Detection of fruit by theCerrado's marmoset (Callithrix penicillata): modeling color signals for different background scenarios and ambient light intensities

Abstract

Among placental mammals, only primates have trichromatic color vision, however this is not a uniform condition. Under different genetic status, Old World monkeys have routine trichromacy, while New World monkeys show a visual polymorphism, characterized by obligatory male dichromacy. The ecological role of this genetic difference still remains unclear, but some studies show that dichromats and trichromats appear to have different abilities in detecting colored targets against a background of leaves. The Cerrado's marmoset (Callithrix penicillata) is known to forage in brightly illuminated (savanna-like vegetation) and dimly illuminated (forests) environments, exploiting a high amount of dark fruits. Hence, it seems to be a good model for studying the differential advantages enjoyed by each color vision phenotype under natural conditions. Our aim was to verify how the different phenotypes of Cerrado's marmoset detect components of their diet, evaluating the existence of differential phenotype advantages. Under two different light conditions, visual signals of naturally consumed fruits were modeled against different backgrounds scenarios. Even though dichromats and trichromats appear to be equally suited for tasks involving fruit detection, phenotype differential advantages are observed in this marmoset. In many conditions trichromats are predicted to perform better than dichromats, but under low ambient light dichromats manage to outperform trichromats in some scenarios. Phenotypes that carry widely spaced and longer M/L pigments enjoy the most advantage. These differential performances of trichromatic phenotypes, together with overdominance selection, seem to explain the maintenance of the tri-allelic system found in callitrichids.

Color Vision Variation as Evidenced by Hybrid L/M Opsin Genes in Wild Populations of Trichromatic Alouatta New World Monkeys

“…It is still an open question whether the selection is for 1) simply maintaining heterozygotes of L/M opsin alleles, i.e., trichromacy per se ; 2) dichromacy and trichromacy; or 3) subtypic variation in dichromacy and/or trichromacy. It is known that normal trichromacy impedes some achromatic visual tasks such as breaking camouflage and motion detection, especially under low-light conditions (Kelber et al 2003; Morgan et al 1992; Perini et al 2009). Further studies of howlers’ visual behaviors and the genetics of the L/M opsin variation will be beneficial in determining whether mildly anomalous trichromacy is more advantageous than normal trichromacy in achromatic tasks while maintaining the advantage in chromatic tasks, relative to dichromacy.…”

Assessing Sexual Dicromatism: The Importance of Proper Parameterization in Tetrachromatic Visual Models

“…Studies comparing dicromats to trichromats [37, 38] and trichromats to tetrachromats [39, 40] have quantified how these visual systems differ in their ability to tell apart patches with different spectral properties. Others have tested the effect of different light environments [22, 41–43], photoreceptors sensitivities [22, 44], photoreceptor densities [44, 45], oil droplet characteristics [44, 46–48], ocular media [22], and receptor signal-to-noise ratio [44].…”

The adaptive value of primate color vision for predator detection

“…On the other hand, trichromatism has been suggested to be advantageous in the detection of conspicuous food [Mollon, ] (e.g., fruits [Sumner & Mollon, ] and “young” leaves [Dominy & Lucas, ]) against a green foliage background, and socio‐sexual signaling [Changizi et al, ]. However, a trichromatic advantage has not yet been clearly confirmed by field observations [Dominy et al, ; Melin et al, ; Smith et al, ], despite the predictions from modeling studies [De Araujo et al, ; Dominy & Lucas, ; Osorio & Vorobyev, ; Perini et al, ; Sumner & Mollon, ] and behavioral evidence [Caine & Mundy, ; Melin et al, ; Smith et al, ]. In fact, a few studies combining visual modeling and behavioral data suggest that color may not in fact play an essential role in short distance fruit detection [Hiramatsu et al, , ] or mate choice [Higham et al, ].…”