Cnidarians | Cnidaria

Cnidarians or Cnidaria are mostly found in marine environments. However, some species are found in freshwater bodies. They include sea anemones, corals, and jellyfish. They are identified by the cnidocyte cells for capturing prey. Their body is sandwiched between two epithelium cells and composed of a living jelly-like substance called mesoglea. Cnidarians mainly prey on planktons, parasites, and small animals like turtles and sea slugs. Adult cnidarians have no heads and would appear as free-swimming medusae or sessile polyps. They have tentacles around their edges and inner mouths and reproduce either sexually or asexually.

What do cnidarians use for defense?

Cnidarians are aquatic animals with two body forms (the ectoderm and endoderm separated by a mesoglea). To capture prey or even defend themselves, cnidarians have unique and well-developed specialized cells in their mouths and tentacles for stinging attackers. These cells, called cnidocytes, have toxins that are released when their body is touched.

How do cnidarians reproduce?

Sexual and asexual reproduction are the forms of reproduction seen among cnidarians. Besides, some are hermaphrodites — capable of producing both eggs and sperms at the same time. However, asexual reproduction is the most common in this species. Sexual reproduction may occur only in one phase of a cnidarian’s life cycle.

Do cnidarians have brains?

What cnidarians have are diffuse nets of nerves that coordinate messages around their bodies. Research shows that these nets of nerves are just as complex as that of human beings. In addition, some like jellyfish, have no heart or eyes. Most cnidarians also have a transparent body covered in a chitinous exoskeleton.

Cnidarians Guides
Browse through our curated Cnidarians Guides for additional categorizations, tips, details, variations, styles, and histories of Cnidarians. Guides provide additional insights into the unique properties and shared relationships between elements.
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2.36”-4.33” | 6-11 cm
5”-9.84” | 12.7-25 cm
17.7”-35” | 45-89 cm
6-18 months
Atlantic Sea Nettle
11.000
25.000
89.000
1.50
300
GUIDE
3D
Atlantic Sea Nettle
.79”-6.7” | 2-17 cm
.79”-6.7” | 2-17 cm
1.6”-13.8” | 4-35 cm
Atolla Jellyfish
17.000
17.000
35.000
1200
GUIDE
3D
Atolla Jellyfish
12.6”-47” | 32-119 cm
15.75”-59” | 40-150 cm
29”-108” | 74-274 cm
55-88 lb | 25-40 kg
2-6 months
Barrel Jellyfish
119.000
150.000
274.000
40.000
0.50
6400
GUIDE
3D
Barrel Jellyfish
8.3”-18.9” | 21-48 cm
16”-36” | 40.6-91.4 cm
44”-104” | 112-264 cm
6-12 months
Black Sea Nettle Jellyfish
48.000
91.400
264.000
1.00
350
GUIDE
3D
Black Sea Nettle Jellyfish
.59”-6.3” | 1.5-16 cm
.47”-3.94” | 1.2-10 cm
.59”-6.3” | 1.5-16 cm
Bloodybelly Comb Jellyfish
16.000
10.000
16.000
100
GUIDE
3D
Bloodybelly Comb Jellyfish
27.6”-35.4” | 70-90 cm
31.5”-39.4” | 80-100 cm (Diameter)
31.5”-39.4” | 80-100 cm (Diameter)
Blue Coral
90.000
100.000
100.000
17400
GUIDE
3D
Blue Coral
7.1”-13.8” | 18-35 cm
9.84”-17.72” | 25-45 cm
24.8”-44.9” | 63-114 cm
1 year
Blue Jellyfish
35.000
45.000
114.000
1.00
5800
GUIDE
3D
Blue Jellyfish
9.8”-19.7” | 25-50 cm
11.8”-23.6” | 30-60 cm (Diameter)
11.8”-23.6” | 30-60 cm (Diameter)
Bubble Coral
50.000
60.000
60.000
5300
GUIDE
3D
Bubble Coral
5.5”-7.9” | 14-20 cm
7.1”-9.84” | 18-25 cm
7.5”-10.6” | 19-27 cm
.31-3 lb | .14-1.38 kg
3-6 months
Cannonball Jellyfish
20.000
25.000
27.000
1.380
0.50
12000
GUIDE
3D
Cannonball Jellyfish
3.5”-6.3” | 9-16 cm
5.9”-10” | 15-25.4 cm
16.5”-27.2” | 42-69 cm
.44-5.3 lb | .2-2.4 kg
1 year
Compass Jellyfish
16.000
25.400
69.000
2.400
1.00
5600
GUIDE
3D
Compass Jellyfish
8.7”-19.7” | 22-50 cm
9.84”-23.62” | 25-60 cm
13”-30.7” | 33-78 cm
.04-.89 lb | .02-.4 kg
3-6 months
Crowned Jellyfish
50.000
60.000
78.000
0.400
0.50
5
GUIDE
3D
Crowned Jellyfish
.5”-5.9” | 1.2-15 cm
.8”-10” | 2-25.4 cm
1.2”-14.2” | 3-36 cm
2-6 months
Crystal Jellyfish
15.000
25.400
36.000
0.50
1500
GUIDE
3D
Crystal Jellyfish
.3”-.63” | .8-1.6 cm
.39”-.79” | 1-2 cm
.67”-1.34” | 1.7-3.4 cm
Darth Vader Jellyfish
1.600
2.000
3.400
40
GUIDE
3D
Darth Vader Jellyfish
4’-8’ | 1.22-2.43 m
11.5’-13’ | 3.5-3.96 m (Diameter)
11.5’-13’ | 3.5-3.96 m (Diameter)
Elkhorn Coral
243.000
396.000
396.000
1450
GUIDE
3D
Elkhorn Coral
5.1”-6.3” | 13-16 cm
5.9”-7.9” | 15-20 cm (Diameter)
5.9”-7.9” | 15-20 cm (Diameter)
Finger Coral
16.000
20.000
20.000
1340
GUIDE
3D
Finger Coral
4.7”-5.9” | 12-15 cm
4.72”-5.91” | 12-15 cm
8.3”-10.6” | 21-27 cm
4-6 months
Flower Hat Jelly
15.000
15.000
27.000
0.50
150
GUIDE
3D
Flower Hat Jelly
1.6”-8.7” | 4-22 cm
2.36”-11.8” | 6-30 cm
2”-10.2” | 5-26 cm
4-6 months
Fried Egg Jellyfish
22.000
30.000
26.000
0.50
2000
GUIDE
3D
Fried Egg Jellyfish
10.2”-41.3” | 26-105 cm
15.75”-78.75” | 40-200 cm
28.3”-143” | 72-362 cm
200-480 lb | 91-217 kg
1 year
Lion’s Mane Jellyfish
105.000
200.000
362.000
217.000
1.00
6900
GUIDE
3D
Lion’s Mane Jellyfish
.79”-2.75” | 2-7 cm
1.18”-3.94” | 3-10 cm
3.15”-11” | 8-28 cm
6-9 months
Mauve Stinger
7.000
10.000
28.000
0.75
2300
GUIDE
3D
Mauve Stinger
3.94”-9.1” | 10-23 cm
5.91”-13.78” | 15-35 cm
7.1”-16.5” | 18-42 cm
.01-.07 lb | .01-.03 kg
8-12 months
Moon Jellyfish
23.000
35.000
42.000
0.030
1.00
56000
GUIDE
3D
Moon Jellyfish
7.9”-11.8” | 20-30 cm
11.8”-19.7” | 30-50 cm (Diameter)
11.8”-19.7” | 30-50 cm (Diameter)
Organ Pipe Coral
30.000
50.000
50.000
2400
GUIDE
3D
Organ Pipe Coral
22”-27.2” | 56-69 cm
30”-36” | 76.2-91.4 cm
55”-67” | 140-170 cm
30-50 lb | 14-23 kg
Pink Meanie Jellyfish
69.000
91.400
170.000
23.000
1200
GUIDE
3D
Pink Meanie Jellyfish
2”-5.1” | 5-13 cm
4.72”-11.8” | 12-30 cm
8.7”-23.2” | 22-59 cm
1 year
Portuguese Man o' War
13.000
30.000
59.000
1.00
17000
GUIDE
3D
Portuguese Man o' War
3.5”-5.1” | 9-13 cm
2.95”-3.94” | 7.5-10 cm
6.7”-9.1” | 17-23 cm
Red Paper Lantern Jellyfish
13.000
10.000
23.000
5
GUIDE
3D
Red Paper Lantern Jellyfish
3’-5’ | .91-1.52 m
3.3’- 9.8’ | 1-3 m (Diameter)
3.3’- 9.8’ | 1-3 m (Diameter)
Staghorn Coral
152.000
300.000
300.000
2500
GUIDE
3D
Staghorn Coral
13.4”-14.2” | 34-36 cm
17.7”-19.7” | 45-50 cm
36.2”-41.7” | 92-106 cm
20-24 lb | 9-11 kg
1 year
White-Spotted Jellyfish
36.000
50.000
106.000
11.000
1.00
410
GUIDE
3D
White-Spotted Jellyfish
Crowned Jellyfish (Cephea cephea)
Measured comparison illustration of the size of a Crowned Jellyfish to a typical person and jellyfish

The Crowned jellyfish, known as Cephea cephea, is a crown jellyfish usually found in the cold water up to 3,000 feet below the surface in the Indo-Pacific ocean. The Crowned jellyfish is purple and blue in color, bioluminescent, and has the distinctive bell shape of crown jellies. The Crown jellyfish also has warts that protrude off its body. The Crowned jellyfish is one of the most venomous jellyfish, yet not to humans; therefore, it is eaten as a delicacy and even used medically in certain Asian countries. The Crowned jellyfish, like most other jellies, has tentacles that can be used to stun and capture its prey.

Crowned Jellyfish have a bell width between 9.84”-23.62” (25-60 cm), bell height of 8.7”-19.7” (22-50 cm), and overall length of 13”-30.7” (33-78 cm). The typical lifespan of the Crowned Jellyfish is 3-6 months with a weight between .04-.89 lb (.02-.4 kg).

Scaled collection of drawings of Crowned Jellyfish in front and side poses
The Crowned jellyfish, known as Cephea cephea, is a crown jellyfish usually found in the cold water up to 3,000 feet below the surface in the Indo-Pacific ocean. The Crowned jellyfish is purple and blue in color, bioluminescent, and has the distinctive bell shape of crown jellies.

Crowned Jellyfish have a bell width between 9.84”-23.62” (25-60 cm), bell height of 8.7”-19.7” (22-50 cm), and overall length of 13”-30.7” (33-78 cm). The typical lifespan of the Crowned Jellyfish is 3-6 months with a weight between .04-.89 lb (.02-.4 kg).

Scaled collection of drawings of Crowned Jellyfish in front and side poses
Crowned Jellyfish (Cephea cephea)
Height:
8.7”-19.7” | 22-50 cm
Width:
9.84”-23.62” | 25-60 cm
Length:
13”-30.7” | 33-78 cm
Depth:
Weight:
.04-.89 lb | .02-.4 kg
Area:
Scientific Name
Cephea cephea
Lifespan
3-6 months

Drawings include:

Crowned Jellyfish side elevation, front, top

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Organ Pipe Coral (Tubipora musica)
Scale illustration of an average Organ Pipe Coral compared to other coral species and a person

The Organ Pipe Coral (Tubipora musica) is one coral that you can see both in the sea and in the aquarium. Aquarium owners love it because of its ease of maintenance and non-stinging nature. In the wild, you will find it in the water of the Indian Ocean and also in central and western Pacific regions. These areas must be shallow and sheltered with good light conditions. It is considered a soft coral, though the bright red skeleton is hard calcium carbonate with many organic pipe-like tubes. Each tube has polyps with eight feather-like tentacles.

The Organ Pipe Coral has an overall colony diameter between 11.8”-19.7” (30-50 cm) and typical height of 7.9”-11.8” (20-30 cm).

Series of top and side view illustrations of the Organ Pipe Coral
The Organ Pipe Coral (Tubipora musica) is one coral that you can see both in the sea and in the aquarium. Aquarium owners love it because of its ease of maintenance and non-stinging nature. In the wild, you will find it in the water of the Indian Ocean and also in central and west Pacific regions.

The Organ Pipe Coral has an overall colony diameter between 11.8”-19.7” (30-50 cm) and typical height of 7.9”-11.8” (20-30 cm).

Series of top and side view illustrations of the Organ Pipe Coral
Organ Pipe Coral (Tubipora musica)
Height:
7.9”-11.8” | 20-30 cm
Width:
11.8”-19.7” | 30-50 cm (Diameter)
Length:
Depth:
11.8”-19.7” | 30-50 cm (Diameter)
Weight:
Area:
Scientific Name
Tubipora musica
Lifespan

Drawings include:

Organ Pipe Coral top view, side (assorted)

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Flower Hat Jelly (Olindias formosus)
Scale illustration of an average Flower Hat Jelly with dimensions length compared to other jellyfish

The Flower Hat jelly, known scientifically as Olindias formosus, is a rare, multi-colored jelly that is not a true jellyfish, but rather a hydrozoa, which is a small predator that lives in colony with specialized roles between the individual organisms. The Flower Hat jelly can be found off the coasts of Japan, South Korea, Argentina, and Brazil. The Flower Hat jelly is distinctive with its translucent, pin-striped hat and coiled tentacles that drape off the edge of the cap. The Flower Hat jelly spends time both on the bottom of the sea floor and floating to hunt for prey. The Flower Hat jelly has a painful sting, usually resulting in a rash, but one death from the Flower Hat has been recorded.

Flower Hat Jellies have a bell width between 4.72”-5.91” (12-15 cm), bell height of 4.7”-5.9” (12-15 cm), and overall length of 8.3”-10.6” (21-27 cm). The typical lifespan of the Flower Hat Jelly is 4-6 months.

Pair of elevation illustrations of the Flower Hat Jelly seen from the side and front
The Flower Hat jelly, known scientifically as Olindias formosus, is a rare, multi-colored jelly that is not a true jellyfish, but rather a hydrozoa, which is a small predator that lives in colony with specialized roles between the individual organisms.

Flower Hat Jellies have a bell width between 4.72”-5.91” (12-15 cm), bell height of 4.7”-5.9” (12-15 cm), and overall length of 8.3”-10.6” (21-27 cm). The typical lifespan of the Flower Hat Jelly is 4-6 months.

Pair of elevation illustrations of the Flower Hat Jelly seen from the side and front
Flower Hat Jelly (Olindias formosus)
Height:
4.7”-5.9” | 12-15 cm
Width:
4.72”-5.91” | 12-15 cm
Length:
8.3”-10.6” | 21-27 cm
Depth:
Weight:
Area:
Scientific Name
Olindias formosus
Lifespan
4-6 months

Drawings include:

Flower Hat Jelly side elevation, front, top

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Portuguese Man o' War (Physalia physalis)
Dimensioned comparison drawing of the Portuguese Man o' War compared to other jellyfish and a person

The Portuguese Man O’ War, known scientifically as Physalia physalis, is often mistaken for a jellyfish, when in reality it is a siphonophore, a colonial organism made up of multiple smaller zooids. The Portuguese Man O’ War is considered to be the same species as the Pacific Man O’ War. The Portuguese Man O’ War consists of its top, called a pneumatophore, which is mainly translucent blue with hints of purple, that is filled with carbon monoxide and acts as a sail and flotation device for the organism. Dangling from its top are the Portuguese Man O’War’s killer tentacle zooids which kill fish, and have even killed humans, as it floats along the top of the ocean surface. The Portuguese Man O’ War lives solely on the ocean’s surface making it a member of the neuston, a highly complex ecology of ocean surface dwelling creatures, of which little is known.

Portuguese Man o' Wars have a bell width between 4.72”-11.8” (12-30 cm), bell height of 2”-5.1” (5-13 cm), and overall length of 8.7”-23.2” (22-59 cm). The typical lifespan of the Portuguese Man o' War is 1 year.

Set of scaled elevation drawings of the Portuguese Man o' War viewed from the front and side
The Portuguese Man O’ War, known scientifically as Physalia physalis, is often mistaken for a jellyfish, when in reality it is a siphonophore, a colonial organism made up of multiple smaller zooids. The Portuguese Man O’ War is considered to be the same species as the Pacific Man O’ War.

Portuguese Man o' Wars have a bell width between 4.72”-11.8” (12-30 cm), bell height of 2”-5.1” (5-13 cm), and overall length of 8.7”-23.2” (22-59 cm). The typical lifespan of the Portuguese Man o' War is 1 year.

Set of scaled elevation drawings of the Portuguese Man o' War viewed from the front and side
Portuguese Man o' War (Physalia physalis)
Height:
2”-5.1” | 5-13 cm
Width:
4.72”-11.8” | 12-30 cm
Length:
8.7”-23.2” | 22-59 cm
Depth:
Weight:
Area:
Scientific Name
Physalia physalis
Lifespan
1 year

Drawings include:

Portuguese Man o' War side elevation, front, top

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Compass Jellyfish (Chrysaora hysoscella)
Scale illustration of an average Compass Jellyfish with dimensions length compared to a human and jellyfish

The Compass jellyfish, known scientifically as Chrysaora hysoscella, is a yellow-white jellyfish with brown markings on the top of its bell. These markings are v-shaped and radiant out from the center and resemble a compass, the Compass jellyfish’s namesake. Along the edge of the bell, the Compass jellyfish protrudes fringe with wavy oral arms and has tentacles hanging from the center of the bell. The Compass jelly has a powerful sting and should be avoided if recognized on the beach. The Compass jelly is common off the coast of Britain during the warmer summer months.

Compass Jellyfish have a bell width between 5.9”-10” (15-25.4 cm), bell height of 3.5”-6.3” (9-16 cm), and overall length of 16.5”-27.2” (42-69 cm). The typical lifespan of the Compass Jellyfish is 1 year with a weight between .44-5.3 lb (.2-2.4 kg).

Pair of elevation illustrations of the Compass Jellyfish seen from the side and front
The Compass jellyfish, known scientifically as Chrysaora hysoscella, is a yellow-white jellyfish with brown markings on the top of its bell. These markings are v-shaped and radiant out from the center and resemble a compass, the Compass jellyfish’s namesake.

Compass Jellyfish have a bell width between 5.9”-10” (15-25.4 cm), bell height of 3.5”-6.3” (9-16 cm), and overall length of 16.5”-27.2” (42-69 cm). The typical lifespan of the Compass Jellyfish is 1 year with a weight between .44-5.3 lb (.2-2.4 kg).

Pair of elevation illustrations of the Compass Jellyfish seen from the side and front
Compass Jellyfish (Chrysaora hysoscella)
Height:
3.5”-6.3” | 9-16 cm
Width:
5.9”-10” | 15-25.4 cm
Length:
16.5”-27.2” | 42-69 cm
Depth:
Weight:
.44-5.3 lb | .2-2.4 kg
Area:
Scientific Name
Chrysaora hysoscella
Lifespan
1 year

Drawings include:

Compass Jellyfish side elevation, front, top

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