OBSERVATIONS ON SKIN COLOR CHANGES IN JUVENILE LUMPSUCKERS

This study reports on an experimental investigation of colour change i n young lumpsuckers Cyclopterus lumpus, employing Munsell colour chart s to quantify skin hue, colour value and chroma. Juvenile lumpsuckers can live pelagically close to the sea surface, or can attach to floati ng seaweed and debris with their suckers. When swimming they adopt a c ryptic default light green coloration, with the dorsum being darker th an the belly (countershading). This default colour is also seen in com plete darkness. When attached to objects they rake a colour stimulus f rom below and to the sides and change colour. They can achieve good co lour matches (noticeable in 3 min; complete within 15 min) with substr ata that are green-yellow in colour, especially the brown alga Ascophy llum nodosum. Colour matching is largely dependent upon changes in col our value (i.e. lightness/darkness) produced by melanin dispersal or c oncentration in the melanophores. Thus, on artificial backgrounds outs ide the range of achievable hue matching, they still achieve good matc hings of colour value. Slight hue changes were recorded (probably refl ecting interaction of basic skin colour with melanin dispersal state), but chroma (brightness) variations were negligible. Lumpsucker colour depends upon light intensity, allowing sustained colour matching as w eed illumination changes. (C) 1995 The Fisheries Society of the Britis h Isles