''Rhopilema verrilli'', the mushroom cap jellyfish, is a species of

jellyfish Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...

in the family

Rhizostomatidae Rhizostomatidae is a family of cnidarians in the class Scyphozoa. Genera and species According to the World Register of Marine Species, 11 extant species are in four extant genera within this family: *Genus ''Eupilema'' **'' Eupilema inexpectat ...

. They are

cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s distinguished by their mushroom-shaped medusae. The species does not have any tentacles; however, they still have stinging cells, called

nematocysts A cnidocyte (also known as a cnidoblast) is a type of cell containing a large secretory organelle called a ''cnidocyst'', that can deliver a sting to other organisms as a way to capture prey and defend against predators. A cnidocyte explosively ...

, within their bells, which can produce mild stings to humans.

Taxonomy

"Mushroom cap jellyfish" and "sea mushroom jellyfish" are common names for the rare ''Rhopilema verrili''. Their common name refers to the shape of the medusa, which resembles a

mushroom A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the n ...

cap. ''Rhopilema verrilli,'' originally ''Nectopilema verrilli'', was named by Fewkes (1887) after a specimen found in the

New Haven Harbor New Haven Harbor is an inlet on the north side of Long Island Sound in the state of Connecticut. Centered on the city of New Haven, the state's third largest, it was carved by the retreat of the glaciers during the last ice age approximately 13, ...

of Connecticut. The mushroom jellyfish is often confused with the

cannonball jellyfish The cannonball jellyfish (''Stomolophus meleagris''), also known as the cabbagehead jellyfish, is a species of jellyfish in the family Stomolophidae. Its common name derives from its similarity to a cannonball in shape and size. Its dome-shaped ...

. Both species lack tentacles, but the ''R. verrilli'' has finger-shaped arms, while the ''S. meleagris'' does not. The mushroom jellyfish is also much flatter, softer, and larger as it can be up to 51 cm or 20 inches in diameter. Conversely, the cannonball jellyfish is more roundish and has a slightly rougher umbrella that is brownish on the edge and grows up to 25 cm or 10 inches in diameter.

Description

The diameter of ''Rhopilema verrilli'' ranges from 35 to 50 cm; the maximum size found is 51 cm in bell diameter. The bell is gelatinous, mushroom-shaped, and translucent. The bell ranges from a variety of colors such as white to light yellow, brown, blue, pink or green. The margins of the bell usually have a very light-brown pigmentation. Laterally, the species has a reddish-brown pigmentation from the organs underneath such as the pinkish digestive glands. The mushroom jellyfish lack tentacles; instead, they have 8 oral arms with finger-shaped appendages with nematocyst warts underneath the middle of the umbrella. The arms are brownish in color. The species has 8 rhopalia, which are small pink structures located around the bell margin. Each rhopalium contains a gravity sensor, allowing the jellyfish to tell its orientation and direction. This jellyfish also has 8 radial canals. The radial canals along with the stomach form the gastroendodermal system.

Distribution and habitat

''Rhopilema verrilli'' are distributed throughout the Western Atlantic of the U.S. and Canada, but they reside mostly along the coast in the northern

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

, and between

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

and

New England New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...

. They sometimes occur inshore in mouths of

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

. During the fall and early winter, they may enter into the lower

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula, including parts of the Ea ...

. The species are distributed along the latitude coordinates: 18.21 degrees (min) and 38.32 degrees (max) and longitude coordinates: -97.8 degrees (min) and -76.5 degrees (max).

Behavior

The mushroom jellyfish survive off of tiny plankton parts, which are pushed out of their umbrella by the water and are caught with their finger-like appendages. ''R. verrilli'' do not present a stinging threat to humans because they do not have tentacles but stinging cells that reside inside their bells.

Life cycle

Cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

ns have life cycles that alternate between asexual polyps and sexual

medusa In Greek mythology, Medusa (; ), also called Gorgo () or the Gorgon, was one of the three Gorgons. Medusa is generally described as a woman with living snakes in place of hair; her appearance was so hideous that anyone who looked upon her wa ...

. However, the class

Scyphozoa The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish (or "true jellies"). The class name Scyphozoa comes from the Greek word '' skyphos'' (), denoting a kind of drinking cup and alluding to the ...

n jellyfishes live most of their life cycles as a medusa. ''R. verrilli'', belonging to the class

, are

gonochoric In biology, gonochorism is a sexual system where there are two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism contrast ...

or unisexual. The life cycle starts off by the adult medusa laying an egg. After fertilization, the egg develops into a free-living larva, or

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores, which are not related to cnidarians at all. Some groups of Nemerteans also produce larva ...

. The planula floats around until it attaches itself onto a hard substrate, metamorphosing itself into a polyp called, scyphistoma. The scyphistoma will reproduce asexually through budding, and transform into a strobila. Each stroblia matures into an ephryae, an immature form of a medusa. When they mature and break away from the other stroblia, the ephryae finally becomes an adult medusa.

Human interactions

Commercial fishermen consider ''R. verrilli'' and ''S.'' ''meleagris'' as pests, but ''R. verrilli'' are less of a problem than ''S.'' ''meleagris''. The mushroom jellyfishes are served pickled, or dried out into paste in Asian countries such as

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

and

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. The taxon for ''Rhopilema'' has not yet been assessed for the IUCN Red List.

References

{{Taxonbar, from=Q2148279 Rhizostomatidae Cnidarians of the Atlantic Ocean Animals described in 1887