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Figure 5. Model schematic.(A) Diagrams of blastopore closure from the lateral side. The ectoderm and neurectoderm (gray) spreads over the embryo during gastrulation. Involution begins on the dorsal side at t = 0, and begins on the ventral side at tP; the blastopore closes at tC. In the generalized model (Model 1) we assumed all morphogenetic durations (tP, tC, etc) changed by the same proportion with temperature. In the step and ramp models (Models 2A & B) tP is used, as an estimate of the timing of cell behaviors that exert morphogenetic forces, to predict tC. A strip of tissue (A, to right of each whole embryo schematic) experiences spatially and temporally varying stresses (open arrows; stresses from deep tissues not shown), which elongate it and change its shape. We approximate this deformation as uniform stretching of a strip of material (B). The generalized model (Model 1) assumes temperature only affects the speed of morphogenesis, therefore each morphogenetic event occurs at fixed, but unspecified strains (εP,εC,…). In the step and ramp models (Models 2A & B) the main forces driving blastopore closure begin near the start of ventral involution (so ε[0]≈0), and blastopore closure occurs at a fixed strain (ε[tC] = εC); however, the strain at tP varies with temperature. Image published in: von Dassow M et al. (2014) Image reproduced on Xenbase with permission of the publisher and the copyright holder. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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