Shape: Its development and regulation capacity during embryogenesis

Abstract

Although several theoretical approaches consider general methods for dealing with shape, recent observations and experimental data show that embryos exhibit marked changes in the properties of the biological material involved in shape development and shape regulation capacity. In vivo experiments have shown that the amphibian embryo gradually develops from a situation in which it is not able to maintain its shape to one in which it can not only maintain its shape but also possesses a maximal tolerance towards deformation together with a maximal shape regulation capacity. So far two especially clear conclusions have emerged: (i) the form of the embryo appears to be determined by cell activities intrinsic to each stage, and (ii) the morphogenetic programme can be executed normally within wide limits notwithstanding dramatic deformations of the embryo during quite a long period. Thus the hypothesis may be advanced that shape and morphogenesis to some extent become independent phenomena during embryonic development.

Sublethal effects of atrazine on embryo-larval development of Rhinella arenarum (Anura: Bufonidae)

“…The pulse exposure conditions provided the opportunity to record that most of the sublethal effects observed were, at least partially, reversed within 168 h post-treatment. These results could be related to the notorious shape regulation capacity of vertebrate organisms during their early life stages (Herkovits and Faber 1978), and also point out the magnitude of damage caused by ATR in the case of persistent malformations. Although concentrations used in 24 h pulse-exposures may be considered very high and not environmentally relevant, the results might anticipate the effects of the herbicide on amphibian development, as a result of spill situations.…”

Evoecotoxicology: Environmental Changes and Life Features Development duringthe Evolutionary Process—the Record of the Past at DevelopmentalStages of Living Organisms

“…Some agents or combinations of agents with novel mechanisms for adverse effects probably represent exceptions to this generalization. However, the fact that early organogenic-stage embryos in general are very susceptible to noxious agents [in spite of high capacity to recover from adverse effects ( Herkovits 1977 ; Herkovits and Faber 1978 ; Herkovits and Fernandez 1979 )] contributes to the vision that the increasing complexity of cell differentiation and morphogenesis is associated with relatively low environmental stress conditions during evolution that are reflected in ontogeny. It is noteworthy that metamorphosis, also a complex cell differentiation and morphogenetic process in both invertebrates and vertebrates, is another period of very high susceptibility to a variety of environmental agents ( Howe et al 2004 ; Wilson 2004 ; Zhang 2002 ).…”