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September is an amazing month for boating on the Chesapeake Bay and our favorite middle rivers – the Severn, Magothy and Patapsco. While the recent mornings have been cool, temps are supposed to be back in the 90’s next week so a jump off the boat may be warranted to cool off. But those darn jellyfish are still lurking around… or are they called nettles? And where do they come from anyways? Before jumping in and willingly risking a “sting”, you may find your brain overloaded with questions. So, the team at Atlantic Marinas got together with our dear friend Google to answer those questions.


Most Bay region residents use the terms “jellyfish,” and “sea nettles” interchangeably. The term you use is likely based on where you grew up. But technically, the bay nettle is a category of jellyfish (and is different from the sea nettle). Here is more detail on the species of jellyfish that can be found specifically in the Chesapeake Bay:

  • Jellyfish (the general term) have a transparent, gelatinous body and an umbrella-shaped bell called a medusa. Tentacles with stinging cells hang from the bell. The stinging cells are called nematocysts.
  • Sea nettles have a smooth, milky white bell that grows to about 4 inches in diameter. Up to 24 tentacles hang from under the bell.
  • The moon jellyfish is the Bay’s largest jellyfish. It can grow 10 to 12 inches in diameter. Hundreds of short tentacles hang like fringe from the bell’s edge.
  • The lion’s mane jellyfish has a broad, flattened bell and eight clusters of short tentacles. The noticeable difference is that the bell is usually orange-brown.
  • There’s also a Bay Nettleunique to the Chesapeake Bay and a larger ocean-going Sea Nettle. The Bay Nettle is smaller with longer tentacles than the Sea Nettle. The Bay Nettle helps oysters by eating certain predators. The sting is “moderately painful, but not dangerous unless there is an allergic reaction,” according to the Virginia Institute of Marine Science.

Jellyfish are made up of 95 percent water, so you’d think there isn’t much to them. But if you’ve ever been “stung” by one, then you know you are wrong.

How are jellyfish formed?

One day they are none and it seems like the next day there are hundreds. But where did they come from? If a sting doesn’t make you angry enough, how about their life cycle: jellyfish take on two different body forms: medusa and polyps. Polyps can reproduce asexually by budding, while medusae spawn eggs and sperm to reproduce sexually. Polyps can live and reproduce asexually for several years, or even decades. Additionally, as seawater temperature rises, predators of jellies are removed by fishing, more structures are built in seawater, and more nutrients flow into the ocean, some types of jellyfish and comb jellies may be finding it easier to grow and survive.

Why is it called a STING?

Tentacles of jellyfish have thousands of microscopic, barbed stingers. Each stinger has a tiny bulb that holds venom and a coiled, sharp-tipped tube. When you brush against a tentacle, tiny triggers on its surface release the stingers. The tube pierces the skin and releases venom.

To scientists, one of the most fascinating parts of a jellyfish is their stinging cells. Located on their tentacles, jellyfish’s stinging cells are called cnidocytes. They are small compartments that house a mini needle-like stinger. When you brush against a tentacle, tiny triggers on the tentacles surface release the tiny stingers called nematocysts in the skin. When it pierces the skin, the venom is released into the skin. All of this happens within a millionth of a second.

Treating a jellyfish sting

Combining baking soda or vinegar with seawater is recommended for washing away the micro-sized tentacles that cause the “sting” feeling. Do not rinse with fresh water (like tap or bottled water) because that can make more stingers fire. Rinsing a sting with seawater may prevent stingers from releasing more venom. Lastly, don’t rub the area, which can make it worse.

Other solutions are notated and seem to contradict each other – one says cover the area with a cold compress while another says, “take a hot shower”. If you have success with either of these, please share with us in comments.

We hope this article helps increase your knowledge of our pesky friend, the jellyfish. If anything, let’s just celebrate the saying “the more you know”.

Authors note:
In writing this article, our research utilized many different articles and websites in the Chesapeake Bay region, notated below. Information regarding jellyfish and nettles varied slightly, therefore we ask readers of this article to allow some room for variation.


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