Converts the 3-keto steroids 4-cholesten-3-one and lathosterone into the carboxylic metabolites 3-keto-4-cholestenate (Delta(4)-dafachronic acid, Delta(4)-DA) and 3-keto-7,(5a)-cholestenate (Delta(7)-dafachronic acid, Delta(7)-DA) respectively, by catalyzing successive oxidations at C-26 (PubMed:16529801, PubMed:22505847). Dafachronic acids bind directly to the nuclear hormone receptor (NHR) DAF-12, suppressing dauer formation and inducing reproductive growth (PubMed:11782415, PubMed:12783794, PubMed:16529801, PubMed:22505847). In a non-cell autonomous manner, negatively regulates body wall muscle arm extensions to motor neurons probably by preventing daf-12 isoform b activation (PubMed:18436204). May be involved in thermotolerance (PubMed:24957743). 5alpha-cholest-7-en-3-one + 3 O2 + 3 reduced [NADPH--hemoprotein reductase] = (25S)-Delta7-dafachronate + 4 H(+) + 4 H2O + 3 oxidized [NADPH--hemoprotein reductase] cholest-4-en-3-one + 3 O2 + 3 reduced [NADPH--hemoprotein reductase] = (25S)-3-oxocholest-4-en-26-oate + 4 H(+) + 4 H2O + 3 oxidized [NADPH--hemoprotein reductase] Steroid hormone biosynthesis; dafachronic acid biosynthesis. Localizes to dendrite-like structure in XXXL/R cells. Expressed in the 2 embryonic head hypodermal cells XXXL/R. The daf-9 mutant is dauer-like in head shape, cuticle, and deirid ultrastructure, intermediate in amphid and inner labial neuron morphology, and nondauer or abnormal in the intestine (PubMed:3350212). Also, the daf-9 mutant exhibits abnormal reproductive development, molting defects and increased adult longevity (PubMed:11782415). Belongs to the cytochrome P450 family.