It has long tentacles and a potent sting. While it is not dangerous to swimmers, it is very unpleasant to encounter. Deborah Steinberg June 1, I want to avoid jellyfish while swimming in Chesapeake Bay. What steps can I take? For the last years, scientists have assumed these two common jellyfish were a single species. His curiosity piqued, he decided to take some samples back to the Natural History Museum. Genetic testing revealed these animals were quite different than those found in the nearby Chesapeake Bay and Rehoboth Bay.
The bay-based species is found in the less salty waters known as estuaries, such as the Chesapeake Bay, and is the newly recognized species of the two. Both jellyfish were previously classified as Chrysaora quinquecirrha. They use their stinging tentacles to entangle, paralyze and capture their prey.
Each stinging cell is like a barb that injects venom into its prey. Jellyfish then use their tentacles to move the food into their mouth, which is located under the center of the bell. Moon jellyfish eat plankton, including mollusks, crustaceans and copepods. Sea nettles spawn in mid-summer.
They die after spawning. Males release sperm into the water. After fertilization, eggs develop into tiny, free-swimming larvae called planulae, which the female releases into the water. Larvae float with the currents for a few days, then settle and attach to a firm surface.
The non-stinging comb jellies are actually a distant cousin to the jellyfish. Their walnutshaped forms reach a maximum size of about five inches and can glow through bioluminescence at night if disturbed. Appearing mostly in the southern Bay, the moon jelly's clear, disk-shaped bell is fringed with hundreds of short tentacles.
These true jellies can grow up to about 12 inches in diameter and temporarily shrink to one-tenth their size to conserve energy when no food is available. Sea nettles eat zooplankton and small fish, worms, and crustaceans. Their tentacles are covered in stinging cells called nematocysts, which stun or kill prey. The nettle uses its oral arms, which hang from the center of the bell, to move food to its mouth.
When oysters are in their floating larval stage they are prone to predation by nettles and comb jellies. Although both eat larval oysters , the sea nettle spits them out unharmed. Because the nettle has few natural predators sea turtles being one , their abundance is more affected by rain and heat. Since they like warmer saltier water, more nettles are likely during dry, hot summers.
In case you needed another reason to fight for clean water, getting our Bay back in balance with healthy fish and turtle populations may help control the nettle. In the meantime, I suggest avoiding swimming on windward shores, where jellies tend to traffic jam.
And, if stung, apply vinegar, which keeps unfired nematocysts from stinging. If the sting is still bothersome, remember the nettle was just drifting around the Bay eating oyster enemies. Forgiveness is a funny thing.
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