To maintain stability underwater, divers often equip themselves with an inflatable vest or a slightly deflated suit. The water strider (Anisops deanei), which swims on its back, employs a similar system.
According to researchers Philip Matthews and Roger Seymour from the University of Adelaide (Australia) in the journal Nature, the water strider inflates a gas bladder before diving and adjusts the volume of this bladder to maintain its position underwater.
The researchers noted that other aquatic insects use gas bladders for diving. These gas bladders function like gills to retrieve dissolved oxygen from the water, which limits their diving capabilities. They often float on the surface or cling to submerged objects.
The advantage of the water strider is that it transports oxygen thanks to hemocyanin – just like divers. When placing the water strider on an extremely sensitive electronic scale, the two researchers measured changes in pressure within its gas bladder. They concluded that the water strider breathes within its gas bladder when submerged. Its hemocyanin is saturated with oxygen. Once underwater, the water strider retrieves the necessary oxygen to remain suspended and maintain its balance.
