Britannica Illustrated Science Library: Fish and Amphibians by Encyclopedia Britannica

Author:Encyclopedia Britannica [Britannica, Encyclopedia]
Language: eng
Format: epub
Published: 2011-10-29T23:50:43+00:00

58 DIVERSITY

FISH AND AMPHIBIANS 59

Out of the Water

EYES

WATER RESERVES

GILLS

Atlantic Mudskippers

Large and prominent to

Cavities for storing

Located in a type of

(Periophthalmus barbarus)

provide a panoramic

reserves of seawater.

cavity that contains

view, they are

This way the gills never

both water and air.

These are the only water-dwelling fish

protected by a delicate

dry out when the fish is

They can absorb air as

that can adapt to a completely

layer of skin. The fish

out of water..

long as they are kept

amphibious lifestyle. What's their secret?

rotates its eyes to keep

moist.

They accumulate water in their skin and in

S ome species of fish can breathe and live out of the water. They include the mudskippers in southeast Asia, which can stay on muddy flats and even climb trees. To breathe, they need only their skin to stay moist, thanks to the function of certain cells in their skin. A them moist.

several special chambers near their gills,

which enables them to use their gills outside few other species still have rudimentary lungs like those of the first aquatic animals that the water. They live on the coasts of the

colonized dry land.

Indian and Pacific oceans, in southeast Asia, and on the western coasts of Madagascar.

They usually swim in shallow waters, holding onto roots and seaweed and raising their

heads out of the water. They move about

easily on mud and dry land, and they can even Fish with Lungs

climb trees. They can breathe air or water

SOUTH AMERICAN LUNGFISH

equally well.

Lungfish have rudimentary lungs that

Lepidosiren paradoxa

originate from a connection between the

has a small gill apparatus and two

swim bladder and the esophagus. This allows

MOUTH

lungs with which it breathes during

the swim bladder to function using air when the AND THROAT

the dry season..

fish leaves the water. Depending on the species, also contain

SKIN

the fish can breathe air occasionally or even respiratory

The skin is a respiratory organ and

indefinitely. Many varieties of these fish have WEST AFRICAN LUNGFISH

organs.

needs to be kept moist. The skin

been found in fossil form all over the world,

Protopterus annectens annectens

cells are able to accumulate water.

which indicates that they were very widespread has fleshy fins that look like limbs

during the Mesozoic Era. They were probably

and three external gills. In the dry

FINS

the first vertebrates to develop lungs. However, season it secretes a substance for

Used for walking and

lungfish species are found in only three areas covering itself. It can remain in this

jumping when outside the

VENTRAL DISK

today, all in freshwater environments.

state for up to a year.

water, they even enable the

Modified fins act

fish to climb trees. In

as a lever for the

water, the fish

fish to lift itself

MUSCULATURE

crawls along the

onto roots and

is adapted to its

QUEENSLAND LUNGFISH

bottom.

tree trunks.

sculpted body to enable

9 months

Neoceratodus forsteri

it to jump in the mud.

When forced to breathe air for long

This gives the fish its

Length of time certain

periods, this fish will die. It can

common name.

lungfish can live buried in

reach up to 50 inches (1.25 m) long,

the mud

weigh 22 pounds (10 kg), and live

more than 65 years..

WATER LEVELS DROP

1

HEAD FIRST

TURNING AROUND

2

3

HIBERNATION

4

The fish looks for an area

On entering the burrow head

The lungfish curls in on itself

The fish breathes through

with soft mud under the

first, the fish secretes thick

with its head up. Before the

two or

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