TABLE 1.

Notable similarities and differences between major zebrafish organs and human counterparts.

Major zebrafish organs	Notable similarities to humans	Notable differences from humans
Brain	• Major brain regions (i.e., telencephalon, thalamus, cerebellum) are present (Menke et al., 2011) • Dopaminergic, serotonergic, and cholinergic neuronal populations are present (Parker et al., 2013) • Similar myelin structure (Preston and Macklin, 2015)	• Prefrontal cortex and expanded telencephalon are absent (Parker et al., 2013) • Some differences in topography (Parker et al., 2013)
Eyes	• Similar retinal cell layer architecture (Angueyra and Kindt, 2018) • Rods and cones are present, cone-dominant vision (Morris and Fadool, 2005; Chhetri et al., 2014)	• Lateral eyes, spheroid lens (Chhetri et al., 2014) • Also has UV-sensitive cones, tetrachromatic rather than trichromatic vision (Chhetri et al., 2014)
Heart	• First and second heart field progenitor populations have been identified (Asnani and Peterson, 2014) • Similar action potential and electrocardiogram profiles (Verkerk and Remme, 2012; Vornanen and Hassinen, 2016) • Fundamental current systems are present (Vornanen and Hassinen, 2016)	• Two-chambered heart (Asnani and Peterson, 2014) • Different ion channel depolarization/repolarization profiles (Verkerk and Remme, 2012) • Regeneration following partial tissue loss (Poss et al., 2002) • Diffusion-based oxygenation during early development (Asnani and Peterson, 2014)
Kidney	• Glomeruli, proximal/distal tubules, collecting ducts, and brush border membrane are present (Menke et al., 2011; Outtandy et al., 2019) • Major solute transporters and receptors are present (Outtandy et al., 2019)	• Pronephros rather than metanephros (Outtandy et al., 2019)
Liver	• All major mammalian liver cell types are present except Kupffer cells, cell type-specific functions are largely conserved (Goessling and Sadler, 2015; Pham et al., 2017) • Bile secretion via bile canaliculi (Goessling and Sadler, 2015; Pham et al., 2017)	• Kupffer cells are not observed (Goessling and Sadler, 2015; Pham et al., 2017) • Different cellular architecture (i.e., hepatocytes arranged into tubules, lobules and portal triads not present; Goessling and Sadler, 2015; Pham et al., 2017)
Pancreas	• Endocrine and exocrine compartments (Seth et al., 2013) • Acinar cells are present; β-, α-, δ-, and ε-cells produce insulin, glucagon, somatostatin, and ghrelin, respectively (Kinkel and Prince, 2009; Seth et al., 2013) • Similar islet architecture (Kinkel and Prince, 2009)	• Less discrete demarcation of organ (Menke et al., 2011)
Adipose tissue	• Multiple white adipose tissue depots, neutral lipid droplets are observable (Zang et al., 2018) • Adipose lineage expresses pparg and fabp4 (Flynn et al., 2009; Zang et al., 2018) • Major metabolic pathways (i.e., SREBFs, PPARs, LEP) are present (Oka et al., 2010; Zang et al., 2018)	• No brown adipose tissue (Zang et al., 2018)
Swim bladder	• Epithelial surfactants are found in swim bladder (Robertson et al., 2014) • Transcriptome shares similarities with mammalian lungs (Zheng et al., 2011; Cass et al., 2013)	• No lungs