Low-Dose Psilocybin Cuts Escalated Aggression in Mangrove Rivulus Fish

The team used three genetically identical lines of self-fertilizing Kryptolebias marmoratus to control for heredity. Baseline aggression was recorded when fish could see but not touch each other across a mesh barrier; the next day the same individuals received dissolved psilocybin before a second encounter. Activity and high-energy attack bursts declined markedly while normal social signaling persisted.

These results extend known serotonin-receptor effects of psilocybin from mammals to a highly aggressive teleost, showing selective dampening of escalation without broad sedation. Because the fish are naturally solitary and highly territorial, the model isolates escalated aggression more cleanly than rodent resident-intruder tests.

Key limitation is the single acute dose and short observation window; chronic exposure, dose-response curves, and receptor-blocking controls are absent. Larger sample sizes across additional genetic lines plus parallel neurochemical assays would strengthen causal claims before any translational inference.