Jellyfish, anemones and corals, Oh my! While the National Museum of Natural History (NMNH), is perhaps better known for exhibits, specimen collections, and research, the museum recently came alive as guests got to watch the feeding of live critters of the “stinging-celled” group Cnidaria. This outreach event in the Q?rius Education Center proved wildly popular, with nearly 600 visitors during a two-hour period!
This spectacle piqued a lot of curiosity, leading to a lot of interesting questions. Thankfully many of us -- including experts on jellyfish and their relatives, Allen Collins, Bastian Bentlage and Cheryl Lewis Ames along with volunteers/interns Matt Snyder, Mehr Kumar, Tara Lynn and myself -- were on hand to answer as many questions as possible. Here are some things that curious visitors asked us about these weird and wonderful invertebrates and their stinging weapons.
Q: Do all Jellyfish sting?
All jellyfish do have stinging cells. In fact, the possession of stinging cells, or cnidocytes, is the defining characteristic of Cnidaria, the phylum to which jellyfish, as well as anemones, corals, hydroids, siphonophores, etc. belong. However that does not mean that all cnidarian stings would bother YOU. While the sting of a jelly is usually fatal to their prey, most do not have stinging structures large enough to pierce the thick skin of human beings. Mostly when we enter their environment (anywhere in the ocean), we do not notice their stings, or they only result in mild irritations. However some types of jellyfish, such as the box jellyfish, can be extremely dangerous and even fatal to humans.
Q: What should I do if I get stung? Should I really pee on it?
Thankfully most jellyfish stings are mild, and require little or no treatment. If a sting is severe, contact emergency medical services right away. The recommended first aid for a jelly fish stings begins with flooding the area with household vinegar to remove any visible tentacles. Emersion in hot water, especially with Epsom salts is also helpful in providing pain relief and breaking down the venom. Hot water is recommended as part of first aid for many types of marine stings, for instance urchins and sting rays. While there is no evidence to show that urine would make a jellyfish sting worse, there is also no evidence that it helps either, and certainly damage to your dignity is a possibility. Personally I would stick with vinegar.
Q: How do the stinging cells work? Is it an allergic reaction like a bee sting? Is there an electrical shock, like an electric eel?
A jellyfish sting is not an electric shock like one might receive from an electric eel, nor is it an allergic reaction or like a bee sting. Rather, it is your body’s complex response to a complex biological structure known as the nematocyst. This structure consists of a fluid filled capsule, under very high pressure, containing a long inverted tube, which often has spines and sometimes a piercing barb. When stimulated by mechanical or chemical cues, this tube will evert explosively. So, when a person is stung by a jellyfish, the body has to deal with hundreds or thousands of stinging cells' thread-like barbs being embedded in the skin. In addition, and often more seriously, a sting victim's body has to deal with the jellyfish’s venom, which is a cocktail of different substances. Because of the complexity of cnidarian stings and their health impacts, this remains an active area of scientific research. As an example, one recent paper identified the most damaging venom component in a box jellyfish as a pore-forming protein, or porin. This porins cause holes in cells. When holes are formed in red blood cells, potassium is released. While a daily banana is a good thing, too much potassium causes hyperkalemia, which impacts cardiovascular function and can ultimately stop one's heart.
Visitors who wanted to know more had the opportunity to go speak with Dr. Angel Yanagihara, who was "The Scientist Is In", in the Sant Ocean Hall. A Biochemist and expert on box jellies and their venom, Angel started studying jellies after own nasty encounter with the sting of a box jellyfish. Here she is giving a TEDxHonolulu talk on her research.
Q: What do you feed the jellyfish and how do they eat it?
All the cnidarians in our lab are fed brine shrimp. When the shrimp come into contact with the tentacles of the jelly, anemone or coral, they are stung and stick to the tentacle. The prey are then transferred to the animal’s mouth and consumed.
Q. Do they ever get bored of eating brine shrimp?
In the wild jellyfish and other cnidarians have a diversity of prey items. However, the animals in our lab seem to be perfectly happy to eat brine shrimp all of the time! Interestingly, predation is not the only way in which cnidarians get nutrients. Many cnidarians, including several in our lab, harbor symbiotic algae (zooxanthellae) that photosynthesize and provide nutrients to their cnidarian hosts.
Q. How many species of jellyfish are there, and where do they live?
Cnidaria is a hugely diverse group of animals with approximately 12,000 known species. And there are certainly many more to be discovered. There are three main groups within Cnidaria: 1) Anthozoa, which includes stony corals, octocorals, and anemones (approximately 6,000 species); 2) Medusozoa, with roughly 4,000 species including the so-called true jellyfish, the box jellyfish, the stalked jellyfish, and hydrozoans (hydroids, siphonophores, fire corals and hydromedusae); and 3) Myxozoa, which is a group of approximately 2,000 species of parasites. Cnidarians can be found in ocean all over the world. There are even some freshwater species, including the freshwater jellyfish Craspedacusta that we keep in our lab.
Q. Do jellyfish have brains?
Jellyfish do not have a brain in the way that we think of them. There is no centralized nerve center. However, jellyfish and other cnidarians do have nervous systems that allow them to perceive and react to the environment, activate muscles in coordinated fashions, and sometimes exhibit complex behaviors. For instance, recently it was shown that some jellyfish can sense ocean currents and swim against them. Also, we cannot neglect to mention the amazing, intimate courtship of one box jellyfish, Copula sivickisi.
Q. Can jellyfish see?
Many jellyfish do indeed have primitive light sensing structures called ocelli, which can sense different light levels, but do not form an image. Some jellyfish have taken it above and beyond. Box jellyfish not only have simple eyes but also have true image-forming eyes complete with retinas and lenses!
Q. Do jellyfish have ears?
While jellyfish certainly do not have ears like we do, one wonders if they can hear. They do possess structures, called statocysts, that allow them to sense orientation in the water column, similar to the inner ear in a human. Could they possibly "hear" vibrations in the water around them? It might sound a bit like a crazy question, but it turns out that scientists have asked the same question about octopus statocysts and whether those allow octopods to hear. Which one of our visitors is going to be the first to act on his or her curiosity and test whether jellyfish are sensitive to vibrations? After all, curiosity acted upon is science!
What would you like to know about jellyfish and their relatives? Let us know!