Magnitude and significance of the peak of early embryonic mortality
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Magnitude and significance of the peak of early embryonic mortality Qinghua Chen 1 & Zengru Di 1 & Eduardo M. García Roger 2 Peter Richmond 3 & Bertrand M. Roehner 4
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& Hui Li &
Received: 10 June 2020 / Accepted: 7 August 2020 / Published online: 17 August 2020 # Springer Nature B.V. 2020
Abstract
Embryonic development is of great importance because it determines congenital anomalies and influences their severity. However, little is known about the actual probabilities of success or failure and about the nature of early embryonic defects. Here, we propose that the analysis of embryonic mortality as a function of post-fertilization time provides a simple way to identify major defects. By reviewing the literature, we show that even small initial defects, e.g., spatial cellular asymmetries or irregularities in the timing of development, carry with them lethal effects in subsequent stages of embryogenesis. Although initially motivated by human study, in this contribution, we review the few embryonic mortality data available for farm animals and highlight zebrafish as a particularly suited organism for such a kind of study because embryogenesis can be followed from its very beginning and observed easily thanks to eggshell transparency. In line with the few other farm animals for which data are available, we provide empirical evidence that embryonic mortality in zebrafish has a prominent peak shortly after fertilization. Indeed, we show how subsequent mortality rates decay according to a power law, supporting the role of the early embryonic mortality peak as a screening process rapidly removing defective embryos. Keywords Embryogenesis . Death rate . Post-fertilization age . Screening . Zebrafish
1 Introduction The process by which any organism develops from a single-celled zygote to a multicellular organism is complex and therefore prone to error. Thus, embryonic development is of great importance because it determines congenital anomalies and influences their severity, and so it is crucial for ensuring the fitness of the organism. Whereas there is detailed qualitative knowledge of the successive steps of embryonic development, little is known about their * Eduardo M. García Roger [email protected] Extended author information available on the last page of the article
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probabilities of success or failure. However, and despite the lack of accurate data, it is in general accepted that natural mortality occurring during the early embryonic development may be high, as recognized in humans [1], in what is called the early embryonic mortality (hereafter, EEM) effect. Far from being specific to humans, EEM seems to exist for all other species for which data are available [2, 3]. However, it is fair to acknowledge that very limited data on such early spikes of mortality are available so far (see below in section 2, entitled “Embryonic mortality in farm and laboratory animals”), and that the literature gives us almost no real clues for understanding the EEM effect. That is why we think it may be enli
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