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Fig. 4 Decreased survival, abnormal gross morphology, and reduced swimming activity in dldh–/– zebrafish larvae. (A) dldh–/– larvae had reduced survival relative to WT larvae, with mortality starting at 8 dpf; n = 300 each strain, across 3 biological replicates; log-rank (Mantel-Cox) test: P < 0.0001; median survival of dldh–/–: 10 dpf. Death was defined by absent heartbeat. (B) Morphological analysis at 7 dpf showed dldh–/– zebrafish larvae had enlarged liver (white arrowhead), darker intestine (black arrows) with universal finding of uninflated swim bladder (asterisk in WT), relative to WT larvae. Scale bar: 0.5 mm. (C) Larval swimming activity (ZebraBox platform and ZebraLab software) tracing showed reduced dldh–/– mutant swimming (open circles) in dark periods (gray) at 7 dpf. Larvae were exposed to 3 consecutive 10-minute 100% light (yellow) and 10-minute dark cycles following a light/dark acclimation period. Each point shows average (mean + SEM) activity of 84 larvae/strain. (D) dldh–/– swimming activity at 7 dpf during dark cycles analyzed by AUC, with group comparison. ****P < 0.0001 by unpaired Student’s t test. Data are shown as mean ± SEM. n = 84 larvae across > 3 biological replicate experiments per strain.