Eric Warrant

..The ability of many animals to camouflage themselves against a background is a well-known daytime phenomenon. Now it has even been found to occur at night, highlighting the reality of nocturnal visual predation...

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..The same is certainly true of deep-sea animals, as future research will no doubt reveal...

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..But in brighter light, rods become energetically 'cheaper' than cones, which might explain the evolution of the vertebrate duplex retina...

..The insensitive optics of apposition eyes are not well suited for nocturnal vision. How well then do nocturnal bees and wasps see? What optical and neural adaptations have they evolved for nocturnal vision?..

..It has long been known that the iridescent cuticle of many scarab beetles reflects circularly polarised light. It now turns out that scarabs can also see this light, potentially using it as a covert visual signal...

..These four classes of orientation--and their visual basis--are reviewed here, with special emphasis given to the best-understood animal systems that are representative of each...

..We propose that neural pooling strategies and behavioural adaptations precede anatomical adaptations in the eyes and ocelli when insects with apposition compound eyes turn to dim light activity...

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..To our knowledge, this is the only animal with a visual compass system that ignores the extra orientation precision that landmarks can offer...

..Exactly where in the visual system this summation takes place, and the nature of the neural circuitry that is involved, is currently unknown but provides a promising avenue for future research...

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..tranquebarica in extremely dim light. We hypothesise that additional adaptations must confer extreme nocturnality in X. tranquebarica...

..Intracellular recordings within the dorsal rim area show very high polarisation sensitivity and a sensitivity peak within the ultraviolet part of the spectrum...

..memnon than in M. peleides, showing that adaptations that improve sensitivity can be found not only in nocturnal apposition eyes, but also on a smaller scale in crepuscular apposition eyes...

..It is concluded that dragonfly ocelli employ a number of simple, yet elegant, anatomical and optical strategies to ensure high sensitivity, fast transduction speed, wide fields of views and a modicum of spatial resolving power...

..Taken together, our results show that colour vision occurs at nocturnal intensities in a biologically relevant context...

..This extreme reaction-which is routine in Moken children-is completely absent in European children. Because they are completely dependent on the sea, the Moken are very likely to derive great benefit from this strategy...

..New evidence suggests that additional neuronal spatial summation within the first optic ganglion, the lamina, is involved...

..7 and 12.9, similar to values recorded in diurnal navigators. These results agree with earlier results suggesting that the detection and analysis of polarized skylight is similar in diurnal and nocturnal insects...

..genalis indicates a potential role for these neurons in the spatial summation of photons from large groups of ommatidia. This specific adaptation in the nocturnal bee could significantly improve reliability of vision in dim light...

..The enhanced temporal resolution allowed by heated eyes provides warm-blooded and highly visual oceanic predators, such as swordfishes, tunas, and sharks, with a crucial advantage over their agile, cold-blooded prey...

..Theoretical and future physiological work should further elucidate the roles that this lateral spreading plays to improve dim-light vision in nocturnal insects...

..Improved reliability costs acuity, but dark adapted bees already suffer optical blurring, and summation further degrades vision only slightly...

..The achieved performance can be explained by the combined effect of pupil constriction and strong accommodation...

..Additionally, local neural properties vary across the visual world in a way not expected if HS cells serve purely as matched filters to measure yaw-induced visual motion...

..Contrary to the classical view it is concluded that some capacity for resolution is present in the locust ocelli...

..This study also suggests that perched males direct their most acute vision where females are likely to appear but show no eye modifications that appear clearly related to a mate-locating tactic...

..The results are discussed in relation to the evolution of lepidopteran eyes, and the sensory ecology of this poorly understood butterfly superfamily...

..These data agree well with the premise that Megalopta uses visual summation, sacrificing acuity in order to see and fly at the very dimmest light intensities that its visual system allows...