Visual acuity of the summer flounder (Paralichthys dentatus) captures spatial information relevant to dynamic camouflage at close range.

Dynamic camouflage is the capacity to rapidly change skin color and pattern, often for the purpose of background-matching camouflage. Summer flounder (Paralichthys dentatus) are demersal fish with an exceptional capacity for dynamic camouflage, but with eyes that face away from the substrate, it is unknown if this behavior is mediated by vision. Past studies have shown that summer flounder skin can match the pattern (i.e., spatial detail) of substrate with a high degree of precision, and for that to be achieved using sight, one testable assumption is that the resolution of vision must match the degree of detail produced in color-change performance. To test this, approaches in morphology and behavior were used to estimate visual acuity, which is the capacity of the visual system to resolve static spatial detail. Using image processing techniques, we then compared the degree of spatial detail from a relevant substrate with what may be detectable by summer flounder spatial vision. The morphological and behavioral estimates of visual acuity were calculated as 3.62 cycles per degree (CPD) ± 0.8 (s.d.) and 4.06 CPD ± 0.4 (s.d.), respectively. These estimates fall within a range of acuities known among other flatfishes and appear adequate for detecting the spatial information needed for background-matching camouflage, though only at close distances. These data provide new knowledge about summer flounder visual acuity and suggest the capacity of flounder vision to support dynamic camouflage of the skin.