Osmosis as nature's method for establishing optical alignment.

For eyes to maintain optimal focus, precise coordination is required between lens optics and retina position, a mechanism that in vertebrates is governed by genetics, visual feedback, and possibly intraocular pressure (IOP). While the underlying processes have been intensely studied in vertebrates, they remain elusive in arthropods, though visual feedback may be unimportant. How do arthropod eyes remain functional while undergoing substantial growth? Here, we test whether a common physiological process, osmoregulation, could regulate growth in the sophisticated camera-type eyes of the predatory larvae of Thermonectus marmoratus diving beetles.