Some comb jellies cannibalize their young when food is scarce
Some jellies go ballistic when their prey disappears — cannibalistic that is. Warty comb jellies, native to the western Atlantic Ocean, invaded Eurasian waters in the 1980s. The jellies have since flourished, cycling through population booms during summer when prey is abundant and busts in fall and winter when it’s not. Now a study finds that to persist when food is scarce, adult jellies eat their young. Understanding how a “brainless, fragile animal” conquers new environments could reveal new ways to control the invasive species, says Jamileh Javidpour, a marine ecologist at the University of Southern Denmark in Odense. Javidpour and her colleagues collected adult and larval comb jellies (Mnemiopsis leidyi) from Kiel Fjord — an inlet of the Baltic Sea east of Germany — in August and September of 2008, before and after the jelly population collapsed. As the adults’ preferred food source, small crustaceans called copepods, plummeted at the end of August, young comb jellies also began to disappear. By the end...