US/cnidarians_size_sticker_full_990.png 600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_size_sticker/5943355-2-eng-US/cnidarians_size_sticker_full_1468.png 600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_size_sticker/5943355-2-eng-US/cnidarians_size_sticker_full_1980.png 600w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_size_sticker/5943355-2-eng-US/cnidarians_size_sticker_full_2475.png 600w)
symmetrical brain coral
SCIENTIFIC NAME:
Pseudodiploria strigosa
![Perfectly circular ball of coral](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_symmetrical_brain_coral/5940962-1-eng-US/cnidarian_symmetrical_brain_coral_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_symmetrical_brain_coral/5940962-1-eng-US/cnidarian_symmetrical_brain_coral_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_symmetrical_brain_coral/5940962-1-eng-US/cnidarian_symmetrical_brain_coral_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_symmetrical_brain_coral/5940962-1-eng-US/cnidarian_symmetrical_brain_coral_full_1980.png 1980w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_symmetrical_brain_coral/5940962-1-eng-US/cnidarian_symmetrical_brain_coral_full_2475.png 2400w)
Portuguese man-of-war
SCIENTIFIC NAME:
Physalia physalis
![Helmet shaped beast](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_man_of_war/5940958-2-eng-US/cnidarian_man_of_war_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_man_of_war/5940958-2-eng-US/cnidarian_man_of_war_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_man_of_war/5940958-2-eng-US/cnidarian_man_of_war_full_1468.png 1200w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_man_of_war/5940958-2-eng-US/cnidarian_man_of_war_full_1980.png 1200w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_man_of_war/5940958-2-eng-US/cnidarian_man_of_war_full_2475.png 1200w)
swimming anemone
SCIENTIFIC NAME:
Stomphia coccinea
![Pink anemone with many arms](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_swimming_anemone/5941058-1-eng-US/cnidarians_swimming_anemone_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_swimming_anemone/5941058-1-eng-US/cnidarians_swimming_anemone_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_swimming_anemone/5941058-1-eng-US/cnidarians_swimming_anemone_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_swimming_anemone/5941058-1-eng-US/cnidarians_swimming_anemone_full_1980.png 1980w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_swimming_anemone/5941058-1-eng-US/cnidarians_swimming_anemone_full_2475.png 2400w)
California tube coral
SCIENTIFIC NAME:
Dendrophyllia californica
![Elongated yellow coral](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_california_tube_coral/5940946-1-eng-US/cnidarian_california_tube_coral_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_california_tube_coral/5940946-1-eng-US/cnidarian_california_tube_coral_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_california_tube_coral/5940946-1-eng-US/cnidarian_california_tube_coral_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_california_tube_coral/5940946-1-eng-US/cnidarian_california_tube_coral_full_1980.png 1800w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_california_tube_coral/5940946-1-eng-US/cnidarian_california_tube_coral_full_2475.png 1800w)
smooth flower coral
SCIENTIFIC NAME:
Eusmilia fastigiata
![Irregular shaped yellow coral](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_smooth_flower_coral/5941050-1-eng-US/cnidarians_smooth_flower_coral_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_smooth_flower_coral/5941050-1-eng-US/cnidarians_smooth_flower_coral_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_smooth_flower_coral/5941050-1-eng-US/cnidarians_smooth_flower_coral_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_smooth_flower_coral/5941050-1-eng-US/cnidarians_smooth_flower_coral_full_1980.png 1980w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_smooth_flower_coral/5941050-1-eng-US/cnidarians_smooth_flower_coral_full_2475.png 2000w)
gorgonian coral
SCIENTIFIC NAME:
Gorgonia flabellum
![Yellow fan-shaped coral](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_gorgonian_flabellum/5940954-1-eng-US/cnidarian_gorgonian_flabellum_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_gorgonian_flabellum/5940954-1-eng-US/cnidarian_gorgonian_flabellum_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_gorgonian_flabellum/5940954-1-eng-US/cnidarian_gorgonian_flabellum_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_gorgonian_flabellum/5940954-1-eng-US/cnidarian_gorgonian_flabellum_full_1980.png 1980w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_gorgonian_flabellum/5940954-1-eng-US/cnidarian_gorgonian_flabellum_full_2475.png 2400w)
eggyolk jellyfish
SCIENTIFIC NAME:
Phacellophora camtschatica
![Flowing transparent jelly with yellow core](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_eggyolk_jellyfish/5940950-1-eng-US/cnidarian_eggyolk_jellyfish_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_eggyolk_jellyfish/5940950-1-eng-US/cnidarian_eggyolk_jellyfish_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_eggyolk_jellyfish/5940950-1-eng-US/cnidarian_eggyolk_jellyfish_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_eggyolk_jellyfish/5940950-1-eng-US/cnidarian_eggyolk_jellyfish_full_1980.png 1980w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarian_eggyolk_jellyfish/5940950-1-eng-US/cnidarian_eggyolk_jellyfish_full_2475.png 2400w)
tube anemone
SCIENTIFIC NAME:
Pachycerianthus fimbriatus
![Organism with lots of floating tubes](/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_tube_anemone/5941082-2-eng-US/cnidarians_tube_anemone_full_495.png 495w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_tube_anemone/5941082-2-eng-US/cnidarians_tube_anemone_full_990.png 990w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_tube_anemone/5941082-2-eng-US/cnidarians_tube_anemone_full_1468.png 1468w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_tube_anemone/5941082-2-eng-US/cnidarians_tube_anemone_full_1980.png 1500w,/var/ezflow_site/storage/images/media/amnh/images/explore/ology-images/biodiversity/tree-of-life/cnidarians/cnidarians_tube_anemone/5941082-2-eng-US/cnidarians_tube_anemone_full_2475.png 1500w)
Guess what?
Coral reefs are among the largest structures made by living organisms.
Image Credits:
California tube coral, Gerald and Buff Corsi/© California Academy of Sciences; eggyolk jellyfish, © Tom Thai/CC BY-2.0; gorgonian coral, © Fernando Herranz Martín/GPL; Portuguese man-of-war, Courtesy of Dr. Thomas M. Scott, Florida Geological Survey; smooth flower coral, © Cristian M. Galván Villa/CC BY-NC; swimming anemone, © Sara Thiebaud/CC BY-NC; symmetrical brain coral, © Ali and Brice/CC BY-NC; tube anemone, © Kathleen R./CC BY-NC.