Fact vs. fiction: 3 things you thought you knew about jellyfish

Jellyfish. Jellies. Sea nettles. Whatever you call them, the likelihood of running into these stinging tentacled creatures generally increases in the summer.

This medusa belongs to the genus Cyanea, a jellyfish well-known to bloom and occur in large numbers in surface waters.

This medusa belongs to the genus Cyanea, a jellyfish well-known to bloom and occur in large numbers in surface waters. (Image credit: NOAA)

Jellyfish have a complicated relationship with humans: They are often feared by beachgoers because of their sting. They can get unintentionally caught up in commercial fishing nets. Some jellies can even clog intake pipes of coastal power and desalination plants, and in high concentrations, can force closures of popular beaches.

For scientists, however, jellyfish are fascinating research subjects – they play important roles in the marine ecosystem and are a key source of food for some fish and sea turtles. Some even protect commercially valuable species, such as oysters, from predators.

Whatever your view may be, many misconceptions exist about jellyfish. Let’s bust the Top 3 myths:

MYTH #1: Jellyfish are all the same species
On the contrary, there are more than 200 documented species of true jellyfish (and many more of their stinging relatives) across the globe. The environmental conditions required for each species to thrive can differ. In fact, NOAA and Smithsonian Institution scientists recently found that sea nettles in the Chesapeake Bay are considerably different than those in the open ocean and recognized it as a new species.

The jelly (hydromedusa) is in a family of hydromedusae called Rhopalonematidae, which is known for the canals running vertically on the inside of the bell, gonads attached to these canals, and sometimes having two sets of tentacles. In this video, you can see the perfectly relaxed arrangement of the two sets of tentacles; scientists think this is a position that allows for optimum feeding in the midwater environment at 3,000 meters. (NOAA Office of Ocean Exploration and Research, 2017 American Samoa expedition)

MYTH #2: Jellyfish "go after" people
Not true. Any contact with jellyfish is incidental. Humans are not on their menu, but when we are in their environment we can get in the way of their tentacles. While jellyfish don't have a brain, they can sense light and have coordinated swimming behaviors, which help keep them in good places to hunt for microscopic plants and fish eggs/larvae, or other prey like fish, worms, and crustaceans.

This stunningly beautiful jellyfish was seen during Dive 4 of NOAA's 2016 Deepwater Exploration of the Marianas expedition on April 24, 2016, while exploring the informally named "Enigma Seamount" at a depth of 3,700 meters. Scientists identified this hydromedusa as belonging to the genus Crossota. Note the two sets of tentacles — short and long. At the beginning of the video, you'll see that the long tentacles are even and extended outward, and the bell is motionless. This suggests an "ambush predation" mode. (NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas.)

MYTH #3: Applying urine to a jellyfish sting can reduce the pain
Perhaps the most interesting of myths, the use of urine to treat stings has been tested and proven unhelpful. A better idea? Try an acidic liquid like vinegar. There are also several commercially available products marketed for stings.

What to do if you get stung: First, look for any tentacle adhering to skin, and flush the area well with cold ocean water. Do not rub the sting area because you could inadvertently distribute the venom further into the body. Then vinegar or evidence-based commercial product should be applied if there is continuing pain.

A new tool undergoing testing
NOAA scientists are working on a way to forecast jellyfish, using the Chesapeake Bay as a testing ground, so residents and business owners can understand the probabilities of encountering jellies based on changing environmental conditions – such as salt concentration and temperature of bay water.

More > Get your fill of facts about jellyfish biology and their life history offsite link – including some more stunning close-up photos.