About Rhopilema verrilli (Fewkes, 1887)
Rhopilema verrilli, commonly called the mushroom jellyfish, has a bell diameter ranging from 35 to 50 cm, with a recorded maximum bell diameter of 51 cm. Its bell is gelatinous, mushroom-shaped, and translucent, and can be any of a range of colors including white, light yellow, brown, blue, pink, or green. Bell margins usually have very light-brown pigmentation, while the lateral body surface has reddish-brown pigmentation from underlying organs such as the pinkish digestive glands. Unlike many jellyfish, this species lacks tentacles. Instead, it has 8 oral arms that bear finger-shaped appendages, with nematocyst warts located under the middle of the umbrella; the oral arms are brownish in color. Rhopilema verrilli has 8 small pink sensory structures called rhopalia arranged around the bell margin; each rhopalium holds a gravity sensor that lets the jellyfish detect its orientation and direction. It also has 8 radial canals, which together with the stomach make up the gastroendodermal system. This species is distributed across the western Atlantic off the United States and Canada, and is most common along coasts in the northern Gulf of Mexico, and between North Carolina and New England. It sometimes occurs inshore in estuary mouths, and may enter the lower Chesapeake Bay during fall and early winter. Its documented range spans from 18.21° to 38.32° latitude, and from -97.8° to -76.5° longitude. As a scyphozoan cnidarian, Rhopilema verrilli spends most of its life cycle in the medusa form, and it is gonochoric (unisexual). Its life cycle begins when an adult medusa lays an egg. After fertilization, the egg develops into a free-swimming planula larva. The planula floats until it attaches to a hard substrate, where it metamorphoses into a polyp called a scyphistoma. The scyphistoma reproduces asexually via budding, then develops into a strobila. Each segment of the strobila matures into an ephyra, an immature medusa. Once ephyrae mature and detach from the strobila, they become adult medusae.
