The dynamics of mitochondria is disrupted in aass-1 SDH mutants. (A) Dynamics of Mito-GFP–labeled mitochondria in the hypodermis of an N2 L4 animal. White arrows indicate sites of mitochondrial fusion. Yellow arrows indicate sites of mitochondrial fission. (B) Dynamics of Mito-GFP–labeled mitochondria in hypodermal cells in an aass-1(yq170) L4 animal and an aass-1(yq170) adult animal. White arrows indicate sites of mitochondrial fusion. Purple arrows indicate mitochondria undergoing retraction. Asterisks label mitochondria undergoing fusion in aass-1(yq170) animals. Bars, 5 µm. (C) Quantification of the frequency of fusion and fission events in N2 and aass-1(yq170) mutants. (D) Representative images of mitochondria in the hypodermis of N2, aass-1(yq170) single mutants, fzo-1(tm1133) single mutants, fzo-1(tm1133);aass-1(yq170) double mutants, and eat-3 RNAi-treated N2 and aass-1(yq170) animals. Bars, 5 µm. (E) Images of the rescuing effects on drp-1(tm1108) mitochondria of GFP::DRP-1. Bars, 5 µm. Boxed regions of mitochondria are magnified (3×) and shown in the bottom left corners of the corresponding images. (F and G) Representative images of TOMM-20::mCherry-labeled mitochondria and GFP::DRP-1 in the hypodermis of N2 (F) and aass-1(yq170) (G) animals. Boxed regions are magnified (3×) and shown on the right of each image. Bars, 3 µm. (H) Percentage of GFP::DRP-1 at mitochondrial constriction sites in N2 and aass-1(yq170) animals. Five animals were analyzed for each genotype. (I) Diameters of mitochondria positive for GFP::DRP-1 in N2 and aass-1(yq170) animals. Five animals were analyzed for each genotype. (J) Representative images of TOMM-20::mCh-labeled mitochondria and GFP::TRAM-labeled ER in the hypodermis of N2 and aass-1(yq170) animals. Boxed regions are magnified (3×) and shown on the right of each image. Arrows indicate the sites where mitochondria are crossed by ER tubules. Bars, 5 µm. For all quantifications, *, P < 0.05; **, P < 0.01; and ***, P < 0.001. Error bars represent SEM.