When we say that someone is a “fish out of water,” we sometimes mean to suggest that they are uncomfortable or out of their element. Yet in nature, there are fish supremely adapted to life outside of water. These are amphibious fish-species that have evolved strategies to survive in both aquatic environments and on land. Of these, the mudskipper is arguably the most competent land-dweller, often fuzzing the line between fish and terrestrial animal.Mudskippers not only survive on land but also feed, socialise, defend territory, and even reproduce on land. Their study provides a rare window for scientists into one of the major evolutionary milestones: how aquatic life first moved onto land.
Mudskippers and their unique adaptation to life on land
Mudskippers aren’t the only fish capable of moving outside their natural environment. Lungfish, as their name implies, have lungs as well as the capability to suffocate if underwater too long. Another type of fish, the eel catfish, can slither across the land to catch insects in the mud, while the famous sand-crawling behavior of grunion fish is used to lay their eggs in the sand on the beaches of California.What is amazing about mudskippers, though, is that they have become completely acclimated to life on the land. Unlike most other amphibious fish species, mudskippers are mostly found on land. These species are found in Africa, South Asia, Southeast Asia, and South America. There are about 25 species of mudskippers. These species can be found on muddy coasts, mangrove swamps, estuaries, and swampland. These are areas where the land and the sea meet, and where things are always changing.This is because they inhabit this “in-between world,” which makes them so important as a subject in the field of evolutionary biology. According to reports, the mudskipper fish can shed some light on the possible evolution of life from water to land thousands of years ago.
How mudskippers breathe on land
Since fish are known to breathe through gills, what mechanism does the mudskipper have for respiration in air?Mudskipper has developed two ingenious approaches. First, they use skin respiration, which means they are able to take in oxygen from the surroundings simply by using their skin, as well as the inside of the mouth and throat, where oxygen is stored in the capillaries.In order for all this to work, these fish need to have moist skin. This is why mudskippers are often seen rolling around in mud and splashing in shallow puddles.Their second method is their gills. Mudskippers trap or store water in their chambers, then move around while holding the trapped air. Some of their species can often be observed to be picking water from their environment, then expanding their gill covers before moving back to their activities on the land.
How a fish learns to walk
Mudskippers walk on land using their pectoral fins in a way analogous to limbs. These fins have flexible joints, somewhat like shoulders and elbows, which allow the fish to push themselves forward, prop their bodies up, and even do push–up–like movements.This style of motility likely evolved in aquatic environments. Many fish species, especially gobies (which are near relatives of mudskippers), utilize their fins to brace against surfaces in flowing water. The mudskipper merely adapted this ability onto land.Besides “walking,” mudskippers can hop. Flipping their tails into a C-shape-a reflex called a C-start-they thrust themselves into the air. This behaviour originally evolved as a predator-escape mechanism in water, then proved useful on land.
Mudskipper burrows and territorial behaviour on land
When tides alter or when it’s hot outside, mudskippers seek protection in their extensive underground burrowing systems. The burrowing systems of mudskippers are also surprisingly intricate and serve several purposes in mudskipper life cycles. They can offer protection against predators or serve as breathing sites.As a way of digging, mudskippers will gather large amounts of mud in their mouths, which they will then carry outside, gradually hollowing out long burrows. Other mudskipper species will occasionally trap air bubbles in these burrows while swimming, effectively creating a private oxygen supply! Mudskipper burrows have been observed with elevated doorway entrances which serve as observation points as well. From these mud-stands, mudskipper observation occurs, studying anything from food sources, competitors, threats, to prospective mates! Finally, mudskipper males are anything but passive, as they fiercely defend their territory, often in ‘dramatic’ showdowns as a way of protecting it from rivals, with ‘wide open mouths, raised dorsal fins, shoving matches, etc.’These visual displays also play a role in establishing dominance and reduce the need to engage in perpetual physical combat—a case for land-based behaviors adapting in a fish.
Mudskippers surprising trait
One of the mudskipper’s most surprising traits is its ability to blink something typically associated with land animals.Their eyes sit high on their heads like periscopes, giving them a wide field of view above water. Blinking helps keep their eyes moist, cleans away debris, and protects them from sudden threats.Rather than developing new muscles, mudskippers repurposed existing eye muscles to retract their eyeballs into fluid-filled cavities inside the skull. This efficient evolutionary shortcut shows how complex behaviors can arise without drastic anatomical changes.
What mudskippers teach us about evolution
Mudskippers represent a living example of evolution in action. By studying how they breathe, move, see, and behave on land, scientists gain clues about how early vertebrates may have made the leap from water to land; a transition that eventually led to amphibians, reptiles, mammals, and humans.Some researchers even speculate that if climate change drastically alters Earth’s ecosystems in the distant future, amphibious fish could once again exploit newly available land environments.For now, mudskippers remain a fascinating reminder that evolution doesn’t always follow clean boundaries and that sometimes, a fish really can walk on land.