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Newts and European Salamanders: Salamandridae - Behavior And Reproduction

eggs sperm species water

Most newts and European salamanders live on land as adults but move to water to breed. Some of these animals stay in the water for several months around breeding time, but the amount of time spent in the water varies greatly among species and even sometimes within one population of the same species. Newts that lay eggs one at a time have longer breeding seasons and, thus, spend more time in the water, because it takes many weeks for a female to lay all her eggs. Species that lay their eggs in clusters spend little time in the water.

Scientists know little about the behavior of newts and European salamanders during the land-dwelling, because these animals are rarely seen. At least some species, especially eastern newts, have highly developed sensing powers that help them to return to the same breeding ponds each spring. These newts can detect at least one thing in the environment that gives them directional information, such as a smell, the position of the Sun, the pattern of light in the sky, or the direction of the magnetic field of the Earth.

When bothered by predators, some newts raise their heads, chests, and tails to show the bright colors on their bellies. These newts often rock back and forth and release a strong-smelling poison through their skin. The poison of some newts is one of the most powerful natural toxins.

During mating, a male places a sperm bag close to a female and then pushes her over it or uses displays to lure her over it, so that she takes the sperm up into her cloaca, and it is united with eggs inside her body. The cloaca (kloh-AY-kuh) is the chamber in some animals that holds waste from the kidneys and intestines, holds eggs and sperm that are about to be released to the outside, holds sperm entering a female's body, and is the passage through which young are born. The female stores the sperm in special organs in her body until she is ready to lay her eggs. Some females lay single eggs on the leaves of water plants and then wrap the eggs in leaves to hide them from predators such as fish.

WHAT'S THE DIFFERENCE?

There is no simple way to tell newts and salamanders apart. Species that spend a long period each year living in water and becoming temporarily adapted to life in water are called newts.

Transfer of sperm in a sperm bag has two interesting consequences. First, it is unreliable: In some species, many sperm bags are missed by females. Second, rival males can interfere. For example, in several species rival males mimic female behavior, causing the original males to release sperm bags that are not picked up by females. To make sure this does not happen and to make sure their sperm gets into a female, some males defend females by picking them up and carrying them away if a rival male approaches.

Chemical communication is important in the mating of newts and European salamanders. Males have glands that release scented chemicals that make females receptive to them.

In most species of newts and European salamanders the females lay their fertilized (FUR-teh-lyzed) eggs. The eggs hatch into larvae that live in the water for a while and then go through metamorphosis to become adults. In four species of European salamanders, however, the females keep the fertilized eggs inside their bodies and give birth to large larvae or, in some instances, young salamanders that look like adults but are not ready to reproduce. In these four species only a small number of eggs complete development. In Caucasian salamanders only two fully developed young are born after three or four years inside the female. Fire salamanders, alpine salamanders, and Lanza's alpine salamanders also reproduce this way.


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