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

animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...

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

amphibian 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, arbo ...

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 t ...

'', are born as

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

e, 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 ''Nectophrynoides'' is a genus of true toads, family Bufonidae. They are endemic to Eastern Arc forests and wetlands in Tanzania,Channing and Howell. (2006). ''Amphibians of East Africa.'' Pp. 104–117. and all except '' N. tornieri'' are thr ...

'' and ''

Eleutherodactylus ''Eleutherodactylus'' is a genus of frogs in the family Eleutherodactylidae.Hedges, S. B., W. E. Duellman, and M. P. Heinicke . 2008. New World direct-developing frogs (Anura: Terrarana): molecular phylogeny, classification, biogeography, and c ...

'' 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 Opportunism is the practice of taking advantage of circumstances – with little regard for principles or with what the consequences are for others. Opportunist actions are expedient actions guided primarily by self-interested motives. The term ...

exploitation of transient food sources, such as many

Sarcophagidae Sarcophagidae () are a family of flies commonly known as flesh flies. They differ from most flies in that they are ovoviviparous, opportunistically depositing hatched or hatching maggots instead of eggs on carrion, dung, decaying material, or o ...

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 ...

flies, and species such as many

Calliphoridae The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ba ...

, 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 The Tachinidae are a large and variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in this family ...

flies that depend on entering the host as soon as possible, the embryos commonly develop to the first larval

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

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 Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For inte ...

and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does provide

gas exchange Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a ...

. 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 Matrotrophy is a form of maternal care during organism development, associated with live birth (viviparity), in which the embryo of an animal or flowering plant is supplied with additional nutrition from the mother (e.g. through a placenta). This ...

, in which the embryo exhausts its yolk supply early in gestation and the mother provides additional nutrition. This additional provisioning may be in the form of unfertilized eggs (intrauterine oophagy), uterine secretions (

histotrophy Histotrophy is a form of matrotrophy exhibited by some live-bearing sharks and rays, in which the developing embryo receives additional nutrition from its mother in the form of uterine secretions, known as histotroph (or "uterine milk"). It is on ...

) 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 are sometimes born as

e, and undergo metamorphosis outside the body of the mother. Modes of reproduction include based on relations between

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

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''. In seahorses, zygotes remain in the male's ventral "marsupium". In the frog '' Rhinoderma darwinii'', the zygotes develop in the vocal sac. In the frog '' Rheobatrachus'', zygotes develop in the stomach.

Ovolarviparity

Some insects, notably

tachinid flies The Tachinidae are a large and variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in this family ...

, are ovolarviparous, which means that the embryos develop into the first larval stage (

) within the eggs while still in the female's

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...

. 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