Sea cucumbers breathe through their anus, pumping water in and out of internal 'respiratory trees'. Slender pearlfish take advantage of this, sliding inside, usually tail first, to hide. Some species simply use the cucumber as a shelter, while others nibble on their host's internal organs. The sea cucumber, for its part, gets no say in the matter.
In 2022, a young tagged bar-tailed godwit flew from Alaska to Tasmania in about 11 days of nonstop flight, covering 13,560 km without eating, drinking or landing. Before departure, these birds pile on huge fat reserves and shrink their digestive organs, which are useless during the journey.
To escape rivals, a dung beetle rolls its ball of dung in a straight line. At night, it holds its course using the glowing band of the Milky Way. In a planetarium, researchers showed that beetles rolled straight under a starry sky but wandered aimlessly when the galaxy was switched off. It was the first animal known to navigate this way.