Currently, the lineage from which reptiles evolved is made up of a group of animals known as amniotes, which developed a fundamental aspect to be able to completely differentiate themselves from those species that totally depended on water to survive. Its reproduction.
On our site we would like this time to present you with an article on the reproduction of reptiles, so that you can learn about this process biology in these vertebrates. Dare to continue reading to learn more about the evolutionary aspects and some peculiarities of the reproduction of reptiles.
Classification of reptiles
Reptiles are a group for which it is common to find two forms of classification:
- Linnean: in the Linnean, which is the traditional classification, these animals are considered within the subphylum of the vertebrates and the class Reptilia.
- Cladistics: in the cladistic classification, which is more current, the term "reptile" is not used, but in a general way states that the living animals in this group are Lepidosaurs, Testudines, and Archosaurs. The former would be made up of lizards and snakes, among others; the seconds, by the turtles; and the third, by crocodiles and birds.
Although the term "reptile" is still commonly used, mainly for its practicality, it is important to note that its use has been redefined, among other reasons, because it would include birds.
The reproductive evolution of reptiles
Amphibians were the first vertebrates to conquer a semi-terrestrial life thanks to the evolutionary development of certain characteristics, such as:
- Legs well developed.
- Transformation of both the sensory and respiratory systems.
- Adaptations of the skeletal system, being able to be in terrestrial areas without needing water to breathe or feed.
However, there is one aspect for which amphibians are still totally dependent on water: their eggs, and later the larvae, require a watery medium for their development.
But the lineage that includes reptiles developed a particular reproductive strategy: the development of an egg with a shell, which allowed the first reptiles became totally independent of the water to carry out their reproductive process. However, some authors believe that the reptiles did not eliminate their relationship with a humid environment for the development of the egg, but that these phases now take place within a series of membranes that cover the embryo and that, in addition to the necessary nutrients, also offer moisture and protection.
Characteristics of the Reptile Egg
In this sense, the reptile egg is characterized by having these parts:
- Amnion: they have a membrane called amnion, which covers a cavity that is filled with liquid, where the embryo floats.
- Allantois: Next is the allantois, a membranous sac that has respiratory and waste storage functions.
- Corion: then there is a third membrane called chorion, through which oxygen and carbon dioxide circulate.
- Shell: and finally, the outermost structure, which is the shell, which is porous and has a protective function.
For more information, we encourage you to read this other article on the Characteristics of reptiles.
Are reptiles oviparous or viviparous?
The animal world, in addition to being fascinating, is characterized by diversity, which is not only appreciated in the existence of so many species, but, on the other hand, each group has different characteristics and strategies that guarantee their biological success. In this sense, the reproductive aspect of reptiles becomes quite varied, so there are no established absolutisms in this process.
Reptiles show a greater diversity of strategies than other vertebrates, linked to their reproduction, such as:
- Forms of embryonic development.
- Set hold.
- Parthenogenesis.
- Sex determination, which may be linked to genetic or environmental aspects in some cases.
In general, reptiles have two reproductive modalities, so that a large number of reptile species are oviparous, that is, they females lay eggs, so the embryo will develop outside the mother's body; while another smaller group, are viviparous, so the females will give birth to already developed offspring.
But there have also been identified cases of reptiles that some scientists call ovoviviparous, although it is also considered by others as a type of viviparism, which consists in that the development of the embryo occurs inside the mother, but it does not depend on her for its food, which is known as lecithotrophic nutrition.
Types of reptile reproduction
The types of animal reproduction can be considered from various points of view. in this sense, now let's know how reptiles reproduce.
Reptiles have a sexual type reproduction, so the male of the species fertilizes the female, so that later occurs embryonic development. However, there are cases in which females do not need to be fertilized to carry out the development of an embryo, this is known as parthenogenesis, an event that will give rise to offspring genetically exact to the mother. This last case can be seen in some species of geckos, such as the spiny lizard (Heteronotia binoei) and in a species of monitor lizards, the peculiar Komodo dragon (Varanus komodoensis).
Another way to consider the types of reproduction in reptiles is whether fertilization is internal or external. In the case of reptiles, there is always internal fertilization Males have a reproductive organ known as a hemipenis, which usually varies from one species to another, but is found inside the animal and, as in the case of mammals, it emerges or erects at the time of copulation, in this way, the male introduces it into the female to fertilize her.
Examples of reptiles and their reproduction
Now let's see some examples of the different types of reproduction of reptiles:
- Oviparous reptiles: Some snakes, such as pythons, lizards such as the Komodo dragon, turtles, and crocodiles.
- Ovoviviparous reptiles: a type of chameleon, such as the species Trioceros jacksonii, the snakes of the genus Crotalus, known as the rattlesnake, the viper asp (Vipera aspis) and a legless lizard known as the lucion (A nguis fragilis).
- Viviparous reptiles: some snakes, such as boas and certain lizards, such as the species Chalcides striatus, commonly known as the Iberian three-toed skink and lizards of the genus Mabuya.
The reproduction of reptiles is a fascinating area, given the variants that exist in the group, which are not restricted to the reproductive types mentioned above, but exist other variations, as is the case of species that, depending on the area where they are located, can be oviparous or viviparous. An example of these is found in the bog lizard (Zootoca vivipara), which reproduces oviparously in the Iberian populations located in the extreme west, while those existing in France, the British Isles, Scandinavia, Russia and part of Asia, it does so viviparously. The same is true of two species of Australian lizards, Lerista bougainvilli and Saiphos equallis, which display different reproductive modes depending on location
Reptiles, like other animals, never cease to amaze us with their many adaptive forms that seek to give continuity to the species that make up this group of vertebrates.
