Comb jellies use cannibalism to survive long winters

A new study has revealed that the prolific comb jelly, an invasive marine species from North America, uses cannibalism to survive long winters. The jellies feed on blooms of their own offspring to persist in the nutrient-deprived waters. 

As non-native species are increasingly disrupting ecosystems in a changing climate, it is important to understand the strategies and traits that allow them to survive. 

Comb jellies have been very successful in expanding their ranges from the east coast of North and South America to the coast of Eurasia. 

It has been challenging for scientists to understand how the invasive jellies manage to colonize local habitats, where they cause a lot of economic and environmental damage.  

Instead of storing resources for the winter, the jellies invest seemingly unnecessary energy in massive “blooms” of offspring that do not survive long winters in nutrient-deprived waters.

Scientists assumed that comb jellies were able to persist thanks to a lack of predators, but the new study links their success to cannibalism.

The research was focused on comb jellies at their northernmost range in the Baltic Sea off of northern Germany.

“We combined a study of the population dynamics of this species with experimental feeding and geochemical tracers to show, for the first time, that adult jellies were actually consuming the blooms of their own offspring,” explained study lead author Professor Jamileh Javidpour.

The discovery sheds new light on why the jellies invest so much energy in the blooms of offspring before wintering. The blooms serve as floating nutrient reservoirs that persist beyond the collapse of normal prey populations. 

The consumption of offspring was found to provide adults with an additional two to three weeks of growth, which is essentially the difference between life and death. 

“In some ways, the whole jelly population is acting as a single organism, with the younger groups supporting the adults through times of nutrient stress,” said study co-author Thomas Larsen.

“Overall, it enables jellies to persist through extreme events and low food periods, colonizing further than climate systems and other conditions would usually allow.”

The findings may ultimately help to combat the spread of comb jellies,  which can negatively impact native species as well as local fisheries. In their non-native ranges, the comb jellies have been particularly successful in places with rapidly warming seawater, overfishing, and excessive nutrient loads.

The study also indicates that cannibalism may be much more widespread in the animal kingdom than what was previously realized. 

While cannibalism is known to occur in times of extreme shortage or disaster across many species, the new research shows that it can occur under regular conditions.

“Because comb jellies trace their ancestry back to the beginning of most animal life as we know it during the Cambrian Period, 525 Million Years Ago, it remains possible that it is a basic, unifying feature across the animal kingdom,” said Professor Javidpour.

The study is published in the journal Communications Biology.

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By Chrissy Sexton, Earth.com Staff Writer