Eyeshine in the scorpionfish <i>Scorpaena porcus</i> induced by a diffuse white reflective strip of paper in the field (video) from Controlled iris radiance in a diurnal fish looking at prey

Eyeshine can be induced by moving a strip of white paper in front of a scorpionfish (<i>Scorpaena porcus</i>), illustrating that even weak sources can induce a perceptible effect. An important property of <i>retro</i>-reflective eyeshine is that the effect is only visible when the source (the paper) is in line with the viewing angle of the camera. <b>Methods:</b> The scorpionfish is shaded, only illuminated by natural side-welling light and natural downwelling light diffusely reflected off a narrow strip of underwater paper (white at the side pointing at the scorpionfish, black at the back). The strip measures approx. 1.5 mm across at the position of the scorpionfish's eye and was held about 5 cm away. The effect weakens with distance, but can be seen by a human observer over a distance of up to 40 cm. Recording made at 15 m depth under natural field conditions in Calvi, Corsica using a Nikon AW130 compact camera with manual white balance, no filter or other light source. The sequence is shown forward and reversed, repeated 3 times (video by N.K.M.)