Phenotypic Switching Resulting From Developmental Plasticity: Fixed or Reversible?

Abstract

The prevalent view of developmental phenotypic switching holds that phenotype modifications occurring during critical windows of development are "irreversible"that is, once produced by environmental perturbation, the consequent juvenile and/or adult phenotypes are indelibly modified. Certainly, many such changes appear to be non-reversible later in life. Yet, whether animals with switched phenotypes during early development are unable to return to a normal range of adult phenotypes, or whether they do not experience the specific environmental conditions necessary for them to switch back to the normal range of adult phenotypes, remains an open question. Moreover, developmental critical windows are typically brief, early periods punctuating a much longer period of overall development. This leaves open additional developmental time for reversal (correction) of a switched phenotype resulting from an adverse environment early in development. Such reversal could occur from right after the critical window "closes," all the way into adulthood. In fact, examples abound of the capacity to return to normal adult phenotypes following phenotypic changes enabled by earlier developmental plasticity. Such examples include cold tolerance in the fruit fly, developmental switching of mouth formation in a nematode, organization of the spinal cord of larval zebrafish, camouflage pigmentation formation in larval newts, respiratory chemosensitivity in frogs, temperature-metabolism relations in turtles, development of vascular smooth muscle and kidney tissue in mammals, hatching/birth weight in numerous vertebrates,. More extreme cases of actual reversal (not just correction) occur in invertebrates (e.g., hydrozoans, barnacles) that actually 'backtrack' along normal developmental trajectories from adults back to earlier developmental stages. While developmental phenotypic switching is often viewed as a permanent deviation from the normal range of developmental plans, the concept of developmental phenotypic switching should be expanded to include sufficient plasticity allowing subsequent correction resulting in the normal adult phenotype.

What do warming waters mean for fish physiology and fisheries?

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Stress and odorant receptor feedback during a critical period after hatching regulates olfactory sensory neuron differentiation in Drosophila

“…The restricted duration of OR expression maturation suggests that the period of gene regulation plasticity may be a bona fide critical period [ 50 , 51 ]. OR regulation does fulfill the criteria.…”

Survival, Growth, and Development in the Early Stages of the Tropical Gar Atractosteus tropicus: Developmental Critical Windows and the Influence of Temperature, Salinity, and Oxygen Availability

“…Developmental phenotypic plasticity is the ability of an organism in its early stages to modify its phenotype as a function of intrinsic (genetic) or extrinsic (environmental) factors [1][2][3]. Modifications in the developmental trajectory as a result of phenotypic plasticity have the capacity to alter traits in adulthood, being either adaptative or detrimental [4][5][6].…”