Postembryonic Development

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Postembryonic Development

 

the period in the ontogenesis of multicellular animals that follows the period of embryonic development and usually ends with the onset of sexual maturity and, in most animals, the cessation of growth. Postembryonic development begins after the emergence of the embryo from the egg and embryonic membranes, when the organism becomes capable of active feeding and locomotion. Upon transition to the postembryonic state the organism either immediately possesses the principal pubertal morphological characteristics (direct development) or essentially differs from the pubertal form, in which case the larva that hatches out of the egg must undergo a metamorphosis before it reaches its adult state. Growth continues during the period of postembryonic development and further organogenesis and histogenesis occur. The functions of the developing organism become more complex; establishment of the final proportions of the body is especially characteristic.

In some animals postembryonic development constitutes the greater part of their life span. Among insects, in a number of cicadas the larva lives 17 years, while the pubertal insect lives one summer; the mayfly larva lives to three years, but often in its pubertal form the mayfly lives only one day.

The necessity for defense against enemies and active food procurement are ensured during postembryonic development by a number of adaptations that make the animal self-sufficient, sometimes for its entire life span. With indirect, or larval, development, the animal, having larval organs, is self-sufficient only during the postembryonic period.

A. V. IVANOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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Postembryonic development of the cephalic skeleton in Dicentrarchus labrax (Pisces, Perciformes, Serranidae).
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Although postembryonic development of relatively few species have been studied, cosmetid harvestmen have been observed to have six nymphal instars before the final molt to adulthood (Juberthie 1972; Goodnight & Goodnight 1976).
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While a third case has alluded to this particular complication, it has been disregarded by previous scholarly journals as "confirmed [6]." Bleeding, similar to the previous cases [4, 5], was found to originate from the artery of Sampson, a vessel which is normally obliterated in postembryonic development but which can persist as a branch of the uterine artery that runs along the length of the uterine round ligament in adult females.
[15] improved the mature postembryonic development of SEs of Picea glauca x P engelmannii by gradually lowering the high relative humidity to achieve partial desiccation, which decreased the germination time, synchronized stem and root development, and resulted in >90% conversion frequency.
The first phase covers the planktonic period of postembryonic development, and the second period represents benthic life.