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anubi writes:

Just how tiny can something be made...and still have it work?

https://www.earth.com/news/unexpected-find-inside-the-eye-of-a-tiny-wasp-megaphragma-viggianii/

Megaphragma wasps do more than just outsmart thrips. They also show how far miniaturization can go before basic features stop working.

Most insects rely on their eyes for movement and exploration. Ommatidia form the building blocks of these compound eyes and act like small detectors for incoming light.

In Megaphragma viggianii, researchers have counted a total of 29 ommatidia, which is extremely low compared to the number in the eyes of bigger insects.

Each tiny ommatidium uses a lens that measures around 8 micrometers, but that's still enough to focus light onto specialized structures below.

The rhabdom within each ommatidium (the optical units that make up the insect's compound eye) has stayed thick enough – about 2 micrometers – to catch adequate light and send signals to the brain.

This balance between lens size and rhabdom thickness seems to preserve clear vision during daylight hours.

Packed pigment granules line the sides of each ommatidium. They block stray light that might otherwise blur the wasp's vision.

Maintaining sight at such a small scale may demand a lot of energy. Some data hint at heavy loads of mitochondria in these photoreceptor cells, suggesting that vision comes with a metabolic price.

Roughly a third of the ommatidia cluster near the dorsal region of the eye. These specialized structures appear to detect polarized light, a feature known to help insects orientate under open skies.

In many insects, the dorsal rim area is essential for successful navigation and migration. It provides steady guidance, even when visual landmarks are absent.

In addition, a few unique photoreceptor cells hide behind the first row of ommatidia. They are positioned to receive light indirectly.

Original Submission