How lizard tail-shedding?

University of Michigan ecologists and colleagues have found the answer to a question that has existed for more than a century: What is the main factor determining lizards' ability to shed tail?

The answer is just one word: Venom

Self-tails are a common way to defend predators in lizards. When attacked, most lizards throw away their 'hungry' and flee. Predators often eat the tail while the lizard is lucky to escape. After that, the lizard's tail will regrow itself.

The lizard's ability to shed its tail from one species to another, and from one location to another, has many variations. For more than a century, biologists suspect this transformation is controlled by pressure from predators: As the number of 'lizard-eating' animals increases, the need for defense mechanisms This effective defense also increased.

When lizards live near animals that want to hunt them, they tend to develop the ability to shed their tails easily, because this feature allows them to survive longer to reproduce and transfer genes to the next generation. according to the.

However, loss of tail also has long-term consequences, including reduced flexibility, lower social status and slower growth. So from an evolutionary perspective, therefore, maintaining the ability to tail-shed itself is only appropriate when there are many predators around.

The team decided to test the idea of ​​predatory pressure by using a combination of laboratory experiments and field measurements carried out in Greece and the Aegean Islands, where there are very many predators live. Their conclusion? The hypothesis of pressure from predators is generally correct, but there is an unexpected point: Not all predatory species play the same role.

Johannes Foufopulos ecologist, co-author of the study published in Evolution magazine, said: 'In fact, the only really important predator is solid'.

'On the Aegean Islands, snakes are lizard hunters,' Foufopoulos, a professor at the School of Environment and Natural Resources and further explained by the Department of Ecology and Evolutionary Biology. 'So it is reasonable to assume that the lizard's defense system is aimed at their main enemy, the snake. But no one has ever discovered this connection, so far. '

A separate attack of snakes is probably the best explanation for this conclusion. When predators do not have venom attack, tail-drop tactics are only really effective in some cases quite effective, when the attack animal grabs the tail.

But when a snake spreads its fangs to attack, just touching the lizard's tail can infect deadly venom. In that case, the ability to shed tail itself within seconds - before the venom spreads to the lizard's vital organs - becomes a matter of life and death.

UM Jonhannes Foufopoulos ecologist with an Aegean lizard, one of 15 lizard species used in his study of lizards in Greece and the Aegean Islands. (Photo: Lin Jones)

Foufopoulos said: 'The lizard lost its tail, but it is still alive. And it can regrow another tail '.

Although research conducted in the Mediterranean region, Foufopoulos believes that this result can be applied in other parts of the world - such as the Southwestern Americas or Australia - where lizards coexist with snakes toxic.

Greece and the thousands of islands in the Aegean region are ideal for studying the evolution of animals, and each animal group adapts to the individual conditions of each island. This situation is similar to Darwin's study of the sparrow's differences in the Galapagos Islands.

Millions of years ago, when the sea level was lower than today, the Aegean Islands were part of the mainland, and the whole area shared a set of predators. Today, predators include mammals such as foxes and jackals, as well as snakes and birds for example hawks, falcons, cypress, and crows.

Over the millennia, rising sea levels and thousands of Aegean islands have been formed. Gradually, the diversification of predatory species on these islands decreases. Today, some Aegean islands have no snakes.

The research team searched for a correlation between the automatic rate and the presence or absence of some predatory species in the 10 collecting areas of the study. Automatic rate is a measure of how easy the lizard can shed its tail. The higher the ratio, the easier it is to lose the tail.

The most obvious signal in the research process is the relationship with snakes.

The team found that lizards on uninhabited islands often lose the ability to shed their tails themselves. In contrast, in all places where snakes live, lizards have a high auto-rate.

The study included more than 200 insect-eating lizards of 15 species, ranging in size from 5 to 8 inches, from the nose to the caudal tip.

To determine the automatic rate, researchers combined field observations and laboratory measurements. In the field, lizards that have shed their tails and new tails can be distinguished from lizards that still have their original tails.

In the laboratory, the researchers used a light poke on the lizard's tail with a determined force for 15 seconds. The rate of laboratory automation for each species is expressed by the time that the lizard shed its tail.

Understand the distribution of tail-docking ability in different lizards with important applications for conservation biologists. Because of the importance of tail-shedding ability, as a predator defense system, demonstrating this ability can help predict which lizards are most at risk.

As the extinction in other Mediterranean islands shows, lizards have lost the ability to shed their tails themselves, unwilling to protect themselves from snakes. The main author of the article is Panagiotis Pafilis of SNRE. Co-authors include Foufopoulos, Nikolaos Poulakakis of Yale University, Petros Lymberakis of Crete Natural History Museum and Efstratios Valakos of Athens University.

The study was funded by the School of Natural Resources and Environment under UM and the modern Greek Program of UM.

Refer:
1. Panayiotis Pafilis, Johannes Foufopoulos, Nikos Poulakakis, Petros Lymberakis, Efstratios D. Valakos.Tail Shedding In Island Lizards [Lacertidae, Reptilia]: Decline Of Antipredator Defenses In Relaxed Predation Environments.Evolution, 2009;DOI: 10.1111 / j.1558-5646.2009.00635.x