Most reptiles lay eggs that hatch outside their body, a process known as ovipary. But some, such as lizards and snakes, give birth to live young.
To mate, a male reptile inserts either his single penis or one of two hemipenes into a female’s cloaca. Herps don’t have external genitalia to help owners determine their sex, but males can be distinguished by their larger head and general body size.
Reptiles can be oviparous (lizards, geckos and tortoises), viviparous (skinks) or ovoviviparous (boas). In some species of reptiles, including certain geckos, pythons, rock lizards, monitor lizards and brahminy blind snakes, females reproduce through parthenogenesis. In this form of reproduction, eggs are self-activated and do not require sperm to be fertilized. This results in offspring that have the same chromosomes as their m 파충류샵 other.
Male reptiles possess paired testes, but they do not have a penis like mammals. Instead, sperm is discharged through a cloacal opening. After a male and a female copulate, the sperm is then passed up through each of the female’s oviducts until it reaches an opening adjacent to one of her eggs.
The oviducts of some species of turtles also have the ability to store sperm until the eggs are ready to be ovulated. This is known as vivipary. In this case, the male lays his sperm in the female’s oviducts and she then guards them from predators until they hatch.
In a number of reptiles, particularly pythons and boa constrictors, the process of fertilization is more complex because the oviducts are lined with an individual membrane that protects each egg. This makes the process more reliant on a precise time of day, enclosure design and diet to ensure that follicles are mature. In these cases, ovulation occurs in response to the release of luteinizing hormone (LH) from the corpus luteum.
Reptiles are oviparous and lay eggs that hatch in the external environment. However, some snake and lizard species, like the boas, vipers, and pythons, are viviparous and give birth to live young instead of eggs.
When the time comes for fertilization, male reptiles insert sperm from their cloaca into the female’s oviduct. A typical male reptile has a single penis (turtles and crocodiles) or two hemipenes that are homologous to a mammalian penis.
Once sperm has entered the female’s oviduct, it moves up to an opening adjacent to one of her eggs and fertilizes it. Fertilization may occur within an hour of ovulation, within a week, or even months before. The female’s ovulation is stimulated by copulation but can also be triggered by hormones secreted by the corpus luteum or from her having eaten.
When the egg is fertilized, it encloses itself in an amniotic sac that is covered by a layer of a sticky liquid called allantois. Allantois is similar to the fluid found in a mother’s womb and serves to protect the embryo, facilitate the transfer of nutrients, and help remove metabolic waste. It is also a source of calcium for the developing embryo and contains fats that are used as energy by the embryo. Gestation can last from several weeks to over six years in some reptile species.
Unlike mammals, who give birth to live offspring, most reptiles lay eggs. They may place these eggs in nests, or they may hold the embryos in their mouths until they hatch. In either case, the eggs contain a rich source of nutrients. Reptile eggs are protected by extra-embryonic membranes (the amnion and allantois) and a hard, calciferous shell.
During sexual reproduction, males deposit sperm directly into the female’s reproductive tract. This is called cloacal apposition, and it takes place either during mating or by the use of an intromittent organ in certain species of reptiles, such as the tuatara (Sphenodon). In other reptiles, males have one or two penises that discharge sperm into the opening of the female’s cloaca. The sperm enters her eggs and fertilizes them. The fertilized eggs then leave the female through her cloaca.
A major evolutionary advance in reptile reproduction was the evolution of internal fertilization, which allowed for the development of a large, protective egg. This in turn facilitated the evolution of a solid, terrestrial body, and it also enabled vertebrates to become fully land-based. Interestingly, some reptiles that lay eggs can also bear live young, and these are known as viviparous. The Australian three-toed skink is one such reptile. This reptile produces offspring that are genetically identical to its mother through a process called parthenogenesis.
Most reptiles are oviparous, which means that they lay eggs that hatch outside their body. Some, however, give birth to live young. This is called viviparous reproduction and it’s seen in snakes, lizards, and turtles. Those that are viviparous have an advantage over egg-laying reptiles: their offspring get their nutrition from the egg yolk instead of through a placenta.
During copulation, male reptiles have one or two penises that transfer sperm into the female’s cloaca, which is like her uterus. From there, fertilization occurs. Afterwards, the female may keep her sperm stored up for a period of time, which can be up to six years. This allows the sperm to fertilize succeeding eggs without any more male contact.
Some reptile species have a feature that allows them to switch between egg-laying and viviparity depending on the season and ecological conditions. This is called temperature-dependent sex determination and all crocodiles, some turtles, tuatara, and some lizards have this trait.
In addition to being able to switch between viviparous and oviparous reproduction, many reptiles are precocial. This means that they are born fully physically capable and can fend for themselves from the start. This is important because it helps to reduce the amount of energy that a mother needs to expend on nurturing her offspring. This can also allow reptiles to reproduce in environments where food and shelter are limited.