Underwater ecosystems are a world apart. Down here the forms of locomotion, or rather, swimming are very different. We are used to seeing the flapping of fish, the rhythmic contractions of jellyfish or the scurrying of lobsters; even in rivers, we can observe insects capable of walking on water, such as shoemakers. Well, it turns out that in Australia some small beetles have developed an unusual and surprising ability: these beetles are capable of “walking” underwater, upside down, taking advantage of surface tension just like shoemakers do, but from the opposite side ( known as the water-air interface).
They are most likely beetles of the Hydrophilidae family . This finding was described by scientists John Gould and Jose. W. Valdez in Ethology magazine on June 28 of this year. The researchers define this horizontal movement of the insect as a push on the physical substrate created by the water molecules on the surface, in tension due to the cohesion forces that bind them together. In their study they allege that “our field observations revealed that the beetle could rest and move along the surface of an inverted ephemeral pool without penetrating the surface above.”
If you don’t believe it, you can see it in this video:
There are still some seemingly unanswered questions, such as:
How do these beetles keep from drowning? Scientists also have an interesting answer to this phenomenon: “The beetle had a layer of air trapped along its abdomen that allowed it to breathe and it advanced by walking, with apparent deformations of the water surface each time a leg came into contact. ”, They allege. This would be the first visual evidence of this ability of aquatic beetles.
And finally, how are they able to stay upside down? For this, the scientists have formulated a hypothesis: “we propose that the air bubbles located in the abdomen and / or the legs may be providing the upward force necessary for the beetle to be pushed against the lower part of the water surface” they say in their study.
At the moment, there are few forms of life described, capable of using this means of locomotion. If you want to observe these beetles, do not hesitate to visit them in Down Under, colloquially and ironically as the islands of Australia and New Zealand are known. Who knows how many more mysteries nature awaits us, both in and out of the water.
References:
Gould, J., & Valdez, J. W. (2021). Locomotion with a twist: Aquatic beetle walks upside down on the underside of the water’s surface. Ethology, 127(8), 669–673. https://doi.org/10.1111/eth.13203
Winter, L. (2021, July 15). Australian Beetles Walk on the Underside of Water’s Surface. The Scientist Magazine®. https://www.the-scientist.com/news-opinion/australian-beetles-walk-on-the-underside-of-water-s-surface-68981
