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The Brilliant and Brainless Jellyfish

Residents and visitors alike know that the summer season brings a whole range of fascinating animals to our Coastal Bays watershed. As the temperature of the bays warm, we begin to see a rise in the diversity and abundance of fish, crustaceans, and other bay-dwellers. There are schools of silversides swimming through the canals, shrimp and snails clinging to our docks, and mole, hermit, and ghost crabs running around on the shore.  And if you have been around Ocean City long enough, you know July marks the unofficial return of the jellyfish.

Atlantic Sea Nettle by Wally Gobetz
Atlantic Sea Nettle by Wally Gobetz

Between their slimy, gelatinous bodies and ominous, stinging tentacles, these spineless creatures do not typically join dolphins, osprey, and the Assateague ponies on people’s “must-see” animal list for summer. But once you dive into the wonderous world of jellyfish (and jellies!), you will discover there is much more to them than you may think.


Jellyfish are, in fact, not fish at all, and they tend to be more rubbery than “jelly” like. And what the lay person calls a jellyfish, may actually end of being either a “true jelly”, or a “comb jelly”; two relatively unrelated groups of animals.  The “true jellies” belong to the phylum Cnidaria, which contain bell-shaped (adult form) jellies that pulse through the water trailing their stinging tentacles.  The “comb jellies” are part of the phylum Ctenophora. These jellies lack stinging cells and have eight rows of cilia (or combs) that run down their bodies propelling them through the water. One characteristic that these two have in common is that they lack a brain! They do have a nerve net that can sense touch and respond to changes in their environment.

Local Species

Moon Jellyfish by Zac Garmoe, DE Center for Inland Bays
Moon Jellyfish by Zac Garmoe, DE Center for Inland Bays

In Maryland’s Coastal Bays, there are a few jellyfish species that you are bound to run into on your aquatic adventures. Frequently seen down canals on the surface of the water, the moon jelly has short hair-like tentacles and is easy recognizable by their four circular gonads on the top of their bell. When a moon jelly brushes up against you in the water, the cnidocytes, or stinging cells, along their tentacles will release a stinger called a nematocyst. These are the source of the pain you feel when you come in contact with any jellyfish!

Another frequently seen jellyfish species is the Atlantic sea nettle. These menacing looking creatures have a smaller bell than the moon jelly and much longer tentacles. They are the ones we all really want to avoid as they have quite a significant sting! The sea nettle is also not a very strong swimmer. Despite being able to contract their bell, their movement is mainly controlled by winds and currents.

Pink Comb Jelly on beach by Liz Wist, MCBP
Pink Comb Jelly on beach by Liz Wist, MCBP

One of the most common seen “jellies” in the bays is the pink comb jelly. These egg-shaped jellies are present year-round, and are distinguishable with their bright, iridescent pink combs. Sea walnuts, another local species of comb jelly, closely resemble pink comb jellies, but have two longer gelatinous lobes that give them their “walnut” name. Their eight combs look colorless during the day, but when spotted at night, look greenish-yellow in color.


Ecological Importance

All jellyfish play a key role in our local ecosystem food web. They feed on zooplankton, worms, small fish, and even other jellies, keeping their populations in check. They are also a primary food source for ocean sunfish and leatherback sea turtles. Something that is very beneficial to this area, is that the sea nettle eats comb jellies, who enjoy feasting on oyster larvae. So next time you see a jellyfish in the water, give it some space, and send a little thank you their way!

Author Background

Liz Wist is the Education Coordinator at the Maryland Coastal Bays Program.  Liz is responsible for the development, creation, and evaluation of environmental education programs. Within these programs, she designs curriculum, leads interpretive programs and summer camps, mentors seasonal staff, and provides professional development for educators. Liz is also responsible for organizing and facilitating MCBP community engagement opportunities such as Discover Your Watershed, Bay Day, and Living Local. For more information on education programs, please email lwist@mdcoastalbays.org.

Maryland Coastal Bays Program
Maryland Coastal Bays Programhttp://mdcoastalbays.org
All Creature Features are written by a Maryland Coastal Bays Program (MCBP) staff member.  MCBP is a non-profit and National Estuary Program that exists to protect and conserve the waters and surrounding watershed of Maryland’s coastal bays to enhance their ecological values and sustainable use for both present and future generations. MCBP works with stakeholders on the local, state, and federal level to protect the five main bays within the watershed; Assawoman, Isle of Wight, Sinepuxent, Newport, and Chincoteague, through restoration, environmental education, scientific monitoring, and targeted community outreach.

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