Developmental mechanism of the tarsus in insect legs.

Insects show a tremendous morphological variety and have been a subject of studying morphological evolution. In legs, the tarsus is especially variable in the number of subsegments (tarsal segments) and their proportion unlike other leg segments. Recent studies in Drosophila melanogaster have revealed details of the tarsal development: regionalization of the tarsal region through integration of regulatory network and its growth, determination of the joint-forming region in each segment through strict regulation of Notch activity, changes in tissue morphology through regulation of RhoGTPases regulators and localized cell death, and finally, the morphogenetic mechanism of the ball-and-socket joint between tarsal segments. The substantial knowledge of the tarsal development makes it a suitable model for studying mechanisms of morphological evolution and diversification.