The skin pattern of young plaice and its rapid modification in response to graded changes in background tint and pattern

Abstract

Young plaice, kept on a standard background and trained for 3–4 weeks, were photographed to record short‐term nervously controlled responses to plain grey and patterned backgrounds, graded and quantitatively defined with regard to reflectivity and dimensions. Systems of primary, secondary and lower‐order black and white spots and flecks became prominent or hidden in hierarchical order. Spots at any one level in a hierarchy were approximately evenly distributed. Black spots enlarged with increased size or number of black circles in the background but responded differently to unpatterned grey backgrounds. White spots had a centre and surrounding annulus both of which could be pale or independently variably occluded centrally, peripherally or overall. Peripheral occlusion of the annuli contributed to skin darkening and by extending inwards to include the centre it progressively diminished the white spots. The system of white spots was responsible for the smaller skin patterns, the finest being produced through disruption by the white flecks of the annuli, black spots and dark patches. There was great variation in response of individuals. Erratic and poor background responses were generally associated with abnormalities in the white spots.