Evidence from polychromatism and bioluminescence that the cosmopolitan ophiuroid Amphipholis squamata might not represent a unique taxon

Individuals of the cosmopolitan ophiuroid Amphipholis squamata were collected from eight stations. Eleven colour varieties were described and their distribution was non-random among stations. This suggests that the varieties differ in ecophysiologic tolerance and that their geographical distribution is modulated by environmental conditions. Varieties also differed in bioluminescence. Contrary to kinetics, intensity of light production varied among co-occurring varieties, meaning that they have similar bioluminescent reactions but a different amount of bioluminescent reagent. Light intensity differed in absolute value among stations but the rank position of each variety relative to others remained constant from one station to another. The 'colour-bioluminescence' link appeared clearly fixed (the same level of bioluminescence for the same variety) and is suggested to be of genetic origin. The species 'A. squamata' may then be a mosaic of genetically different entities (the varieties) rather than a unique cosmopolitan taxonomic entity. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.