They can breathe in the air. They can breathe in the water. They can even breathe air when they are under the water. Apple snails (Ampullariidae) are a family of freshwater snails that are specially adapted to be amphibious, although they are classified as invertebrates.
On the right side of their bodies, these snails have gills like a fish so they can extract oxygen from the water. Opening on the left side, they have a lung to breathe when they are out of the water. Many of them also have a snorkel tube which goes to the lung, allowing them to breathe air while submerged to avoid bird predators.
Why do apple snails need to breathe both in and out of the water? These snails are native to tropical areas where there are extreme wet and dry seasons. During the rainy season, they live in the water. To find food, they spend most of their time submerged. In the dry season there might not be any water available, so lungs become necessary for survival. If the area becomes severely dry, they have a lid called an operculum which they can close to seal themselves inside their shell to prevent dehydration. Because of their ability to travel on land, they lay their eggs in clusters above the water-line on plants or trees where fish can’t eat them.
In many ways, these snails are well-designed to adapt to extreme fluctuations in moisture and avoid predation. Unfortunately, humans have transported them to non-native areas with bad results. Apple snails are popular in aquariums, and some have been released into nature when they grew too large. At other times, well-meaning people have brought apple snails into new areas to provide food. Their ability to adapt has created problems as they have become pests destroying rice and other crops. God has created a well-balanced system of living things with the ability to adapt. Many times humans have failed to respect that system resulting in undesirable consequences.
© Roland Earnst