Predator-induced phenotypic plasticity during early biological evolution and ROS suppression in the brain of Xenopus tropicalis

Abstract

Predator-induced adaptive phenotypic plasticity is essential for evolution. However, Xenopus tropicalis tadpoles do not exhibit distinct phenotypes when exposed to new predation threats. Here, we investigated adaptions within their brain. Principal component analysis using morphological parameters indicated that short-term predation threats (24 hr) altered tadpole morphology unlike the control or 5 day-out treatment (exposure to predation for 5 days and then no exposure for 5 days). Whole-brain ingenuity pathway and metabolome analyses revealed that free radicals, superoxide dismutase, glycogenesis, and pyruvate were elevated after 6 hr of predation pressure. Hemoglobin was also synthesized in the brain, forming oxyhemoglobin in the midbrain and hindbrain to reduce radical production. Furthermore, ATP production through glycolysis was promoted, while β-oxidation and the tricarboxylic acid cycle were downregulated. We also predicted increases in microtubule dynamics, neuronal branching, and neuritogenesis. Therefore, X. tropicalis tadpoles can adapt to predation stress through changes within their central nervous system.