Some small fish uses jellyfish as a shelter to hide from predators

In the West-Indian Ocean, there is a species of jellyfish called Versuriga anadyomene (no common English name for this one, sorry!). This jellyfish does not have any tentacles, so it is not difficult to get close to, and the stingers are not really harmful to humans. However, the sting can be painful and even harmful for certain fish, so most fish tend to stay away from this jellyfish.

What is really cool is that there have been observations where small fish have been seen to use the V. anadyomene as a floating shelter from the predatory cornetfish (Fistularia spp.). The do this by hiding inside the helmet, and a single jellyfish can shelter many fish at the same time.

An image of a somewhat related jellyfish, because it was impossible to find a picture of the V. anadyomene that I could use with permission. This jellyfish is morphologically much like it, so you get an idea of what it looks like. The fish will live under the helmet. Image by Shinji, posted with the Creative Commons Attribution 2.0 Generic license.

The V. anadyomene is a plankton-eater, so it will continuously filter water in its mouth to get nutrients, and the small fish feed on the leftovers to survive inside the jellyfish. At a certain size, they decide that it is time to leave the jellyfish permanently, and will then take their leave. It is currently not known if the jellyfish get any benefit or even loss from this relationship, so we don’t know if this is a mutualistic, parasitic or commensalistic symbiosis.

The stingers on the jellyfish is dangerous to both the fish hiding in the jellyfish and the cornetfish. However, the small fish are able to avoid it because of their small body size, but the poison is deterring the cornetfish from getting too close. It might make a few attempts at snatching the small fish, but is usually not successful. The result is that it is a pretty good shelter for small fish, which increases their survival chances compared to living alone in open water. Of course, there is a chance that they might be stung by accident, but this risk is lower than taking their chances in open water.

This is far from the only jellyfish to provide shelter

There are many jellyfish where other species have been observed in their helmet, using it as a shelter. Some scientists even speculate that some species might use this as a permanent shelter, but due to the fact that jellyfish is a somewhat unstudied type of animal, we don’t really know for sure yet. However, what is sure is that both crabs, fish, sea spiders, mollusks, brittle stars and turtles have been observed under the helm of a jellyfish.

A video of the phenomenon

This YouTube video shows the jellyfish and the cornetfish in action, so you can take a look at what I am talking about. In my opinion it looks really cool, so let me know in the comment field if you agree.

Thanks for reading this short post. If you want to learn more, check out this article by EarthTouch News where I first read about it.

About the author

Hi, I’m @valth! I live in Norway with my girlfriend, our newborn son, and our two dogs, one of which is seen wearing a bow tie in the profile picture!

I am very passionate about nature and biology, and have been studying ecology for a few years now. My passions are mostly within conservation biology, mycology (the studies of mushrooms), animal behavior and general microbiology. I really enjoy both the theoretical aspect, as well as the more practical aspect of biology, and I spend about as much time in front of biology textbooks as I do spend on finding and identifying plant, mushroom and animal species in the forests.

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