DIEL CYCLES IN HOPLOSTERNUM-LITTORALE (TELEOSTEI) - ENTRAINMENT OF FEEDING-ACTIVITY BY LOW INTENSITY COLORED LIGHT

Low intensity colored light is very often used to observe or manipulate fish during the scotophase. According to data on fish vision, most species can perceive these wavelengths of light since their cone pigments have maximum absorption peaks around 455, 530 and 625 nm. To test whether Hoplosternum littorale can detect low intensity red or blue light, we attempted to entrain feeding activity, known to be nocturnal and synchronized by the circadian light/dark alternation, to such light. Feeding activity was entrained with either red or blue light, indicating that these fish can perceive these lights. In all cases, the fish fed during the darker phase of the light cycle.