Simplified schematic of regulatory neurological pathways of aggression in mammals targeted for this study in fish. Study genes are highlighted in red. Abbreviations: 5-HIAA, 5-hydroindoleacetic acid; 5-HT, 5-hydroxytryptamine (serotonin); 5-HTP, 5-hydroxytryptophan; AANAT, arylalkylamine N-acetyltransferase; ACTH, adrenocorticotropic hormone; ALD-DH, acetaldehyde dehydrogenase; AR, androgen receptor; AVT, arginine vasotocin; COMT, catechol-O-methyl transferase; CRH, corticotrophin releasing hormone; DAO, diamine oxidase; DAT, dopamine transporter; DOPA, dihydroxyphenylalanine; ER, estrogen receptor; FSH, follicle-stimulating hormone; GH, growth hormone; GHRH, growth hormone releasing hormone; GnRH, gonadotropin releasing hormone; GR, glucocorticoid receptor; HIOMT, hydroxyindole-O-methyltransferase; HMT, histamine-N-methyltransferase; HNS, hypothalamo-neurohypophysial system; HPI, hypothalamo-pituitary-interrrenal; HPG, hypothalamo-pituitary-gonadal; IL1β, interleukin 1β; LH, luteinizing hormone; MAO, monoamine oxidase; MR, mineralocorticoid receptor; NOS, nitric oxide synthase; NPY, neuropeptide Y; SERT, 5-HT transporter; TSH, thyrotropin-stimulating hormone. Plus (+) and negative (-) symbols indicate the proposed action of a gene/neurotransmitter/pathway on aggression (i.e. stimulatory or inhibitory, respectively).