Abstract
- Teleost
fishes occupy a range of ecosystem and habitat types subject to large
seasonal fluctuations. Temperate fishes in particular, survive large
shifts in temperature, light availability, and access to certain
habitats across seasons. Yet, there is limited understanding of how
behavioral responses to a seasonally shifting environment might shape,
or be shaped by, the nervous system.
- Here we quantified variation in relative brain size and the size of
five externally visible brain regions in a freshwater top predator,
lake trout (Salvelinus namaycush ), across six consecutive
seasons in two different lakes. Acoustic telemetry data from one of
our study lakes was collected during the study period from a different
subset of individuals and used to infer relationships between brain
size and seasonal behaviors (habitat use and movement rate).
- Our results indicated that lake trout relative brain size was larger
in the fall and winter compared to the spring and summer in both
lakes. Larger brains coincided with increased use of nearshore lake
habitats and increased horizontal movement rates by lake trout in the
fall and winter based on acoustic telemetry. The telencephalon
followed the same pattern as whole brain size, while the other brain
regions (cerebellum, optic tectum, olfactory bulbs, hypothalamus) were
only smaller in the spring.
- Seasonal shifts in total brain size might reflect greater underlying
changes in the size of the telencephalon. These findings provide
evidence that flexibility in brain size could underpin shifts in
behavior which could subserve functions associated with differential
habitat use during cold and warm seasons and allow fish to succeed in
seasonally variable temperate environments.