Jellyfish

Jellyfish are floating, gelatinous animals with a familiar umbrella-shaped bell, called a medusa. Tentacles with stinging cells called nematocysts hang from the bell.

What species of jellyfish live in the Bay?

Three species of jellyfish can be found in the Bay:

• The sea nettle, Chrysaora quinquecirrha, is the most well-known of the Bay jellyfish. Its smooth, milky white bell usually grows to about 4 inches in diameter. Up to 24 stinging tentacles emerge from marginal clefts inside of the bell.
• The moon jellyfish, Aurelia aurita, is the largest jellyfish found in the Bay, growing to about 10 to 12 inches in diameter. It has a flat, white bell with four pink horseshoe-shaped gonads in the center. Hundreds of short tentacles hang like fringe from the edge of the bell.
• The winter jellyfish or lion's mane jellyfish, Cyanea capillata, has a broad, flattish bell with eight clusters of short tentacles. The bell is usually orange-brown and about the same size as the sea nettle's.

Where do jellyfish live?

Jellyfish are found throughout the year in the middle and lower Bay and nearby rivers. Jellyfish can propel themselves forward by rhythmically expanding and contracting their bells. However, they are not strong swimmers; rather, they are widely transported by winds and currents.

• Sea nettles are abundant from May through October as far north as Sandy Point State Park in Annapolis, Maryland.
• Moon jellyfish are found in the middle and lower Bay around the same time of year as sea nettles.
• Winter jellyfish are found in the Bay from late November through the end of May. They enter as young (called ephyrae) and mature throughout the winter.

Watch this video to see a Bay jellyfish move by expanding and contracting its bell:

What do jellyfish eat?

Jellyfish use their stinging tentacles to entangle, paralyze and capture their prey, which includes fish, shrimp, comb jellies and other small creatures.

• Each nematocyst is like a barb, injecting venom into any creature that brushes against the jellyfish's tentacles.
• The captured prey is then passed into the jellyfish's mouth, which is located under the center of the bell.

How do jellyfish reproduce?

In the Bay, sea nettles spawn in mid-summer after growing and maturing through the spring. They die after spawning.

• Jellyfish spawn when males release sperm into the water. Females' eggs are fertilized internally as they swim and pump water through the body.
• After fertilization, eggs develop into tiny, ciliated, free-swimming larvae called planulae, which are released into the water and float with the currents.
• Planulae settle after a few days and attach to firm surfaces, such as rocks, pilings, debris and oyster shells.
• Once attached, planulae blossom into anemone-like polyps that bud and grow over the winter.
• By spring, polys develop into larger forms with tiny, floating medusae layered on top of one another.
• The medusae are eventually released into the water. The freely floating medusae, called ephyra, eventually develop tentacles and mature into adult jellyfish.

Winter jellyfish young, or ephyra, enter the Bay in late fall and grow throughout the winter. They leave the Bay in late spring as adults.

Other facts about jellyfish:

• Jellyfish are macrozooplankton, the largest of the planktonic animals in the Bay.
• Sea nettles are almost 90 percent water, yet many larger species — including fish, invertebrates and sea turtles — feed on them.
• Several fishes have developed symbiotic relationships with sea nettles. Young harvestfish and butterfish can swim within the sea nettle's tentacles without being stung.
• Wearing a wet suit or pantyhose can protect swimmers and boaters from a jellyfish's sting.
• The sting of a sea nettle can be counteracted by putting vinegar on the affected area.