Quantifying the Over-retraction (Ore) phenotype in male tail tip morphogenesis.

Morphometrics, the quantitative analysis of biological structures, reduces subjectivity and increases reproducibility in characterizing morphological phenotypes. In males, the rounded adult tail tip emerges from a stage-specific retraction of epidermal cells regulated by the heterochronic pathway via LIN-41/TRIM71. Precocious tail tip morphogenesis in reduction-of-function conditions results in a blunted tail (Ore) phenotype, previously described qualitatively (Del Rio-Albrechtsen et al., 2006). We present a quantitative method to assess the Ore phenotype by measuring the tail tip position relative to the cloacal opening. This method can be used to study variation in Ore phenotypes and to validate loss-of-function reagents.