Earth’s Greatest Scuba Divers


water scavenger beetle, Tropisternus lateralis (Hydrophilidae) with air bubble gill. Cattle tank, King Anvil Ranch, Santa Cruz Co., Arizona USA

With history dating all the way back to 500BC, human’s have seemingly always been drawn to the vast undersea, in spite of the fact that our anatomy diverged to adapt in the completely opposites direction.

By the winter of 1943, two French citizens; an engineer (Émile Gagnan) and a naval lieutenant (Jacques Cousteau), had invented the first widely available Self-Contained Underwater Breathing Apparatus, then branded as Aqua-Lung. The mysterious beauty of the marine underworld drew millions of people towards the water sport, and since then, SCUBA diving has been a safe, popular and effective way for the intrigued to explore the ocean, both recreationally and scientifically.


As big of an achievement as it is, human’s were in fact not the first animals to effectively transport a sufficient supply of oxygen with them in order to reap the advantages that lie naturally out of their reach. Some phenomenal species of aquatic insects, such as water Beetles, have been practising this skill for millions of years.

water beetle The most important properties of water for an aquatic Beetle in comparison to a human, are exceptionally different, yet crucial to both. Water Beetles can effectively manipulate water’s surface tension in order to formate a bubble of air that is trapped below the Beetle’s outer wings (elytra), or trapped against specialized hairs, in order to enable the Beetle to dive below the surface of the water. Here, the endless opportunity for periphyton and the  lack of competition illustrates why this is such an evolutionary imperative for the insect.

Acting as a “physical gill”, the air bubble, holding a mixture of gases including crucial oxygen  molecules, is hauled below the surface of the water with the Beetle. Through aerobic respiration, the air bubble’s concentration of oxygen decreases rapidly, while the concentration of carbon dioxide spikes swiftly. Resultantly, the concentration gradient between the surrounding water and the air bubble is extremely high, and this leads to a net movement of O2 molecules passively diffusing into the air bubble, with the excess CO2 passively diffusing out of the air bubble, along the concentration gradient. n air bubble with a very large surface area works the most efficiently for this process, however with time, the size of the air buble inevitably decreases as nitrogen diffuses into the air of the bubble, decreasing the rate of gas exchange. However, the bubble can easily be reformed by a swift return to the surface.



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