Aggressive jellyfish eat offspring to survive

Thousands of invasive Leidyi jellyfish in the Baltic Sea began to eat offspring at the end of the summer in order to survive the food scarcity.

According to research published May 7 in the journal Communications Biology, cannibalism is just part of the lives of jellyfish living in nutrient-poor waters outside their natural habitat, helping them have the energy to survive for a few more weeks after slaughtering local prey populations.

Two young jellyfish in the bag lead food into the mouth of an adult jellyfish. (Photo: Live Science).

"In a way, the whole jellyfish population acts as a whole, in which the juvenile group provides food for the adult jellyfish to overcome the stresses of nutrient resources," said Thomas Larsen, co-author. Research at the Max Planck Institute of Human History in Jena, Germany, said. "This allows jellyfish to survive extreme events and food shortages, adapting to a variety of climatic systems and conditions."

In the new study, the authors tracked the population of the Leidyi jellyfish (Mnemiopsis leidyi) living in the Kiel Fjord, a long bay on the Baltic Sea near northeastern Germany. The comb is native to the western Atlantic Ocean near North America and South America, but introduced into the relatively cold Baltic Sea in the 1980s. This invasive species is facing a food shortage. much longer than its Atlantic counterpart. However, they still find a way to thrive.

The success of the jellyfish in the Baltic Sea is partly due to the reproductive cycle. In the late summer, jellyfish breed quickly, each jellyfish releasing hundreds of eggs and sperm into the water at the same time, causing the number to increase thousands of times. The army of larvae is ready to eat every prey they can find, mostly small zooplankton until there is nothing left. Not long after the local prey population collapsed, jellyfish larvae also starved to death.

While taking samples of the Baltic comb jellyfish population and their prey in August and September 2008, the team discovered an adult jellyfish with two juveniles in its pouch leading the food directly into its mouth. This is evidence that helps explain that adult jellyfish continues to grow for weeks after prey and larvae die. But to confirm cannibalistic behavior, researchers need to confirm that adult jellyfish takes nutrients from young animals.

In September 2016, the team raised adult jellyfish and larvae in the laboratory. Within 36 hours, the adult jellyfish ate any juveniles in the tank. Subsequent analysis showed that the carnivorous larvae accounted for about 4% of the total carbon and 2.5% of the total nitrogen in the body of each adult jellyfish, suggesting that they have a higher nutrient density than the same jellyfish group Only eat crustaceans. "We have found the first evidence that adult M. leidyi jellyfish eat their own larvae. Because the larvae cannot survive the winter in northern habitats, we speculate the main purpose. M. leidyi larvae store energy and nutrients for adults , " the researchers said.

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