Vivipary

Viviparous (Latin viviparus viviparous, ovoviviparous ' ) denotes the propagation manner in animals from which embryonic development proceeds in mother animal, without being surrounded by an egg case. In plants, it refers to the embryonic development of the mother plant.

Animals

In animals, viviparity is in contrast to oviparity, so oviposition, after taking place the embryo in the egg for the most part outside the mother. When Viviparie the juveniles remain throughout their embryonic development in the womb.

A clear demarcation to Ovoviviparie, are hatched in the yolk- rich Nähreier in the womb and the embryos are nourished only by the nutrients stored in the yolk sac of the egg is difficult. Often the Ovoviviparie is equated with aplazentaler viviparity and viviparity with placental viviparity, but this is not correct: The embryos viviparer animals are on the circulation of the mother animal supplies (nutrients, respiratory gases, excretion, water), which does not necessarily require a placenta. The following options for the supply of the embryo in the womb are known:

• In all higher mammals ( Eutheria ) and some bags mammalian placenta is formed. But also at various skinks and snakes, there are some placenta formation, in which the allantois and the chorion of the embryo and unite snugly to the uterine mucous membrane of the mother. In some lizards ( Lacertilia ), certain tissue layers, the mother and the embryo separate, reduced until there is contact of endothelial cells of the embryo and the mother, who is regarded as placental formation. For most basic sharks closely connected to the fallopian tubes, pleated yolk sac forms a yolk sac placenta. Even with some Zahnkärpflingen it comes to placental defects. Occasionally you can find for all placental viviparous animals the term placental mammals, but which should be a taxonomic group, namely the mammalian subclass Eutheria are reserved, even if he is elected as unfortunate for them because just train some marsupial placenta. In order not to increase the confusion, it should be avoided as a collective term for unrelated groups with the same Embryonalversorgung.
• One way of aplazentalen supply of the embryo is the removal of a Nährsekretes in the uterus. This " uterine milk " is mixed with leukocytes and tissue residues. It can be taken directly from the embryos or to be transported in the intestine of the embryo via secretion villi through the spray hole ( with rays) or the gills with genuine bony fish ( Teleostei ). Also, the embryo can appendages for the purpose of diet form ( trophotaenia ) such as in the Hochlandkärpflingen ( Goodeidae ). Other representatives of the Zahnkärpflinge have developed more diets, especially those whose development takes place in the ovary.
• Another form of nutrition of the embryo is called the " intrauterine cannibalism " or Oophagie. It develop from the eggs in the oviduct or in the womb, only a few or only one, the other will crumble to a Nährbrei or from or the remaining embryos eaten. This form can be found among others in some groupers ( Perciformes ) in Makrelenhaiartigen ( Lamniformes ) or the Alpine salamander.

As they develop the young viviparer species during their embryonic development in the narrow unborn, these types have to be oviparous compared usually fewer offspring and are thus within the meaning of the reproductive strategy of K- strategists. The oldest fossil evidence of live childbirth is 380-375 million years old discovery of a associated with an umbilical cord to the mother embryo of the Upper Devonian armored fish Materpiscis ( Long et al. 2008).

Plant

In botany, the term viviparous is used to refer to reproductive forms in which the seedling remains on the parent plant, and certain forms of vegetative propagation, when genetically identical daughter plants produced from the flower primordia. Examples of viviparity in the plant kingdom are bluegrasses as Poa vivipara ( South Africa) and Poa alpina ssp. vivipara (occurrence in the Alps), also observed in the foxtail grasses.

Swell

• Erwin Hentschel, Günther Wagner Zoological Dictionary, Gustav Fischer Verlag, Jena, 1990, ISBN 3-334-00348-5 4th edition.
• Adolf Remane, Volker Storch, Ulrich Welsch: Short Textbook of Zoology, Stuttgart and New York: Fischer, 1989.6. Edition. ISBN 3-334-00333-7
• Hans -Günter Petzold: tasks and problems in the study of the expression of life in the Low amniotes. MILU 5 (4/ 5): 485-786 ( Berlin Tierpark Book 38)
• Lothar fights, Rolf gown, John Klapper piece: Guide to the anatomy of vertebrates, Gustav Fischer Verlag, Jena, 1987, ISBN 3-334-00082-6 5th edition

• Reproduction