Ovoviviparity
Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos that develop inside eggs remain in the mother's body until they are ready to hatch. This method of reproduction is similar to viviparity but the embryos have no placental connection with the mother but receive their nourishment from a yolk sac. In some species, this is supplemented by uterine secretions or other maternal provisioning.
The young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother, and in some insect species, such as the tachinid flies, the embryos develop to the first larval instar stage before they are laid and the eggs hatch almost immediately.
Ovoviviparity
Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born live, 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 (sharks and rays). The terms "ovoviviparity" or "aplacental viviparity" have been deprecated because they encompass several unrelated modes of reproduction.[1]
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 and 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 aplacental viviparity.[2]
Amphibians
The young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother. Modes of reproduction include[3] 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. 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.[4]
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.[5][6]
References
- ↑ Blackburn, D. G. (2000). Classification of the reproductive patterns of amniotes.:" Herpetological Monographs", 371-377.
- ↑ Carrier, J.C.; Musick, J.A.; Heithaus, M.R., ed. (2012). Biology of Sharks and Their Relatives. CRC Press. pp. 296–301. ISBN 1439839247.
- ↑ Thierry Lodé 2001. Les stratégies de reproduction des animaux (reproduction strategies in animal kingdom). Eds Dunod Sciences, Paris
- ↑ Tyler, M. J. (1994). Australian Frogs: A Natural History. Chapter 12, Gastric Brooding Frogs pp;135–140 Reed Books
- ↑ Capinera, John L. (2008). "Tachinid Flies (Diptera: Tachinidae)". Encyclopedia of entomology (2nd ed.). Dordrecht: Springer. pp. 3678–3679. ISBN 9781402062421.
- ↑ Wiman, Nik G.; Jones, Vincent P. (2012). "Influence of oviposition strategy of Nemorilla pyste and Nilea erecta (Diptera: Tachinidae) on parasitoid fertility and host mortality" (PDF). Biological Control 64 (3): 195–202. doi:10.1016/j.biocontrol.2012.12.008.
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