The cytoplasmic lifeform vessel was a type of ship used by cytoplasmic lifeforms native to an area of the Delta Quadrant. It was equipped with a weapon capable of draining an enemy ship's energy reserves.
In 2375, one such vessel attacked the USS Voyager on the mistaken belief that the crew had kidnapped one of their kind. In actual fact, it had attached itself to Lieutenant B'Elanna Torres and only after intense surgery did the ship's EMH managed to remove the creature and have it transported back to its ship. As a result, the ship withdrew. (VOY: "Nothing Human")