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Most fish swim in the typical forward-facing manner. Occasionally, they might tilt their heads downward to search for food on the ocean floor or blend into seagrass, but this is only a temporary stance. The shrimpfish (Aeoliscus punctulatus), however, is an exception, as it spends its entire life swimming vertically with its head pointed downward.
Biologists Frank Fish (an aptly named researcher) and Roi Holzman explain that the shrimpfish's unusual posture stems from its center of buoyancy being closer to its tail than its center of gravity. The duo observed the fish at an Israeli aquarium, sparking their interest in studying its stability and movement.
During a recent presentation at the Society for Integrative and Comparative Biology meeting, the researchers revealed that the shrimpfish's body is uniquely adapted to its vertical stance. Its broad, rounded back and tapered sides create a shape reminiscent of an airplane wing. Unlike most fish, which have a dorsal fin on their back, the shrimpfish's dorsal fin is located on its underside. This fin, along with its tail and anal fins, helps propel the fish forward and enables it to turn swiftly, even performing graceful pirouettes.
Despite their unusual posture, shrimpfish are not confined to it. As Richard Dawkins notes in The Ancestor's Tale, "When threatened, they can quickly switch to a horizontal position and dart away with remarkable speed."
These videos showcase fish gracefully gliding through the water, displaying both their standard swimming posture and their unique headstand maneuvers.
