How Mangrove Fish and Mudskippers Live on Land

Amphibious Fish Breathe Air and Walk Around

Aug 4, 2009 Megan Jungwi

Some fish are able to leave the water and breathe air on land. This requires special adaptations to their gills.

The defining feature of a fish is its aquatic nature – fish live in water and are not supposed to leave it. Yet many fish defy convention and hop onto land including the killifish and mudskippers of the world’s mangrove forests. These fish do not have lungs and must adapt their gills for terrestrial living. Here’s how these amphibious fish do it.

Why Gills Normally Don’t Work on Land

Fish obtain their oxygen from the water they live in. However, water has less oxygen per part than air, so fish need an efficient system to gain all the oxygen they need. Professor Carl Hopkins of the Cornell Center for Materials Research explains how gills work and why they don’t work on land in “Gills key to how fish breathe”. Gills are made up of highly branched capillaries with thin walls. This provides a large surface area for gases such as oxygen to diffuse into the fish’s system; gills also bring red blood cells closer to the surrounding water making diffusion easier. The network of capillaries is fragile however and when a fish is brought onto land the capillaries collapse under their own weight. In water, the fish’s gills are buoyant and thus don’t collapse. Some fish though have evolved a way to use their gills on land.

The Killifish Lives in Trees

The mangrove killifish (Kryptolebias marmoratus), also sometimes called the mangrove rivulus is a Western Atlantic fish that can live on land for up to 66 days. Aalok Mehta describes this unique fish in the November 6 2007 National Geographic article “Fish Lives in Logs, Breathing Air, for Months at a Time”. This hermaphroditic fish has adapted to the fluctuating water levels of mangrove swamps by “logpacking”. These two-inch fish will pack themselves into hollowed out logs and wait for the return of water.

How the Killifish Breathes

As Mehta describes, the killifish is able to live on land by filling its gills with a mass of cells that provide support to the capillaries. The fish thus alters its biology to live on land. Further it seems that this fish is able to excrete waste products, such as nitrogen, through its thin skin. K.J. Ong et al. describe an experiment proving the growth of an interlamellar cell mass (ILCM) in the killifish’s gills in their 2007 Journal of Experimental Biology article “Gill morphology of the mangrove killifish (Kryptolebias marmoratus) is plastic and changes in response to terrestrial air exposure”.

The Mudskipper Lives on Land

The mudskipper is a mangrove fish of the Gobiidae family that spends much of its time out of water. As the National University of Singapore describes on its webpage “Guide to the Mangroves of Singapore>Mudskippers” this fish has leg-like pectoral fins that enable it to crawl onto land and climb trees. It can also breathe through its skin as long as it stays damp. K.J. Ong et al. describe various ways mudskippers are able to breath on land. The gills of mudskippers are structurally different from water-bound fish. Some mudskippers have gill lamellae spaced wider apart, or the lamellae are thicker and longer, to prevent collapse. Other species of mudskippers have fusions between the capillaries to keep them from collapsing.

So Many Amphibious Fish

There are many more amphibious fish that are able to breathe air. Jeffrey B. Graham describes a variety of fishes in the book Air Breathing Fishes including blennies in Panama, walking catfish, and the lungfish which does have lungs. However, many of the fish listed in the book are freshwater, not marine, animals.

The copyright of the article How Mangrove Fish and Mudskippers Live on Land in Marine Biology & Oceanography is owned by Megan Jungwi. Permission to republish How Mangrove Fish and Mudskippers Live on Land in print or online must be granted by the author in writing.