Jellyfish

Jellyfish

When we go swimming we try and avoid jellyfish because of their painful sting. In this page you will learn more about this creature and see how it plays it’s part in the Chesapeake Bay’s ecosystem.

One of the creatures you might see and want to avoid is the Jellyfish or Sea Nettle. They are known for the painful sting that happens when you brush against their tentacles. The portion of their tentacles that cause this sting are called Nematocysts. These are spring loaded hollow tubes filled with venom. When an object brushes up against a Nematocysts the tube pierces the skin and injects venom. This venom causes the stinging feeling when you brush against a Jellyfish. The jellyfish uses these stinging cells to disable it’s prey. After reading this you ask yourself how do you avoid being stung? Frequently we just keep an eye out for them hoping to spot them before being stung. After doing some research I have found some surprising methods to avoid stings. One is to rub petroleum jelly such as Vaseline on your exposed skin. This fools the Jellyfish into thinking you are not prey and it doesn’t sting. Another is to wear a Lycra bodysuit which allows a thin layer of protection. The third is a lotion called SafeSea that fools the jellyfish much the same way a clownfish fools an anemone.

What do you do if you have been stung by a Jellyfish? The first thing to do is remove the tentacles and get out of the water. Avoid rubbing the area as it will cause any Nematocysts to inject all their venom. There are plenty of remedies available in your local grocery store.

  • Use a credit card to scrape or tape to remove all of the Nematocysts off.
  • Meat tenderizer-These contain one of two chemicals called papain or bromelain. These chemicals break down proteins that the venom is made of.
  • Vinegar and saltwater- A 50-50 mixture helps change the ph and neutralize the venom.
  • Lime juice- A similarly diluted mixture of lime juice will have the same effect as vinegar.

Jellyfish use their stinging cells to capture their food which consist of copepods, minnows, bay anchovy eggs, worms and comb jellyfish. The jellyfish constantly feeds and each of it’s tentacles can operate independently of each other. It has an incomplete digestive system so it opens it mouth to insert food as well as expel waste. A large adult Jellyfish can produce as many as 40,000 eggs per day! These eggs attach to the bottom on things like, oyster shells and grasses. Each of these attached eggs, called a polyp, produces about 45 juvenile Jellyfish. Once they grow to the size of an inch and half they start to reproduce and lay the eggs of the next generation. This cycle continues from May until August when water temperature start to get colder. At this time the polyps attached to the bottom go dormant until temperatures rise the next summer.

Why are there more jellyfish during certain times of the year? Jellyfish require warm water temperatures, lower salinity (amount of salt in the water) and food. Areas of the bay that are shallow and close to where rivers empty into the bay, like the Potomac and Rappahannock rivers. This is because the freshwater reduces the salinity of the water and nutrients from runoff water feed the Jellyfish’s prey. Typically the Jellyfish are more common during the time from June through August.

After all of this you might wonder are Jellyfish good for anything? Surprisingly jellyfish are actually helping the declining oyster population in the bay. Comb jellies (not true Jellyfish) prey on oyster larvae (young oysters). Jellyfish eat comb jellies and also eat oyster larvae. But there is a twist, studies have shown that Jellyfish spit oyster larvae out unharmed after eating them.

More sources of information on Jellyfish on the internet…

Wikipedia-Jellyfish

Jellyfish in the Chesapeake and nearby waters

Sea Nettle forecast for the Chesapeake Bay

Coastal Watch – Sea Nettle FAQ

Maryland Marine Notes

How stuff works – Jellyfish

SafeSea Products