Cellular dynamics involved in the narrowing of the first tarsal segment of the first leg of Drosophila melanogaster females used as a control for male sex comb rearrangements

Abstract

Development of most epithelial tissues involves complex rearrangements as seen in the sex comb rotation of male Drosophila melanogaster. The sex comb is a compact row of bristles found on the first tarsal segment of the first leg in male D. melanogaster, which undergoes a horizontal to vertical rotation during development. Females do not have sex combs, but despite this sexual dimorphism, the first tarsal segment of the first leg undergoes similar changes during the elongation stage of leg development. This leads to the question of what mechanisms are involved in leg elongation versus the rotation of the sex comb in males, and if female legs can be used as a control to understand the cellular dynamics of male leg elongation. To better understand the development of female D. melanogaster’s first tarsal segments, labeled confocal images from both sexes were studied starting from 23 hours after pupariation (AP), after the onset of the larval to pupal transition. It was found that the first tarsal segment of female D. melanogaster has fewer cases of cell intercalation and has types of cell rearrangements not previously described in males. Careful analysis of these cell rearrangements suggests that female D. melanogaster use a different mechanism for the narrowing of the distal portion of the first tarsal segment as expected due to the absence of the sex comb. We hypothesize that a global rotation of cells in the distal posterior region of the female first tarsal segment has a major role in the elongation process of the leg.