The longest animal known to date is not the giraffe (the world's largest land animal, over 5 meters long) or the blue whale (up to 30 meters long), but... the worm. More precisely, the laceworm (Lineus longissimus). It measures just 10 to 15 cm in diameter, but can exceed 50 meters in length! This marine vertebrate lives in the cold waters off the coasts of Britain, Norway and Sweden. In addition to its size, its skin is covered with a deadly toxin, which serves not only as protection against predators but also as a chemical weapon.