EPOW - Ecology Picture of the Week

Whirligigs

Whirligig Beetles (Dinuteus sp. or Gyrinus sp.), Family Gyrinidae
Equateur, Democratic Republic of the Congo

Explanation:  What are these tiny fish, swimming in circles in this backwater pool, here in the middle of the Congo River Basin of central tropical Africa?  

Why, these are no fish, they are whirligig beetles.  

Whirligigs are common and minute inhabitants of freshwater lakes, ponds, and streams, found worldwide among a dizzying array of 15 genera and about 700 species, of the family Gyrinidae.  

They serve as scavengers of dead plants and animals on the water surface, and are distasteful (aposematic) to predators and fish and can thus thwart being preyed upon.  

Cool fact:  their eyes are in two parts so they can see above and below the water at the same time!  One study (listed below) found that the corneas of their eyes are split, with the top, above-water part covered with "maze-like nanostructures," and the bottom, below-water part smooth.  The nanostructures serve a similar purpose of anti-reflective coating on sunglasses, helping them avoid glare in the open air.  

Simply amazing for so simple a creature!  

   
Information:
     Blagodatski, A., M. Kryuchkov, A. Sergeev, A.A. Klimov, M.R. Shcherbakov, G.A. Enin, and V.L. Katanaev.  2014.  Under- and over-water halves of Gyrinidae beetle eyes harbor different corneal nanocoatings providing adaptation to the water and air environments.  Scientific Reports 4(art. no. 6004):doi:10.1038/srep06004.