Israeli Team Finds Predator That Could Shift Jellyfish Blooms
Israeli researchers said Wednesday they have identified an Indian Ocean sea slug now hunting jellyfish polyps off Israel’s coast, a twist that could change the size and timing of jellyfish swarms across the Eastern Mediterranean. The University of Haifa announced that the brightly colored species, Caloria militaris, has established itself in regional waters and preys on the tiny, rock-clinging stage that later releases free-swimming jellyfish—offering a new lever on a phenomenon that clogs nets, stings swimmers, and disrupts coastal industries each summer.
The findings, published in Frontiers in Zoology, draw on lab work in which slugs collected in Israeli waters survived up to 255 days and ate as many as 192 polyps per day. Because polyps seed future blooms, steady predation could dampen swarms or shift when they peak. That prospect matters for fisheries, tourism, and even power stations that grapple with jellyfish at intake pipes.
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Scientists frame the newcomer as part of a broader reshaping of the Mediterranean. Warmer seas and the Suez Canal have opened a highway for “Lessepsian” migrants from the Red Sea and Indian Ocean, accelerating the arrival of reef fish, invertebrates, and jellyfish that compete with native species and redraw food webs. Israel has long contended with mass appearances of jellyfish such as the nomad jellyfish along its beaches; an invertebrate that targets the bloom’s source could introduce a measure of natural control—yet it is also an invasive predator with its own risks.
For now, researchers say the slug’s appetite makes it a species to watch: a small, vivid hunter that may nudge the Mediterranean’s balance forward or backward, depending on local conditions and what it eats next.
