Rapid neural DNA methylation responses to predation stress in Trinidadian guppies

DNA methylation (DNAm) is a well-studied epigenetic mechanism implicated
in environmentally induced phenotypes and phenotypic plasticity. However,
few studies investigate the time scale of DNAm shifts. Thus, it is
uncertain whether DNAm can change on timescales relevant for rapid
phenotypic shifts, such as during the expression of short-term behavioural
plasticity. DNAm could be especially reactive in the brain, potentially
increasing its relevance for behavioural plasticity. Most research
investigating neural changes in methylation has been conducted in
mammalian systems, on isolated individuals, and using stressors that are
less ecologically relevant, reducing their generalizability to other
natural systems. We exposed pairs of male and female Trinidadian guppies
(Poecilia reticulata) to alarm cue, conspecific skin extract that reliably
induces anti-predator behaviour, or a control cue. Whole genome bisulfite
sequencing on whole brains at various time points following cue exposure
(0.5h, 1h, 4h, 24h, and 72h) allowed us to uncover the timescale of neural
DNAm responses. Males and females both showed rapid shifts in DNAm in as
little as 0.5 hours. However, males and females differed in the
time-course of their responses: both sexes showed a peak in the number of
loci showing significant responses at 4 hours but males showed an
additional peak at 72 hours. We suggest that this finding could be due to
differing longer-term plastic responses between the sexes. This study
shows that DNAm can be rapidly induced by an ecologically relevant
stressor in fish and suggests that DNA methylation could be involved in
short-term behavioural plasticity.