Photoperiod and feeding behavior of the Antarctic fish Notothenia rossii (Perciformes: Nototheniidae) and functional morphology of chemical and visual sensory structures used in foraging

the influence of photoperiod on the ability of notothenia rossii richardson, 1844 to detect prey was studied experimentally. in 12l/12d there was the highest number of individuals stimulated visually and chemically while in 24d chemical perception was the same as that observed in 12l/12d, the latter being lower than in 24l. the ultrastructure of chemo- and photo-sensory structures, involved in the detection of food, was studied. the photoreceptor cells of the retina are single and double cones, and rods. taste buds were concentrated in the central part of upper and lower lips. their shape is even, but the size is variable. the olfactory rosette has a sensory and a non-sensory epithelium, being rich in different mucosubstances. the conclusion was that in different photoperiods there is a difference in the response to visual and chemical stimulation for prey detection and that all sensory systems are more stimulated in periods of more luminosity, mainly when there is an alternation between light and dark periods. sensory organs are complex when compared to some other antarctic fish such as gobionotothen gibberifrons l？nnberg, 1905 and ophthalmolycus amberensis tomo, marshoff & torno, 1977 but similar to those of n. coriiceps rchardson, 1844.