Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s that develop inside

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

s that remain in the mother's body until they are ready to hatch. The young of some ovoviviparous

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

s, such as ''

Limnonectes larvaepartus ''Limnonectes larvaepartus'' is a species of fanged frog in the family Dicroglossidae endemic to northern and western Sulawesi, Indonesia. It is unique in that it has internal fertilization and gives live birth to tadpoles. Other frog species ...

'', are born as larvae, and undergo further

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

outside the body of the mother. Members of genera '' Nectophrynoides'' and '' Eleutherodactylus'' bear froglets, not only the hatching, but all the most conspicuous

, being completed inside the body of the mother before birth. Among insects that depend on opportunistic exploitation of transient food sources, such as many Sarcophagidae and other

carrion Carrion () is the decaying flesh of dead animals, including human flesh. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...

flies, and species such as many Calliphoridae, that rely on fresh dung, and

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s such as tachinid flies that depend on entering the host as soon as possible, the embryos commonly develop to the first larval instar inside the mother's reproductive tract, and they hatch just before being laid or almost immediately afterwards.

Ovoviviparity

Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by

egg yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

; the mother's body does provide gas exchange. In some species, the internally developing embryos rely solely on yolk. This is known as "yolk-sac viviparity" and is regarded as a type of lecithotrophy (no maternal provisioning). Other species exhibit matrotrophy, in which the embryo exhausts its yolk supply early in

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...

and the mother provides additional nutrition. This additional provisioning may be in the form of unfertilized eggs (intrauterine oophagy), uterine secretions ( histotrophy) or it may be delivered through a placenta. The first two of these modes were categorized under histotroph viviparity, or aplacental viviparity.

Amphibians

The young of ovoviviparous

amphibians Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...

are sometimes born as larvae, and undergo

outside the body of the mother. Modes of reproduction include based on relations between zygote and parents: * Ovuliparity: external fertilisation, as in arthropods, many bony fishes, and most amphibians * Oviparity: internal fertilisation, where the female lays zygotes as eggs with important vitellus (typically birds) * Ovo-viviparity can be thought of as a form of oviparity where the zygotes are retained in the female's body or in the male's body, but there are no trophic interactions between zygote and parents. This is found in ''

Anguis fragilis The slow worm (''Anguis fragilis'') is a reptile native to western Eurasia. It is also called a deaf adder, a slowworm, a blindworm, or regionally, a long-cripple and hazelworm. These legless lizards are also sometimes called common slowworms. Th ...

''. In seahorses, zygotes remain in the male's ventral "marsupium". In the frog ''

Rhinoderma darwinii Darwin’s frog (''Rhinoderma darwinii''), also called the Southern Darwin's frog, is a species of Chilean/Argentinian frog of the family Rhinodermatidae. It was discovered by Charles Darwin during his voyage on voyage on HMS ''Beagle''. on a ...

'', the zygotes develop in the vocal sac. In the frog ''

Rheobatrachus The gastric-brooding frogs or platypus frogs (''Rheobatrachus'') is a genus of extinct ground-dwelling frogs native to Queensland in eastern Australia. The genus consisted of only two species, both of which became extinct in the mid-1980s. The g ...

'', zygotes develop in the stomach.

Ovolarviparity

Some insects, notably tachinid flies, are ovolarviparous, which means that the embryos develop into the first larval stage ( instar) within the eggs while still in the female's oviduct. As a result, the larvae hatch more rapidly, sometimes immediately after egg deposition, and can begin feeding right away. A similar phenomenon is larviparity, in which larvae hatch ''before'' the female delivers them, although this may be mistakenly identified in species with very thin and transparent egg membranes.

Criticisms and disuse

A lack of a rigidly defined term resulted in widespread misuse of the term ovoviviparity in the biological literature. Ovoviviparity has been used to describe delayed forms of egg-laying reproduction as well as live-bearing species that provide maternal nutrients but do not use a placenta. This widespread misuse of the term has led to confusion over what earlier authors meant when using the name. Modern practice has seen the disuse of ovoviviparity in favour of the more specific definitions of lecithotrophic and matrotrophic oviparity and viviparity.

References

{{Portal bar, Sharks, Gastropods, Snakes, Frogs, Amphibians, Fish Reproduction in animals Live-bearing fish Ovoviviparous fish Articles containing video clips