Mudskipper

Peculiar fish that lives on land

A peculiar fish lives on tropical tidal beaches and in muddy mangrove swamps. It is called a mudskipper, and may resemble some kind of mix between a fish and a tadpole. The mudskipper is a fish that can live both in the water and on land! There are about 25 different species of mudskippers, with some species only a few centimetres long, and others as large as 30 cm. Some species of mudskippers live almost their entire lives on land. 

The fish uses its pectoral fins to drag itself or “jump” through the mud on land. This is reflected in the fish’s English name “mudskipper”. When the mudskipper is on land, it carries water in some kinds of gill chambers, much like the air tanks that divers carry with them to be able to breathe underwater. But the mudskipper also has adaptations that allow it to breathe air through the skin when it is moist. It is therefore important that the mudskipper stays moist at all times – even when it is on land. 

Better vision on land

In the mangrove swamps where many mudskippers live, the environment is highly affected by the tide. The tides depend on the gravitational pull of the moon and sun, causing the water level to rise and fall in the area. When the water level is low, the mudflats are exposed, and the mudskipper uses its water chambers for breathing on land, while defending its territory and hunting for food to eat in the mud. The mudskipper does in fact have better vision on land than in the water – and under each eye there is a small pocket of water, which the mudskipper can pull its eyes into to moisten them and not dry them out. When the water level is high, the mudskipper retreat to burrows they have dug on the bottom. The water in the burrows can become very oxygen-poor, but some species of mudskippers swallow air that they release down in the burrow, to create an oxygen-rich air pocket.

Fierce battle for the females

Mating time is important for the mudskipper. The males go to great lengths to attract the females to their underwater burrow. On land, the males perform a kind of mating dance, where they puff up their cheeks and flick their tails in order to jump. They unfold their stately dorsal fins, and develop bright colours to look extra good for the females. When a male convinces a female to mate, she follows him down into the burrow he has dug in the mud, where she then lays her eggs. The eggs are carefully guarded until they hatch after about a week – then the fry drift out to sea where they develop as plankton in the water, before swimming back into the mangrove swamp to live the rest of their lives partly on land.