Δ7-Dafachronic acid regulates the developmental switch controlling the homogonic or heterogonic fates of post-parasitic female larvae of Strongyloides stercoralis.

The frequency distribution of homogonically (red bar) and heterogonically (green bars) developing S. stercoralis post-parasitic females in cultures maintained at 22°C or at 37°C in the presence or absence of 1 μM Δ7-dafachronic acid (Δ7-DA) was plotted. Data are based on counts of worms, explanted to culture as hatchling first-stage larvae from the intestines of experimentally infected gerbils, scored for development at 24 and 48 hours of culture and assigned to one of two developmental classes representing larvae developing by the homogonic route to infectious third-stage larvae (iL3) or larvae developing via the heterogonic route to free-living females via rhabditiform second, third, and fourth larval stages (L4-FL Adult). Post-parasitic males were excluded from the analysis, as males only develop heterogonically. The bar height represents the mean of five biological replicates and the error bar +1 standard deviation. Brackets indicate statistical comparisons of iL3 frequency at 37°C to frequencies at both 22°C and 37°C with 1 μM Δ7-DA; *** indicates P < 0.001.