Question

Mudskippers are tropical fish that spend much of their time on land, but have gills rather than lungs or other air-breathing adaptations. Diving beetles spend a substantial amount of time underwater, yet lack gills or other adaptations to breathe underwater. Explain how both are able to live in and out of water.

Answer 1

Mudskippers are fish and so they have gills. Once out of the water, their gills begin to dry out and stick together, so mudskippers have a special cavity behind their ears where sea water is stored. As they rotate their eyes, pressure is applied to that cavity and this reoxygenates the stored water, lubricates the gill flaps and restores the gills to their normal function.

In diving bettles, the spiracles (openings through which the beetle breathes) are on the abdomen just under the tips of the wing covers (elytra). When in a resting position, below the water surface on an incline with the head down, the beetle raises the tips of the elytra and breathes through the spiracles. When ready to dive, it stores a supply of air under its wings for breathing while under water.