Did You Know? 13 Mushroom Cap Jellyfish Facts

Discover fascinating mushroom cap jellyfish facts about its habitat, physical description, tentacles, and more!

The mushroom cap jellyfish (scientific name Rhopilema verrilli) is a jellyfish species that is a member of the Rhizostomatidae family. They are endemic to the Atlantic coast of America and these jellyfish are cnidarian invertebrates whose mushroom-shaped medusae makes them unique. They do not possess any tentacles, however, they still have stinging cells within their bells, which are known as nematocysts. These nematocysts are capable of stinging humans mildly. These rare jellyfish, Rhopilema verrili, are also known as mushroom cap jellies, jellies, and sea mushroom jellyfish. They're known as mushroom cap jellyfish due to their medusa's shape that is similar to that of the mushroom cap. The Rhopilema verrilli (formerly known as Nectopilema verrilli) was first found in Connecticut's New Haven Harbor and was given its name in 1887 by Fewkes. This jellyfish is now distributed across the western Atlantic of Canada and the U.S.

The mushroom jellyfish is frequently mistaken for the cannonball jellyfish as the bell of each of these organisms do not possess tentacles. However, the mushroom jellyfish has eight finger-shaped oral arms which are absent in the cannonball jellyfish. The mushroom jellyfish species is larger, softer, and flatter too, and can grow up to 20 in (51 cm) in bell diameter. It has a translucent bell that can be of a green, creamy white color or it can be light yellow, brown, blue, or pink. The cannonball jellyfish species has a rougher umbrella and it is rounder. It also has brownish edges that grow up to 10 in (25 cm) in diameter. Keep reading to learn more about this fascinating jelly and discover facts about its habitat, sting, stinging cells, and more!

If you enjoyed reading our mushroom jellyfish interesting facts, you must check out our fried egg jellyfish facts for kids and moon jelly surprising facts!

Mushroom Cap Jellyfish

Fact File

What do they prey on?

Tiny plankton parts

What do they eat?


Average litter size?

1 egg

How much do they weigh?


How long are they?

Bell diameter: 20 in (51 cm)

How tall are they?


What do they look like?

White, brown, light brown, light yellow, blue, pink or green

Skin Type


What are their main threats?


What is their conservation status?

Not Evaluated

Where you'll find them

Inshore in the mouths of estuaries


Western Atlantic of the U.S. and Canada, along the coast of the northern Gulf of Mexico, and between North Carolina and New England





Scientific Name

Rhopilema verrilli





Mushroom Cap Jellyfish Interesting Facts

What type of animal is a mushroom cap jellyfish?

The mushroom jellyfish, Rhopilema verrilli,  is a jellyfish species. Its diet comprises small plankton parts that this jelly catches with its finger-like appendages.  It has a translucent bell that can be of a green, creamy white, light yellow, brown, blue, or pink color. The bell does not possess tentacles. Under their bell, there are eight oral arms that also possess finger-like appendages that have brownish tints at the ends. Sideways, it has reddish-brown-colored pigmentation from its organs.

What class of animal does a mushroom cap jellyfish belong to?

The mushroom jellyfish, Rhopilema verrilli, belongs to the class Scyphozoa.

How many mushroom cap jellyfish are there in the world?

The population of this mushroom jellyfish is not known yet as this species has not been evaluated by the IUCN. However, it is considered to be a rare species.

Where does a mushroom cap jellyfish live?

The mushroom jellyfish, Rhopilema verrilli, ranges across the U.S. and Canada's western Atlantic and also the northern Gulf of Mexico's coast, as well as between New England and North Carolina. During early winter and fall, they also occur in lower Chesapeake Bay.

What is a mushroom cap jellyfish's habitat?

The typical mushroom cap jellyfish habitat comprises mainly gulf, or sometimes inshore areas around the mouth of a bay. It has been observed in abundance along the Gulf of Mexico's coast, in North Carolina, Chesapeake Bay, and New England.

Who do mushroom cap jellyfish live with?

It is not known with whom this jellyfish lives within its habitat. However, it has been spotted with one to two jellyfish of the same species in waters surrounding the mouth of a bay.

How long does a mushroom cap jellyfish live?

The lifespan of the sea mushroom jellyfish has not been evaluated. However, numerous jellyfish species have a life span of one year and one is even immortal, which is the immortal jellyfish!

How do they reproduce?

These cnidarians alternate between sexual medusa and asexual polyps. They only have one life, but they transition through different forms within their lifetime. Scyphozoan jellyfishes live as a medusa for the maximum part of their life cycles. The adult medusa lays an egg which, after fertilization, develops into a planula, or a free-living larva. This planula will then float around until it attaches itself to a hard surface like an oyster shell. Then it undergoes metamorphosis, becoming a scyphistoma, which is a polyp. This scyphistoma reproduces asexually via budding and transforms itself into a strobila. Every strobila will mature into an ephryae which are a medusa's immature form. After maturing, it breaks from the strobila and this ephryae becomes an adult medusa finally.

What is their conservation status?

The mushroom jellyfish has not yet been assessed by the IUCN. Hence, it is Not Evaluated.

Mushroom Cap Jellyfish Fun Facts

What do mushroom cap jellyfish look like?

Mushroom jellyfish have unique medusae that are mushroom-shaped. They do not possess any tentacles, but they still have stinging cells, which are known as nematocysts. These are present within their bells and have the ability to produce stings (mild) on humans. The bell diameter typically ranges between 13.7-19.6 in (35-50 cm) but the maximum bell diameter can be 20 in (51 cm). Its bell is mushroom-shaped, translucent, and gelatinous. The color of the bell can range between pink, green, white, light yellow, brown, and blue. The bell margins have a light-brown-colored pigmentation usually. Sideways, it has reddish-brown-colored pigmentation from its organs that are located below, such as the digestive glands that are pinkish in color. Instead of tentacles, this species has eight oral arms that have finger-shaped appendages along with nematocyst warts present below the umbrella's center. Its eight oral arms have a brown coloration and this species has eight rhopalia that are pink-colored small structures present near the margin of the bell. This jelly has eight radial canals that make up the gastroendodermal system along with the stomach. Its mouth and underside can be seen from underneath.

Mushroom cap jellyfish have no tentacles and a translucent bell!

How cute are they?

The mushroom jellyfish is quite cute. It possesses a translucent bell that can be pink, green, white, light yellow, brown, or blue in color.

How do they communicate?

This jellyfish has no tentacles. However, its rhopalium comprises a gravity sensor that allows this creature to sense its direction and orientation.

How big is a mushroom cap jellyfish?

The mushroom jellyfish, Rhopilema verrilli, ranges between 13.7-19.6 in (35-50 cm) but the maximum bell diameter of this jelly can be 20 in (51 cm).

How fast can a mushroom cap jellyfish swim?

The speed of the sea mushroom jellyfish has not been evaluated yet. But we do know that jellyfish species can be efficient at swimming and many jellyfish can be found swimming at the rate of 47 in/m (2 cm/s).

How much does a mushroom cap jellyfish weigh?

The weight of the sea mushroom jellyfish is not known yet. However, we do know that the weight of the largest jellyfish ranges between 330.7-440.9 lb (150-200 kg)!

What are their male and female names of the species?

Male and female jellyfish do not have particular names.

What would you call a baby mushroom cap jellyfish?

A baby sea mushroom jellyfish is referred to as ephyrae.

What do they eat?

This mushroom jellyfish consumes small plankton parts which they push out with their umbrella through water and then catch with finger-like appendages. Jellyfish are generally consumed by sea anemones, swordfish, sharks, tunas, penguins, and sea turtles.

Are they poisonous?

No, these creatures aren't poisonous. They can cause a mild sting to a human though.

Would they make a good pet?

They are considered pests by commercial fishermen. Although they are quite harmless and can be kept as a pet, they are quite unpopular in the pet trade due to the size they can reach.

Did you know...

Mushroom cap jellyfish are eaten by humans. They are dried out in a paste or served pickled in Japan and China!

Do mushroom cap jellyfish sting?

These jellies do not possess stinging tentacles, however, they still have stinging cells that can deliver mild, but painful, stings to humans within their bells. The sting of this marine creature causes only mild irritation. However, swimmers must avoid them as a serious sting can cause a lot of pain.

What is the friendliest jellyfish?

The moon jellyfish is the friendliest jellyfish of all. This species can be spotted in Europe's eastern Atlantic coast and North America's western Atlantic coast. They are also spotted on Canada's coasts.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other Scyphozoans from our barrel jellyfish interesting facts and Irukandji jellyfish surprising facts pages!

You can even occupy yourself at home by coloring in one of our free printable jellyfish coloring pages!



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