Data from: More than meets the eye: predator-induced pupil size plasticity in a teleost fish

1. Most animals are visually oriented, and their eyes provide their
“window to the world”. Eye size correlates positively with visual
performance, because larger eyes can house larger pupils that increase
photon catch and contrast discrimination, particularly under dim light,
which have positive effects on behaviours that enhance fitness, including
predator avoidance and foraging. 2. Recent studies have linked predation
risk to selection for larger eyes and pupils, and such changes should be
of importance for the majority of teleost fishes as they have a pupil that
is fixed in size (eyes lack a pupillary sphincter muscle) and, hence, do
not respond to changes in light conditions. 3. Here, we quantify eye and
pupil size of individual crucian carp, a common freshwater fish, following
controlled manipulations of perceived predation risk (presence/absence).
We also tested if crucian carp responded to increased predation risk by
shifts in diel activity patterns. 4. We found that crucian carp show
phenotypic plasticity with regards to pupil size, but not eye size, as
pupil size increased when exposed to predators (pike). Predator-exposed
crucian carp also shifted from diurnal to nocturnal activity. Using a
modelling exercise, we moreover show that the plastically enlarged pupils
significantly increase visual range, especially for small objects under
dim light conditions. 5. Overall, our results provide compelling evidence
for predator-induced pupil enlargement resulting in enhanced visual
capabilities in a teleost fish. Pupil-size plasticity in combination with
the observed shift towards nocturnal activity may allow for efficient
foraging also under dark conditions when predation risk from diurnal and
visually oriented predators is reduced. The data highlight the powerful
role of predation risk for eye development and evolution. 03-Jul-2020