Reptiles

Turtles (Testudines)

Turtles are of the oldest animals on the planet, existing since the age of the dinosaurs (200 million years ago). They are reptiles of Testudines (Turtles) order, also called Chelonia, and have a typical cover (shell).

They are the most primitive among all extant reptiles, standing close to the common ancestor. They are spread everywhere except Antarctica. There are completely terrestrial species (land turtles) inhabiting even desert areas, as well as aquatic representatives found in salt (sea turtles) or fresh water (freshwater turtles). Their sizes vary from 11.5 cm to 180 cm, respectively with weight of several tens of grams to 590 kg.

Their typical feature is the presence of a shell (carapace), consisting of two parts - upper (carapace) and lower (breast-plate), joined laterally by a bridge.

The typical carapace consists of about 50 bones and is covered with approximately the same number of corneal spike. The breast-plate is quite monolithic, with fewer bones and corneal spike.

Turtles are poikilothermic animals, i.e. they have a variable body temperature dependent on the environment. Only one species - the leatherback turtle (Dermochelys coriacea) is able to maintain a higher body temperature than that of the surrounding habitat, through an unknown mechanism. In order to obtain the necessary heat for the activating their metabolic processes, all other species of turtles must receive additional energy from the outside - for example, from the sun rays or from warm water currents. That is why the turtles are not found in extremely cold climates. Under cooling conditions, they go into hibernation - i.e. minimization of all life processes, in which they do not take food and limit their movement. At the next warming, they resume their activity again.

All representatives breathe through quite well-developed lungs. The presence of a shell makes the act of inhalation difficult and prevents the chest from expanding. For this reason, turtles have special muscles that actively pump air into their lungs. Although sea and freshwater turtles live in water and are able to hold air for long periods of time, they must come to the surface, in order to take breath.

They reproduce through eggs, which the female lays in a pre-dug hole on land. The egg itself, as in all reptiles, is of the amniotic type. The name is due to the presence of the amnion - an internal membrane that surrounds the developing embryo and forms a space filled with liquid (amniotic fluid). This is an evolutionary advance over amphibian eggs. The amnion protects the embryo from the surrounding dryness by providing it with a watery environment. The embryo itself is nourished by the reserve nutrients in the egg - from the yolk sac.

The egg development lasts 45-90 days. When the young turtles are already fully formed, they pierce the shell with the germ tooth (caruncula), located in front of the upper jaw. They leave the nest in the sand and start living on their own. The sex of turtles depends to a large extent on the environmental factors – most notably on the ambient temperature during incubation.

The nutritional habits are different for individual representatives, as there are completely herbivores, carnivores and omnivores.

The spiny-tailed (Testudo hermanni) and spiny-thighed (Testudo graeca) land turtles are the two most common species on the territory of our country.

These two famous turtle species differ in several external markings. The spiny-tailed turtle has a tail, as the species name suggests, ending in a corneal spike.

The spiny turtle, apart from being slightly smaller in size, does not have a spine, but it has two corneal spikes on its legs. They are medium in size, about 35-39 centimeters, and the largest representatives of these terrestrial plant-eating turtles are found in our country. The spiny-thighed turtle prefers grassy terrains, unlike the spiny-tailed turtle, and is typical for sparse forests.