More than meets the eye : Predator-induced pupil size plasticity in a teleost fish

• 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. 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. 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. 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. 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.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

Nyckelord

crucian carp

eye evolution

inducible defence

phenotypic plasticity

predator–prey interactions

pupil size

vision

visual ecology

avoidance reaction

foraging behavior

freshwater environment

nocturnal activity

predation risk

predator

teleost

Animalia

Carassius

Teleostei

article

controlled study

ecology

exercise

eye development

foraging

freshwater fish

human

light

nonhuman

predator prey interaction

pupil diameter

Biology

Biologi

crucian carp

eye evolution

inducible defence

phenotypic plasticity

predator–prey interactions

pupil size

vision

visual ecology

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)