Cannibalistic jellyfish have flooded the waters of a major tourist destination, multiplying rapidly and destroying fishermen’s livelihoods. The creature is the warty comb jelly, also known as the sea walnut, which has spread throughout Venice’s lagoon system after arriving from the western Atlantic, likely via ships’ ballast water. Researchers say the species’ sudden dominance reflects environmental shifts that have made once-hostile waters newly welcoming. Rising water temperatures and favorable salinity linked to “ongoing climate change” are thought to have helped the species proliferate. The animal is best known for its ability to eat its own offspring and for possessing a transient anus that appears only during defecation. Researchers from the University of Padua and the National Institute of Oceanography and Applied Geophysics say jellyfish numbers have exploded, creating acute problems for local fishermen. The jellies clog nets and devour fish eggs, larvae, and plankton—key building blocks of the lagoon’s ecosystem. Known formally as Mnemiopsis leidyi, the species is listed among the world’s 100 most harmful invasive organisms. Findings from the two-year study documenting the jelly’s spread were published in Estuarine, Coastal and Shelf Science.
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