On the way back from Newfoundland I didn’t expect to see any exciting wildlife. Of course, I kept my eyes peeled for moose, but once again saw none. But I wasn’t too bummed about it – after all I’d decided the last post about Newfoundland was going to be the minke whale, so I sat quietly and enjoyed the car ride. When we got to Quebec City, however, we took a wrong turn and ended up at the aquarium. It seemed like fate, and since we had a lot of time to kill we bought some passes and went to explore.
The aquarium had a pretty awesome jellyfish wing. There were tons of different tanks all lit up in the dark so the jellies danced and spun majestically in a plethora of changing colours. One tank, however, was just lit like a regular aquarium tank, and contained some of the coolest jellyfish I’d ever seen. They were all attached to the bottom of the tank, with the dome part facing the ground and the tentacles pointing up. They were so funny looking I just had to blog about them, so today’s post is about these little cuties, the up-side down jellyfish.
Up-side down jellies live in shallow tropical waters, where they can get a large amount of sunshine. This is very important for the up-side down jellyfish, because it has a friendly relationship with an algae, Symbiodinium microadriaticum. The algae lives right underneath the jellyfish’s bell, and so the jelly must flip over to give the algae sunlight. This allows the algae to perform photosynthesis, creating organic nutrients which the jellyfish can then absorb.
This method of obtaining nutrients works quite well for the jellyfish; even though it has to spend most of its time up-side down, it gets a free meal out of it. Unfortunately this isn’t enough to completely satisfy the jellyfish, so it gets further nutrients either by filter feeding or capturing prey with its tentacles. The barbed tentacles of the up-side down jellyfish are triggered only when two stimuli are detected. One responds to mechanical stimuli, and the other only to chemical stimuli, specifically amino acids. Once the barb has fired, the cell dies, so the set of conditions that cause a barb to fire are very prey specific. After all, waste not want not.
Up-side down jellyfish do not begin their lives attached to the sea floor. After hatching from eggs attached to their mother’s body, tiny little pre-jellyfish swim around until they find a a suitable place to attach themselves, and then they start their epic transformation into adult jellyfish. After enough algae has settled on the now sedentary youth, it goes through a series of budding and regrowing that result in the formation of a fully adult jellyfish.
Up-side down jellyfish can reproduce sexually or asexually; the sessile polyp (before it has settled and attached itself to the floor) can bud when resources are abundant. Adult jellyfish, however, can only reproduce sexually. Males release sperm into the water which fertilizes the eggs of a nearby female, which are then incubated and eventually hatch.
The special relationship that up-side down jellyfish have with algae isn’t the only interaction with other species the jellyfish has. Certain sea turtles feed on them, and some very intelligent crabs pick them up and place the jellies on their backs. This gives the crabs extra protection from predators, though what the jellyfish think about this no one knows.
I was really excited to see these jellyfish at the aquarium, and learning about them has been awesome. They also look extremely funny in the water, because they still beat their tentacles like normal jellyfish, but they are facing into the ground. So it looks like the jellyfish are very confused, or drunk or something. I want a tank of them now.
Cover image By WereSpielChequers – Own work, CC BY-SA 3.0