<i>daf-2</i> requires fission, not fusion, for reproductive longevity.

(A) Representative images of Day 4 adult mitochondrial morphology in the -1 oocyte marked with anti-ATP5α. White-dotted boxes are enlarged (right) of the morphology in the -1 oocyte (I and II). Scale bar 10μm. Images in A were processed using the same parameters across the entire image (i.e. adjusting for brightness and contrast). (B) Blind scoring results of mitochondrial morphology of the -1 oocyte in three categories: punctate, mixed, or elongated of daf-2(e1370) (n = 30), daf-2(e1370);drp-1(tm1108) (n = 46), and daf-2(e1370);fzo-1(tm1133) (n = 56). (C) Mitochondrial length measurements. Each dot is 1/3 measurements from the -1 oocyte from 20–25 individual hermaphrodites in each genotype. (D) Fission knockout daf-2(e1370);drp-1(tm1108) (n = 96) has a reduced reproductive span compared to daf-2(e1370) (n = 121) in mated hermaphrodites. (E) Fusion knockout daf-2(e1370);fzo-1(tm1133) (n = 101) maintain an elongated reproductive span compared to daf-2(e1370) (n = 102). In D and E † indicates loss of hermaphrodites due to high rates of matricide. (F) Late-mating of daf-2(e1370) (n = 103), daf-2(e1370);drp-1(tm1108) (n = 79), and daf-2(e1370);fzo-1(tm1133) (n = 102). Error bars represent 95% confidence interval. (G) Representative images of oocyte quality in daf-2(e1370) (left panel) and daf-2;drp-1 (right panel) in Day 8 adults. Highlighted features include: embryos in the uterus (white arrows), the -1 oocyte (black asterisk), uterine mass (yellow dotted outline). Scale bar is 20μm. (H) Quantification of oocyte quality phenotypes from daf-2(e1370) (n = 41) and daf-2(e1370);drp-1(tm1108) (n = 39) in Day 8 adults. (I) Oocyte quality does not decline with age in daf-2;fzo-1. Quantification of oocyte quality features in daf-2 (19–21) and daf-2;fzo-1 (30–33). (J) Embryonic lethality in daf-2(e1370);drp-1(tm1108) and daf-2(e1370). Representative data from days 3, 4, and 5 of adulthood are shown due to high rates of matricide after day 5 (n = 11–13). (K) Lifespans of daf-2(e1370);drp-1(tm1108) (n = 81) and daf-2(e1370) (n = 80) or (L) daf-2(e1370);fzo-1(tm1133) (n = 80) and daf-2(e1370) (n = 81) are unchanged. **p ≤ 0.01, ****p ≤ 0.0001.