Today we shall take a little adventure down to the South Pacific, where you can find any number of fascinating creatures including the spotted jelly, Mastigias papua. They also go by the name, “lagoon jelly,” because you will find them in lagoons, bays, and harbors. This cute, chubby jelly has multiple mouth openings located on the oral arms which are located around the mouth. These oral arms hold the cnidocysts, stinging cells, which helps them to paralyze their prey.
Like most other jellies, the spotted jelly primarily feeds on zooplankton. It has a predator-prey relationship with its food, but it has another type of biological relationship that should be noted. Spotted jellies play host to symbiotic algae. Symbiotic or symbiosis is a word you may not have heard before, but you may have seen it in action. Symbiosis is the relationship between two different living organisms where on lives on the other and one or both depends upon the other. Who benefits determines the type of symbiosis. Perhaps you’ve heard of fleas? That is a symbiotic relationship known as parasitism, and your dog or cat is probably not very happy about it! Or maybe you’ve seen images of whales with barnacles on their chins? Those barnacles get to hitch a free ride through plankton and krill swarms as the whales feed, allowing them to eat as the whale swims. Since the whales don’t benefit or suffer either way from their little hitchhikers, this is known as commensalism!
These algae live within the tissue of the jelly, which gives the spotted jelly its brownish color. These jellies travel to the surface of the water to feed on zooplankton, simultaneously getting more sun to help with the algae growth. They then are able to harvest some of their food straight from the algae. Another way that these jellies help with the algae growth is by diving into deeper waters, which lack oxygen (anoxic), where they are able to absorb ammonium for fertilizer! Unlike parasitic symbiosis, the algae and the jelly enjoy a mutualistic symbiosis where each reaps some benefit from the presence of the other.
Challenge at home: See if you can find 3 other animal relationships and decide if it is an example of
1) parasitism, 2) commensalism, or 3) mutualism!
Tell us what type of marine life you would like to read about in future weeks!
Edited by KC O’Shea
Photography by Hayley Usedom