As It Happens

Invasive comb jellies cannibalize their own young, study finds

A species of jelly is resorting to cannibalising its own babies in order to thrive in new habitats and survive periods of low food, new research has found. 

'We had [seen] cannibalism in animals like fish and squids, but not in a jelly,' Jamileh Javidpour says

A comb jelly floats with two baby jellies trapped in it body (marked with red arrows). (Jamileh Javidpour/University of Southern Denmark)


A species of jelly is resorting to cannibalizing its own babies in order to thrive in new habitats and survive periods of low food, new research has found. 

Jamileh Javidpour, the study's lead author, says this is the first time invasive comb jelly — a close relative to jellyfish — have been observed feeding on their own larvae.

"We had [seen] cannibalism in the higher animals like fish and squids, but not in jellies," she told As It Happens host Carol Off.

"They are very, very simple. We call them brainless. Comb jellies don't have the complexity of higher animals and that makes them all very interesting to study. Jellyfish feed on other jellyfish species — but not on their own larvae." 

The animal doesn't have a reservoir to store energy so it will "feed voraciously" on plankton and other small marine organisms during good food seasons, she said.

Much of that energy is then dedicated to producing huge numbers of offspring. 

However, when that food runs out, rather than wasting the energy already spent on producing the offspring, the adults will switch to cannibalism in order to recuperate their losses, she said. 

The study, which was published in the journal of Communications Biology, describes this as a "bloom-and-bust" reproductive cycle.  

"It shows how resilient they are," Javidpour said. "That makes sense with them being invasive. It shows that they can switch to a behaviour that doesn't make sense in an ecological context we use for other animals."

Mnemiopsis leidyi, the warty comb jelly or sea walnut, is a species of tentaculate ctenophore, originally native to the western Atlantic coastal waters, but invasive in European and western Asian regions. (IrinaK/Shutterstock)

Around the Black Sea and Caspian Seas, the comb jelly has been blamed for contributing to the collapse of fisheries in the areas.

But cannibalism may be beneficial to delicate ecosystems as it can help to reduce the jellies' population, Javidpour said. 

One possible reason the behaviour had not been discovered until recently could be that the larvae's "fragile body" meant it would disappear extremely fast inside the adult jelly's stomach.  

She said the discovery may also help shed light on the "evolutionary path that this animal has taken in the last million years of surviving in different periods of the Earth."

"We have just opened a new door to many other questions that need to be answered," she said.

Written by Adam Jacobson. Interview produced by Tayo Bero.

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