sea walnut

sea walnut (plural sea walnuts)

1. A comb jelly in the genus Mnemiopsis, native to the western Atlantic Ocean but invasive around the world.
   • 2012, Caspar Henderson, The Book of Barely Imagined Beings, page 318:

     In the early 1980s the Warty comb jelly or Sea walnut was introduced (probably from the ballast water of ships from North America) to the Black Sea, a habitat in which it had no natural predators. By the summer of 1989 it was proliferating in such numbers and consuming so much plankton in the Black Sea that the fisheries dependent on the plankton crashed.