Relationship of dorsoventral eyeshine distributions to habitat depth and animal size in mesopelagic decapods.

Eyeshine distribution patterns recorded from the eyes of 19 mesopelagic decapod species were examined and related to the depths at which the species are found. For most species examined, eyeshine was found to be brighter ventrally than dorsally. Deep-water decapod species that do not undergo diel vertical migrations had brighter dorsal eyeshine than migratory species. Eyeshine intensity increased with body size in five of the species examined and decreased in two. These changes in eyeshine intensity may be an adaptation to variations in depth distributions that occur with increasing body size. It is suggested that the depth and size-related changes reflect the importance of remaining camouflaged in the mesopelagic realm and are an example of ecologically functional development.