Generally, most reptiles reproduce sexually and exhibit internal fertilization. Males have one or two penises that transport sperm from their cloaca to the cloaca of a female. In a few species, the eggs are retained inside the female’s body until they hatch. Then the offspring escape from the mother’s body through the cloaca opening. In reptiles, the offspring develops inside the female and is born alive.
This takes place in some cartilaginous fishes, mostly in mammals and a few species of reptiles. Internal fertilization protects the fertilized egg from dehydration on land. Mostly reptiles lay eggs, while mammals give birth to their offspring. It is found that lizards and snakes first evolved live birth approximately 175 million years ago. Many reptiles lay flexible, calcified eggshells.
Some of them may lay hard eggs. On the other hand turtles and tortoises lay hard or soft eggs depending on the types of their species. Both reptiles and amphibians come from eggs, but amphibians require to stay in moist or wet places as they develop. While reptiles need to stay in dry places, and they eggs on land, often burying them.
The common lizard (the viviparous lizard) is a Eurasian lizard. These are non-marine reptiles. Most populations are viviparous (giving birth to live young) rather than laying eggs as other most lizards do. Crocodiles and turtles produce some of the largest clutches among the living reptiles, sea turtles sometimes produce more than 100 eggs each time, while larger crocodiles average 40 to 50 per clutch.
The minerals in the shells of reptiles’ egg can make them harder, although most reptiles lay eggs with leathery, soft shells. Some types of turtles and crocodilians lay eggs with hard or tough shells, more like a bird’s egg.
Unlike fishes and amphibians, reptiles produce amniotic eggs. The shell, membrane, and other material of an amniotic egg nourish and protect the embryo. They keep the embryo safe and moist while it grows and develops. Actually, the amniotic egg was evolutionary that allowed the reptiles to colonize dry land more than 300 million years ago.
Reptiles that give live birth to their young
There are three major groups of reptiles: lepidosaurs (lizards and snakes), crocodiles and turtles. Of the three, live birth is only observed in lepidosaurs. Reptiles that give birth to their offspring can be divided into 2 categories, viviparous and ovoviviparous.
Viviparous Snakes and Lizards
Amongst all the reptiles viviparity is more common in snakes. From sea snakes to garter snakes, viviparous snakes live in different ecosystems. Besides snakes, there are only two kinds of leg-less reptiles called skins, viviparous lizards, and night lizards, a group of enigmatic lizards found in Central America and the southwestern US.
Ovoviviparous reptiles live in the United Kingdom. Ovoviviparous exist between viviparous and oviparous: they lay and do give birth to their young. There are some species for example vipers and rattlesnakes that are ovoviviparous, in these types of snakes eggs remain inside the body after fertilization until it can hatch. Similarly, the antenatal anaconda is ovoviviparous that is found in the swamps of northern Argentina. When a female snake (anaconda) has young snakes inside her, she must regulate the ideal internal temperature. She will give birth to anywhere between 15 and 40 young, each snake kid is totally independent after birth.
Breeding Behavior in Snakes
Female snakes escape from hibernation in the spring season to mate. We know that snakes are cold-blooded vertebrates, they cannot regulate their body temperature. They prefer warmer conditions for breeding as well as egg-laying. Upon mating, females start to search for safe locations to lay their eggs, such as beneath leaves or underground.
Within the snake family, a male snake tries his best to get the female to open her cloaca in order to insert his penis and mate with her. When a locks onto the pheromone scent of a female receptive to mating, he will follow until he finds her.
Some snakes may steal eggs from snakes or other organisms by swallowing them, while some lizards lay eggs and others give live birth.
Do reptiles reproduce asexually?
Parthenogenesis is a way of asexual reproduction, in which the offspring are produced by females without the genetic combination of the males. It is estimated that there are around 50 species of lizard and 1 species of snake that reproduce alone by means of parthenogenesis.
The births given by means of parthenogenesis are commonly termed virgin births. In certain conditions, it is possible for a female to keep the male sperm in her cloaca for a period of up to 6 years. Even a female bearded dragon that lives alone can lay eggs, the reason is that it recently spent time with a male dragon or simply it is not uncommon for female bearded dragons and other types of animals to lay infertile eggs without ever having with a male.
As with all types of asexual reproduction, there are both costs and benefits related to parthenogenesis. The offspring produced by parthenogenesis are always female in species where the sex of the offspring is determined by the sperm (XY chromosome system), and they are male in species where the sex of the offspring is determined by the egg (as in the ZW chromosome system).
Most mammals have the XY chromosome system. XX individuals are female, and XY individuals are male. On the other hand some organisms, such as butterflies and birds, have the ZW chromosome system. ZW individuals are female, and ZZ is male. In some reptiles sex can also be determined by the environment; for example, the sex of turtles and crocodilians are dependent on the incubation temperatures of the eggs.
In some species of squamates, a population of females is able to produce a unisexual diploid clone of the female (mother). This is also a type of parthenogenesis, that takes place in many different species of geckos (small lizards found in warm climates throughout the world. Their size range from 1.6 to 60cm) and is particularly widespread in the teiids. Some Komodo dragons (Varanidae) may also reproduce by parthenogenesis.