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

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

in the family Rhizostomatidae. They are

cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in Fresh water, freshwater and Marine habitats, marine environments, predominantly the latter. Their distinguishing feature is cnidocyt ...

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s distinguished by their mushroom-shaped medusae. The species does not have any tentacles; however, they still have stinging cells, called nematocysts, 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 fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is ...

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

. 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 ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United S ...

, and between

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia a ...

and

New England New England is a region comprising 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 to the west and by the Canadian province ...

. 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 environme ...

. 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 the parts: the ...

. 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 animals found both in Fresh water, freshwater and Marine habitats, marine environments, predominantly the latter. Their distinguishing feature is cnidocyt ...

ns have life cycles that alternate between asexual polyps and sexual

medusa In Greek mythology, Medusa (; Ancient Greek: Μέδουσα "guardian, protectress"), also called Gorgo, was one of the three monstrous Gorgons, generally described as winged human females with living venomous snakes in place of hair. Those ...

. 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 only 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 ...

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. Some groups of Nemerteans also produce larvae that are very similar to the planula, whi ...

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

References

{{Taxonbar, from=Q2148279 Rhizostomatidae Animals described in 1887