In a small pond, a walking catfish finds itself in a predicament. The pond, once a haven, has become overcrowded, and food is scarce. Fortunately, this fish has a unique ability that many others lack: it can leave the water and embark on a terrestrial journey in search of better opportunities. However, this journey is fraught with challenges, including the risk of suffocation, dehydration, physical harm from rough terrain, and predation by land animals.
While we typically think of fish as strictly aquatic creatures, the walking catfish is just one of hundreds of fish species that are actually amphibious. These fish possess adaptations that allow them to survive on land. Amphibiousness in fish exists on a spectrum. At one end are species like the mosquitofish, which only venture onto land when absolutely necessary. At the other end are species like mudskippers, which comfortably hop around mudflats for extended periods.
The reasons for fish leaving water vary. For some, like the mangrove rivulus, high temperatures in their shallow tropical pools prompt them to seek cooler, shaded areas on land. During dry periods, they can survive for up to two months out of water by staying in moist environments. The eel catfish, on the other hand, ventures onto land to satisfy its appetite for beetles. For others, such as the California grunion, the move is part of a reproductive ritual, with masses of fish flopping onto beaches to lay eggs before returning to the ocean.
Underwater, fish breathe using gills, which absorb dissolved oxygen from water. However, in open air, gills collapse and become ineffective. Amphibious fish have developed alternative breathing methods. The armored catfish, for instance, uses its blood vessel-rich stomach to breathe air. Lungfish, related to the ancestors of all tetrapods, possess true lungs and can drown if submerged for too long.
Fish have thin, permeable skin that facilitates the exchange of essential compounds while underwater. On land, this trait leads to moisture loss. To combat dehydration, mudskippers roll in mud, while lungfish create a mucus cocoon to survive dry seasons, waiting for rain to revive them.
Amphibious fish use powerful fins and innovative strategies to navigate land. The Nopoli rock-climbing goby, for example, scales Hawaiian waterfalls using suction cups on its mouth and pelvic fins. The mummichog searches for reflective surfaces to find water, while mosquitofish use their inner ear to orient themselves on slopes, moving downhill to locate water. The walking catfish relies on taste buds concentrated in its whiskers to detect nearby water and prey, avoiding foul waters with hydrogen sulfide.
Despite the challenges of terrestrial life, amphibious fish have evolved remarkable adaptations to overcome them. They are resilient in the face of droughts and floods, gain access to new prey, and have an escape plan if their aquatic environment becomes competitive, polluted, or unhealthy. For these species, being a “fish out of water” provides a significant advantage.
Using clay or other craft materials, create a model of an amphibious fish, such as a walking catfish or mudskipper. Pay attention to the unique adaptations that allow it to survive on land, such as specialized fins or gills. Present your model to the class and explain how these adaptations help the fish in its terrestrial journey.
Imagine you are an amphibious fish like the eel catfish or the California grunion. Create a survival guide that includes tips on how to avoid predators, find food, and stay hydrated while on land. Use illustrations and diagrams to make your guide engaging and informative.
In groups, create a role-playing game where each student takes on the role of a different amphibious fish species. Develop scenarios where you must navigate various challenges, such as finding water, avoiding predators, and dealing with environmental changes. Use dice or cards to introduce elements of chance and strategy.
Research different amphibious fish species from various parts of the world. Create a presentation that includes information about their habitats, behaviors, and adaptations. Share your findings with the class, highlighting the diversity and ingenuity of these remarkable creatures.
Conduct a science experiment to simulate the challenges amphibious fish face on land. For example, you could test how different surfaces affect the movement of a model fish or explore how moisture levels impact the survival of a simulated fish skin. Record your observations and discuss how these experiments relate to the real-life adaptations of amphibious fish.
Amphibious – Referring to animals that can live both on land and in water. – Frogs are amphibious creatures because they can breathe air on land and swim in water.
Fish – A cold-blooded animal that lives in water, has gills for breathing, and usually has fins. – The goldfish is a popular pet that lives in water and has bright orange scales.
Land – The solid part of the Earth’s surface that is not covered by water. – Many animals, like deer and rabbits, make their homes on land where they can find food and shelter.
Water – A clear, colorless liquid that is essential for all living things and covers about 71% of the Earth’s surface. – Plants need water to grow and stay healthy, which is why we must water them regularly.
Adaptations – Changes in an organism that help it survive in its environment. – The thick fur of polar bears is an adaptation that keeps them warm in icy habitats.
Breathing – The process of taking in oxygen and releasing carbon dioxide. – Humans and animals rely on breathing to get the oxygen they need to live.
Survival – The ability to continue living or existing, especially in difficult conditions. – Many species have unique survival strategies to find food and avoid predators.
Dehydration – A condition that occurs when the body loses more water than it takes in. – Animals in the desert must find water regularly to avoid dehydration and stay healthy.
Navigation – The process of determining one’s position and planning a route to a destination. – Birds use the sun and stars for navigation during their long migrations.
Environment – The surroundings or conditions in which a person, animal, or plant lives. – Protecting the environment is important for keeping our planet healthy for future generations.
