Physics

Somitogenesis

Heterochrony

Ontogeny

Evolutionary biology

Biology

Gene

Optics

Wavefront

Paleontology

Artificial intelligence

Arthropod

Vertebrate

Somite

Computer science

Computational biology

Embryogenesis

Genetics

Segmentation

Development

ABSTRACT There is now compelling evidence that many arthropods pattern their segments using a clock-and-wavefront mechanism, analogous to that operating during vertebrate somitogenesis. In this Review, we discuss how the arthropod segmentation clock generates a repeating sequence of pair-rule gene expression, and how this is converted into a segment-polarity pattern by ‘timing factor’ wavefronts associated with axial extension. We argue that the gene regulatory network that patterns segments may be relatively conserved, although the timing of segmentation varies widely, and double-segment periodicity appears to have evolved at least twice. Finally, we describe how the repeated evolution of a simultaneous (Drosophila-like) mode of segmentation within holometabolan insects can be explained by heterochronic shifts in timing factor expression plus extensive pre-patterning of the pair-rule genes.

Arthropod segmentation