The ocean is home to marine creatures that move through water in a way that truly resembles flight, often called “flying snails.” These organisms navigate their watery world with a unique propulsion method, allowing them to soar through currents. This remarkable adaptation showcases their unique place in the vast marine environment.
Unveiling the “Flying Snail”
The creatures known as “flying snails” are pteropods, also called sea butterflies. These marine snails are gastropod mollusks that live a pelagic lifestyle, inhabiting the open ocean rather than the seafloor. Many pteropod species have delicate, transparent calcium carbonate shells. However, some species, like sea angels (Gymnosomata), lack shells entirely. Their “flight” is a specialized form of swimming, allowing them to drift and propel themselves through the water column.
The Mechanics of Their Movement
Pteropods achieve their distinctive “flying” motion using specialized anatomical features called parapodia. These are wing-like extensions of their foot, a structure typically used for crawling in other snails. Pteropods rhythmically beat or flap these parapodia, generating lift and propulsion to move through the water. Their fluid movement has been compared to the figure-eight wing pattern of flying insects like fruit flies, and they even use a “clap-and-fling” motion to enhance lift. While their movement appears like flight, it is a highly adapted form of swimming in a dense aquatic environment.
Life in the Open Ocean
Pteropods are globally distributed across all major oceans and latitudes. They typically inhabit the upper layers of the open ocean, usually within 0 to 200 meters of the surface, though some species can be found in deeper zones, even down to 4,000 meters. As zooplankton, they play a significant role in marine food webs. They primarily feed on phytoplankton, microscopic plant-like organisms, and small zooplankton by trapping them in a sticky mucous net. Pteropods serve as a food source for a variety of larger marine animals, including commercially important fish like salmon, herring, and mackerel, as well as squids, large shrimp, and whales.
Facing Environmental Challenges
Pteropods face threats from ocean acidification, a direct consequence of increased atmospheric carbon dioxide. As the ocean absorbs more carbon dioxide, its pH levels decrease, making the water more acidic. This acidity impacts shelled pteropods by reducing the availability of carbonate ions, the building blocks for their calcium carbonate shells. Acidic conditions can make it difficult for pteropods to build and maintain their shells, potentially causing existing shells to dissolve. This vulnerability has broader implications for the marine food web, as their decline could disrupt the food supply for many species that rely on them.