Jellyfish at the Biodôme

Moon jellyfish
Jellyfish at the Biodôme

The Gulf of St. Lawrence ecosystem has been enhanced by a new habitat for moon jellyfish, invertebrates that are spectacular to watch and fascinating to discover. So that you have a better understanding of the technical knowhow needed to ensure their well-being, allow me to present their new environment.

Primitive animals

Marine invertebrates whose origins date back over 500 million years, jellyfish belong to the same taxonomic group as corals and anemones. They are made up of over 95 percent water and have the appearance of a gelatinous bell from which tentacles dangle that serve both to defend them and to gather the particles that they feed on: plankton, fish larvae, and so on. These fascinating creatures have neither a brain nor a specialized system for digestion, for regulating their mineral content, for circulation, for excretion or for breathing. Only a primitive nervous system enables them to detect certain stimuli like physical contact and light.

With the current

Their ability to get around is limited to pulsations of their umbrella, which are insufficient to fight currents. Which is why they drift with those currents, generally close to the surface. Jellyfish have few enemies apart from certain predators like some tuna, the leatherback turtle and the sunfish. And in the face of pollution or a warming of the water, their populations can explode, which has an impact on fish populations thanks to a consequent overconsumption of plankton and fish larvae. And they can create problems for humans by blocking certain infrastructures and by invading tourist beaches.

Cloning or division

There are between 1,500 and 2,000 species of jellyfish, but only 56 species colonize Canadian coastal environments, one of those being the moon jellyfish (Aurelia aurita). Jellyfish are either male or female. During breeding, eggs and sperm are released into the water, and fertilization ensues. Minuscule planktonic larvae are born, then drift for a period of time before settling on the ocean floor, where they’re transformed into a polyp resembling a tiny sea anemone. That polyp may produce other polyps through cloning (budding), or divide transversely, forming free little discs that will later transform into jellyfish.

Living in captivity

Although a good number of zoological institutions present jellyfish to their visitors, these species are fragile because of their gelatinous consistency and the way they live. Normally not set up for it, traditional aquariums require specialized equipment to keep jellyfish suspended in the water without their hurting themselves by bumping into the walls of their aquarium. A light circular and laminar current is created in cylindrical or rounded exhibition pools. It causes the jellyfish to move in a circular way, while keeping them away from the walls. In captivity, jellyfish are mostly fed on small planktonic organisms that are either raised or frozen. It’s possible to breed jellyfish by collecting eggs and sperm and placing them in contact, and by letting the little just-born larvae settle on rigid panels laid out in aquariums to perpetuate their cycle.

See also: Unsuspected wealth

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