The colour vision of many primates is trichromatic, whereas that of all other mammals is thought to be dichromatic or monochromatic. Moreover, the triplets of cone pigments in different catarrhines (Old World apes and monkeys) are strikingly similar in their spectral positions. We ask whether the selective advantage of trichromacy lies in an enhanced ability to find edible leaves or fruit. Further, we ask whether any factor in these two search tasks has constrained the particular set of cone spectral sensitivities observed in all catarrhines. We measured the spectral properties of the natural environments of six primate species in Uganda: Pan troglodytes, Cercopithecus mitis, Cercopithecus ascanius, Lophocebus albigena, Colobus guereza and Colobus badius. We concentrated on the fruit and leaves in their diets and the leaves of the trees that make up the background against which these diet items must be found. We plotted these measured stimuli in colour spaces appropriate for each primate species, and found that both frugivory and folivory are facilitated by the extra dimension of colour vision found in catarrhines but lacking in most other mammals. Furthermore, by treating the task of searching for food as a signal-detection task, we show that, of all possible combinations of cone sensitivities, the spectral positions of the actual primate pigments are optimal for finding fruit or young leaves against the background of mature leaves. This is because the variance of the chromaticities of the mature leaves is minimised in one channel of the primate's colour vision, so allowing anything that is not a mature leaf to stand out.
Catarrhine photopigments are optimized for detecting targets against a foliage background
P. Sumner, J.D. Mollon; Catarrhine photopigments are optimized for detecting targets against a foliage background. J Exp Biol 1 July 2000; 203 (13): 1963–1986. doi: https://doi.org/10.1242/jeb.203.13.1963
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Meet the JEB Editors @ SEB 2023
Come and meet the JEB team at the Society for Experimental Biology centenary conference from 4-7 July in Edinburgh, UK. Visit exhibition stand 13/15 to pick up JEB centenary goodies, including our new ‘100 years of discovery’ T shirt, and join our Meet the JEB Editors event on Thursday 6 July at 12.30 at Platform 5 to find out more about the journal and chat to Editors including EiC Craig Franklin, Monitoring Editors Sanjay Sane, Trish Schulte and John Terblanche and the in-house News and Reviews team.
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Centenary Review - Adaptive echolocation behavior
Cynthia F. Moss and colleagues discuss the behaviours used by echolocating mammals to track and intercept moving prey, interrogate dynamic sonar scenes, and exploit visual and passive acoustic stimuli.
Crucial DNA at crux of insect wing size evolution
Keity Farfán-Pira and colleagues have revealed that a tiny region of regulatory DNA in the vestigial gene governs whether insect wings are large or small and has played a key role in the evolution of insect wing size.