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'' and ''
Eleutherodactylus'' bear froglets, not only the hatching, but all the most conspicuous
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 ...
, 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 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
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
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
species in which there is
internal fertilization and the young are born alive, but differ in that there is no
placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...
l 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
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 ...
. 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 pr ...
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 placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...
. The first two of these modes were categorized under histotroph
viviparity
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
, or aplacental viviparity.
Amphibians
The young of ovoviviparous
amphibians are sometimes 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
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.
Modes of reproduction
Animals make use of a variety of modes of reproduction to produce their young. Traditionally this variety was classified into three modes, oviparity (embryos in eggs), viviparity (young born live), and ovoviviparity (intermediate between the first ...
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
amphibia
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 ...
ns
* 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
seahorse
A seahorse (also written ''sea-horse'' and ''sea horse'') is any of 46 species of small marine fish in the genus ''Hippocampus''. "Hippocampus" comes from the Ancient Greek (), itself from () meaning "horse" and () meaning "sea monster" or ...
s, zygotes remain in the male's ventral "marsupium". In the frog ''
Rhinoderma darwinii'', 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 ...
'', 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
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 ...
) 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
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