Jellyfish: All Stings Considered

Written By Chase Mullins

Yesterday, I visited Point Lookout State Park in southern Maryland. This is considered the point where the Potomac river converges with the Chesapeake Bay. However, the park is also known for its historical significance during the Civil War. Over 52,000 Confederate soldiers were imprisoned here and faced many challenges, such as starvation, smallpox, and direct exposure to adverse weather.

The fishing pier at Point Lookout State Park, which overlooks the Chesapeake Bay.

The fishing pier at Point Lookout State Park, which overlooks the Chesapeake Bay.

My boyfriend and I were walking along the shore of the Potomac River and dipping our toes in the water occasionally to cool ourselves. Suddenly, my boyfriend jumped backward, which startled me. He said he saw a jellyfish. I concentrated for a few minutes on the shallow water until the translucent figure was visible. Then of course, I pulled out my phone and snapped a few pictures. See if you can spot the jellyfish in the photograph below (I’ll post the answer at the bottom of the post).

There is a jellyfish above. Yes, I promise. Once you see it, you can’t un-see it.

There is a jellyfish above. Yes, I promise. Once you see it, you can’t un-see it.

I never knew there were jellyfish in the Bay or the Potomac. From my childhood, I remember seeing dead jellyfish washed ashore in the morning along the beaches of North Carolina. Besides the aquarium, I had never seen a live jellyfish in my life. So then the questions started pouring in, what do jellyfish eat? How do they eat? Why and how do they sting? Thankfully, jellyfish are well-studied creatures. Here’s what I learned:

Three species of jellyfish can be found in the Chesapeake Bay; sea nettles, moon jellyfish, and lion’s mane jellyfish. The biggest jellyfish in the Chesapeake Bay is the moon jellyfish which can grow up to 10-12 inches in diameter! Sea nettles and lion’s mane jellyfish primarily prey upon fish, shrimp, comb jellies, and other small creatures. While moon jellyfish eat plankton, mollusks, crustaceans, and copepods. The signature translucent, gelatinous, bell-shaped body is called a medusa. Attached to the medusa are stinging tentacles, which paralyzes the prey. Once the prey is paralyzed, they move the food to their mouths, located under the center of the medusa (1).

The beaches along the Chesapeake Bay. Visible in the background is the fishing pier in the photograph above.

The beaches along the Chesapeake Bay. Visible in the background is the fishing pier in the photograph above.

The jellyfish sting is a self-defense mechanism designed to immobilize prey, caused by specialized cells called cnidocytes which contain structures called nematocysts. When the tentacles brush against a potential predator it triggers a coiled up barb to shoot into the victim (2). If you’d like a helpful visual, I’d suggest heading to this website: https://www.science.org.au/curious/people-medicine/all-about-jellyfish-stings.

The barbs contain venom which enters the victim upon puncture. The venom contains porins, neurotoxic peptides, bioactive lipids, and other small molecules. Porins, which are a type of protein, “punch a hole” in the membrane of many types of cells, such as blood, skin, and nerve cells, leading to a disruption of normal function. When porins form a pore in the membrane of a red blood cell, it initially leads to the release of potassium and then minutes later leads to complete hemolysis, which can lead to cardiac arrest. The types of porins vary between species, thus resulting in differing intensities of stings among species (3).

Angel A. Yanagihara and Ralph V. Shohet study the physiology of a jellyfish sting at the University of Hawaii. They have found that porin assembly can be inhibited by zinc. In their 2012 study, they injected mice with venom from the Australian box jellyfish and found that zinc gluconate inhibited the efflux of potassium from the mice red blood cells, which prolonged their survival time. The authors of this study have suggested that the administration of zinc in a timely manner could be critical in saving human sting victims (4).

This is the same photograph as above, except the jellyfish is circled. Did you find it?

This is the same photograph as above, except the jellyfish is circled. Did you find it?

Jellyfish have a network of nerves called a “nerve net” that allows them to sense their environment. This delicate network allows them to sense changes in water chemistry or if a potential predator is around. Jellyfish can tell what direction they are facing by specialized structures called statocysts and they can detect the absence or presence of light through their light-sensing organs. Jellyfish have some incredible defense adaptations, such as bioluminescence and the ability to camouflage themselves. Their colorless bodies are difficult for predators to detect, as I’m sure you realized while trying to find it in the picture (5).

After researching jellyfish for this blog post, I’ve become fascinated with their invertebrate way of life. With no “brain”, bones, heart, or “eyes”, it’s intriguing to learn how their physiology has evolved to allow them to thrive. While I admire their unique way of life, I wouldn’t want to be anywhere near a jellyfish without protection or some zinc in hand, just in case.

References:

(1) https://www.chesapeakebay.net/discover/field-guide/entry/jellyfish

(2) https://www.science.org.au/curious/people-medicine/all-about-jellyfish-stings

(3) https://www.smithsonianmag.com/science-nature/whats-behind-that-jellyfish-sting-2844876/

(4) Yanagihara AA, Shohet RV (2012) Cubozoan Venom-Induced Cardiovascular Collapse Is Caused by Hyperkalemia and Prevented by Zinc Gluconate in Mice. PLOS ONE 7(12): e51368. https://doi.org/10.1371/journal.pone.0051368

(5) https://ocean.si.edu/ocean-life/invertebrates/jellyfish-and-comb-jellies

Chase Mullins