Oviparity

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Tau emerald dragonflies mating. Sperm is transferred externally; dragonflies lay fertilised eggs on plants in or near water.

Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, reptiles, all birds, and the monotremes.

In traditional usage, most insects, molluscs, and arachnids are also described as oviparous; Thierry Lodé (2012), however, describes the mode of reproduction in these organisms as "ovuliparous".[1]

Modes of reproduction[edit]

Main article: modes of reproduction

The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or fertilised eggs are spawned, and viviparity traditionally including any mechanism where young are born live, or where the development of the young is supported by either parent in or on any part of their body.[1]

The biologist Thierry Lodé divided the traditional oviparous mode of reproduction based on the relationship between the zygote (fertilised egg) and the parents into two modes, one of them named (true) oviparity:[2][1]

  • (True) oviparity: fertilisation is internal, but the female lays zygotes as eggs with a substantial quantity of yolk to feed the embryo while it remains in the egg. The egg is not retained in the body, or only for a limited time.[1] Oviparity is found in birds. Among mammals, the monotremes (four species of Echidna, and the Platypus) are oviparous.

Thus the definition of oviparity is narrower in the revised scheme, as it does not include the "ovuliparity" found in most fish, most frogs and many invertebrates.

References[edit]

  1. ^ a b c d e f Lode, Thierry (2012). "Oviparity or viviparity? That is the question ...". Reproductive Biology 12: 259–264. doi:10.1016/j.repbio.2012.09.001. 
  2. ^ Thierry Lodé (2001). Les stratégies de reproduction des animaux (Reproduction Strategies in Animal Kingdom). Eds. Dunod Sciences. Paris.

External links[edit]