Reptiles have two main reproductive strategies: those that lay eggs and those that birth live young. The latter are known as viviparous.
When oviparous reptiles mate, the male’s penis (often one but sometimes two) passes sperm into the female’s cloaca for internal fertilization.
Some viviparous reptiles, such as crocodiles, turtles, tortoises, snakes and lizards, deliver live offspring by laying eggs. Other species, such as three-toed skinks, give birth to asexual offspring.
Oviparous
Oviparous animals produce eggs that hatch outside of the mother. Examples include birds, reptiles, amphibians, and fish. Viviparous animals, on the other hand, give birth to live young. These animals are called ovoviviparous, or aplacental viviparous. This type of reproduction is more common 도마뱀분양 in reptiles and amphibians than in mammals.
Viviparous evolution has been associated with a variety of adaptations in morphology, physiology, and ecology (Seymour et al., 1995). These adaptations may include increased female locomotion ability resulting from reduced space constraints of a maternal nest, protection from adverse environmental conditions and predation pressures, and larger offspring size at independence, which can enhance survival. However, these advantages have also led to decreased reproductive output and increased female mortality (Qualls and Shine, 1995; Goodwin et al., 2002).
The reproductive mode of an individual is a Mendelian character that can be inherited from parents. It is possible that hybrids between oviparous and viviparous individuals can exhibit intermediate characteristics, such as eggshell regression and earlier embryonic development at the time of laying. Moreover, the eggs of these hybrids may be smaller than those of oviparous animals and their incubation period shorter. However, more research is needed on F2 hybrids to determine if this is true. This will help to confirm whether the reproductive mode of an individual behaves as a dominant or recessive character. 도마뱀분양
Vividiparous
In viviparous animals, nutrients are transferred from the mother directly to her embryos. Some reptiles that are viviparous include snakes, lizards and fish. Others are ovoviviparous, in which eggs are stored in the female’s oviducts until they are fertilized. Marsupials are another type of ovoviviparous animal, which gives birth to live young. Viviparous species typically have large litters, which are born alive and are able to move around after birth. This type of reproductive mode is adapted to a variety of habitats, and it can reduce the time spent by mothers nursing their young.
In contrast, oviparous common lizards tend to have smaller litters and require more time to nurse. Several studies have found that offspring from viviparous females are less well-fed than those from oviparous females (Horvathova et al. 2013). These differences in offspring size and survival may be related to the greater parental investment required for viviparous reproduction. Interestingly, viviparous and oviparous offspring of the same lizards are genetically distinct to the subspecies level (Horreo et al. 2019).
In addition to being more physically larger, viviparous females also produce more offspring than their oviparous counterparts. This suggests that a larger body size is an important selective advantage for the evolution of viviparous reproductive strategies. However, this relationship must be evaluated at a finer scale to ensure that it is not confounded by other factors.
Gravid
This type of reptile reproduces by laying eggs inside its proglottids. The ovum is an oval or round structure that contains 3 membranes. The outer mammilated albuminous sticky membrane is followed by two internal smooth membranes. These are then surrounded by granular material that gives rise to larvae when the egg hatches. The ovum is passed in the feces and can be detected by examining the fecal contents of Ascariasis.
The gravid female can produce up to 200,000 ova per day. Ovulation can be detected in the feces of the female as small, brown, and round. These ova are fertilized by sperm in the uterus of the male. When fertilized, they grow into an embryo. The embryo then implants into the uterus and develops into a gravid lizard. The oviposition process takes about a month, but it can take as long as a year for the gravid female to reach maturity.
Studies of morphological and locomotor data have shown that the occurrence of pregnancy reduces a lizard’s running speed by about 18%. The reduction in speed is due to a combination of factors, including body temperature, feeding state and tail-autotomy. However, it is not clear how the different factors interact to produce this effect. This finding may explain why vivipary is more common in tropical than temperate-zone habitats, despite the lower benefits of surviving prolonged retention of eggs.
Eggs
Reptiles are well known for laying eggs, but they also give birth to live young. Some lizards and snakes are ovoviviparous, which means they retain the embryo inside their bodies until it is ready to hatch. Others are viviparous and give birth to live offspring like mammals. These two different reproductive strategies serve a variety of purposes for reptiles.
The egg is an important invention in reptilian evolution. It allows reptiles to reproduce away from water, which would otherwise be necessary for a successful pregnancy. The shell protects the developing embryo from drying out and provides a nutritious environment for the fetus. The egg is rubbery and has a specialized membrane that allows for the development of the fertilized embryo to take place within.
In oviparous reptiles, the male and female have specialized sexual organs for fertilization. The male has paired testes and the female has a right and left oviduct without a true uterus. During mating, the male ejaculates semen into the cloaca of the female’s body cavity and this enters her ovary to be fertilized with sperm.
During this process, the ovoviviparous reptiles have a special advantage in that they can preserve sperm from their copulation for up to six years. This allows the sperm to fertilize succeeding eggs even when there is no more contact between the male and female. It is likely that this is why ovoviviparous reptiles are able to produce clutches of eggs in the same year that they mate.