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PubMed1994

Evolution of the primate cytochrome c oxidase subunit II gene.

We examined the nucleotide and amino acid sequence variation of the cytochrome c oxidase subunit II (COII) gene from 25 primates (4 hominoids, 8 Old World monkeys, 2 New World monkeys, 2 tarsiers, 7 lemuriforms, 2 lorisiforms). Marginal support was found for three phylogenetic conclusions: (1) sister-group relationship between tarsiers and a monkey/ape clade, (2) placement of the aye-aye (Daubentonia) sister to all other strepsirhine primates, and (3) rejection of a sister-group relationship of dwarf lemurs (i.e., Cheirogaleus) with lorisiform primates. Stronger support was found for a sister-group relationship between the ring-tail lemur (Lemur catta) and the gentle lemurs (Hapalemur). In congruence with previous studies on COII, we found that the monkeys and apes have undergone a nearly two-fold increase in the rate of amino acid replacement relative to other primates. Although functionally important amino acids are generally conserved among all primates, the acceleration in amino acid replacements in higher primates is associated with increased variation in the amino terminal end of the protein. Additionally, the replacement of two carboxyl-bearing residues (glutamate and aspartate) at positions 114 and 115 may provide a partial explanation for the poor enzyme kinetics in cross-reactions between the cytochromes c and cytochrome c oxidases of higher primates and other mammals.

Amino Acid Sequence↗

PubMed1994

Coraco-clavicular joint: normal variant in humans. A radiographic demonstration in the human and non-human primate.

The coraco-clavicular joint is a true synovial joint that may become painful in some patients after trauma. Among the descriptions of this entity is the assertion that the coraco-clavicular joint is routinely seen in gorillas and gibbons. We undertook to assess the incidence of this variant among gorillas, gibbons, and other non-human primates. All available radiographs of large primates performed at the International Wildlife Conservation Park/Bronx Zoo (IWCP) over the past 10 years were reviewed by a musculoskeletal radiologist (human radiology). All radiographs were taken during the normal clinical care of the non-human primate population of the IWCP and are a part of each animal's clinical record. Eighty-one non-human primate radiographs were suitable for study as they contained the region of interest. The 81 radiographic examinations included 14 different species of non-human primates. The coraco-clavicular joint was seen in 4 out of 9 silver-leaf langur, 2 out of 8 lowland gorilla, and in 1 out of 6 white-handed gibbon. In all non-human primate cases where the coraco-clavicular joint occurred, it was bilateral. In 1 out of 8 mandrill, there were very wide distal clavicular ends that articulated both with the coracoid and with the acromion. The coraco-clavicular joint differs from an ossified coraco-clavicular ligament. The radiographic appearance is characteristic and is found in both humans and some non-human primate species. It may rarely become painful following trauma. When symptomatic in humans, resection of this anomalous articulation is curative.

Acromioclavicular Joint↗

PubMed1989

Effects of environmental conditions on the psychological well-being of primates: a review of the literature.

Amendments made to the Animal Welfare Act in 1985 require primate researchers to provide "a physical environment adequate to promote the psychological well-being of primates". Regulations have not yet been promulgated, in part because "the psychological well-being" of primates is extremely difficult to define. Ideally, those regulations would be based upon observable changes in behavior rather than assumed psychological changes. Regardless, new primate care regulations pertaining to social environment, cage size, exercise and other forms of environmental enrichment are anticipated. A review of the literature suggests that there is little scientific data to support changing existing regulations. For instance, although it is clear that total social isolation in very young primates can be behaviorally devastating in terms of normal social behaviors, there are few, if any, demonstrable adverse effects of individual housing in adult primates. On the other hand, group housing, particularly with groups changing frequently in composition, increases aggression, trauma and disease transmission. In addition, existing research suggests there are important species differences in terms of social preferences. It is impossible to justify an increase in cage size based upon the available literature. An additional practical consideration is that any change in cage size requirements will necessitate replacement of current primate housing on a national level, an enormously expensive proposition. Regarding environmental enrichment, research suggests that providing a naturalistic environment is not as critical as arranging dynamic events that are contingent upon behavior. However, new research is necessary to specify the types of environmental enrichment that are valuable and appropriate before useless, even damaging, and expensive changes are mandated.

Animal Welfare↗

PubMed2006

Effects of activity pattern on eye size and orbital aperture size in primates.

Among primates, nocturnal species exhibit relatively larger orbital apertures than diurnal species. Most researchers have considered this disparity in orbital aperture size to reflect differences in eye size, with nocturnal primates having relatively large eyes in order to maximize visual sensitivity. Presumed changes in eye size due to shifts in activity pattern are an integral part of theoretical explanations for many derived features of anthropoids, including highly convergent orbits and a postorbital septum. Here I show that despite clear differences in relative orbital aperture size, many diurnal and nocturnal primates do not differ in relative eye size. Among nocturnal primates, relative eye size is influenced by diet. Nocturnal visual predators (e.g., Tarsius, Loris, and Galago moholi) tend to have larger relative eye sizes than diurnal primates. By contrast, nocturnal frugivores (e.g., Perodicticus, Nycticebus, and Cheirogaleus) have relative eye sizes that are comparable to those of diurnal primates. Although some variation in orbital aperture size can be attributed to variation in eye size, both cornea size and orbit orientation also exert a strong influence on orbital aperture size. These findings argue for caution in the use of relative orbital aperture size as an indicator of activity pattern in fossil primates. These findings further suggest that existing scenarios for the evolution of unique orbital morphologies in anthropoids must be modified to reflect the importance of ecological variables other than activity pattern.

Animals↗

PubMed2003

Historical contingency in the evolution of primate color vision.

Primates are unique among eutherian mammals for possessing three types of retinal cone. Curiously, catarrhines, platyrrhines, and strepsirhines share this anatomy to different extents, and no hypothesis has hitherto accounted for this variability. Here we propose that the historical biogeography of figs and arborescent palms accounts for the global variation in primate color vision. Specifically, we suggest that primates invaded Paleogene forests characterized by figs and palms, the fruits of which played a keystone function. Primates not only relied on such resources, but also provided high-quality seed dispersal. In turn, figs and palms lost or simply did not evolve conspicuous coloration, as this conferred little advantage for attracting mammals. We suggest that the abundance and coloration of figs and palms offered a selective advantage to foraging groups with mixed capabilities for chromatic distinction. Climatic cooling at the end of the Eocene and into the Neogene resulted in widespread regional extinction or decimation of palms and (probably) figs. In regions where figs and palms became scarce, we suggest primates evolved routine trichromatic vision in order to exploit proteinaceous young leaves as a replacement resource. A survey of the hue and biogeography of extant figs and palms provides some empirical support. Where these resources are infrequent, primates are routinely trichromatic and consume young leaves during seasonal periods of fruit dearth. These results imply a link between the differential evolution of primate color vision and climatic changes during the Eocene-Oligocene transition.

Animals↗

PubMed2001

Visual cortex organization in primates: theories of V3 and adjoining visual areas.

After years of experimentation and substantial progress, there is still only limited agreement on how visual cortex in primates is organized, and what features of this organization are variable or stable across lines of primate phylogeny. Only three visual areas, V1, V2, and MT, are widely recognized as common to all primates, although there are certainly more. Here we consider various concepts of how the cortex along the outer border of V2 is organized. An early proposal was that this region is occupied by a V3 that is as wide and as long as V2, and represents the visual hemifield as a mirror image of V2. We refer to this notion as the classical V3 or V3-C. Another proposal is that only the dorsal half of V3-C exists, the half representing the lower visual quadrant, and thus the representation is incomplete (V3-I) by half. A version of this proposal is that V3-I is discontinuous, extremely thin in places, and highly variable across individuals, much as a vestigial or degenerate structure might be (V3-IF-incomplete and fragmented). A fourth proposal is that there is no V3. Many results suggest that a series of visual areas border V2, none of which has the characteristics of V3. Alternatively, the possibility exists that primate taxa differ with regard to visual areas bordering V2. Currently, much of the supporting evidence for a classical V3 comes from fMRI studies in humans, much of the evidence for a series of bordering areas comes from New World Monkeys and prosimian galagos, and much of the evidence for a V3-I or V3-IF comes from macaque monkeys. Possibly all these interpretations of visual cortex organization are valid, but each for only one of the major groups of primate evolution. Here, we suggest that none of these interpretations is correct, and propose instead that a modified V3 (V3-M) exists in a similar form in all primates. This V3-M is smaller and thinner than V3-C, discontinuous in the middle, but with comparable dorsal and ventral halves representing the lower and upper visual hemifields, respectively. Because the evidence for V3-M is limited, and it stems in part from our ongoing but incomplete comparative studies of V1 connections in primates, this suggestion requires further experimental evaluation and it remains tentative.

Animals↗

PubMed2001

Comparative expression of hedonic impact: affective reactions to taste by human infants and other primates.

This study examines behavioral affective reactions elicited by tastes from eight newborn human infants, and from 27 other infant or adult primates. Non-human primates belonged to 11 species: three great apes (chimpanzee, orangutan, gorilla), three Old World monkeys (rhesus monkey, greater spot-nosed monkey, and red-capped mangabey), four New World monkeys (golden-handed tamarin, cotton-top tamarin, white tufted-ear marmoset, and Humboldt's night monkey), and one lemur (mongoose lemur). The taste of sucrose elicited homologous positive hedonic patterns of facial affective reactions from humans and other primates, whereas quinine elicited homologous aversive or negative affective patterns. The degree of similarity between human and other primate affective reaction patterns appeared to be strongly indicative of their phylogenetic relatedness. For example, affective reaction patterns of human infants and great apes were more similar to each other than either were to Old World monkeys or New World monkeys. Certain affective reaction components were found to be shared by humans and all primates, whereas other components were restricted to particular taxonomic groups. Finally, allometric timing parameters for the duration of components indicated that the 'same' affective reaction could have different durations in species of different size. These results show that both positive/negative valence and intensity of affective reaction may be quantitatively assessed in human and non-human primates, and indicate that taste-elicited affective reaction patterns of human infants are related systematically to those of other primate species.

Affect↗

PubMed2003

Reproductive/developmental toxicity and immunotoxicity assessment in the nonhuman primate model.

Nonhuman primates are being used increasingly as a non-rodent animal model during preclinical toxicology and safety assessment on the basis of proven similarity and comparability between nonhuman primates and humans. The validity of the nonhuman primate models applies to many aspects of toxicological testing and holds particularly true for the evaluation of reproductive toxicology and developmental toxicology. More recently, the advent of humanized antibodies and vaccines imposed further demand on nonhuman primate models since many immunotherapeutics do not interact with rodent receptors but frequently only cross-react with primate tissue. In this paper we discuss the suitability of primate models for reproductive, developmental and immunotoxicology testing, and present our initial data on the development of lymphatic organs and immune system in a nonhuman primate model.

Abnormalities, Drug-Induced↗

PubMed2000

The connections of the dopaminergic system with the striatum in rats and primates: an analysis with respect to the functional and compartmental organization of the striatum.

This Commentary compares the connections of the dopaminergic system with the striatum in rats and primates with respect to two levels of striatal organization: a tripartite functional (motor, associative and limbic) subdivision and a compartmental (patch/striosome-matrix) subdivision. The topography of other basal ganglia projections to the dopaminergic system with respect to their tripartite functional subdivision is also reviewed. This examination indicates that, in rats and primates, the following observations can be made. (1) The limbic striatum reciprocates its dopaminergic input and in addition innervates most of the dopaminergic neurons projecting to the associative and motor striatum, whereas the motor and associative striatum reciprocate only part of their dopaminergic input. Therefore, the connections of the three striatal subregions with the dopaminergic system are asymmetrical, but the direction of asymmetry differs between the limbic versus the motor and associative striatum. (2) The limbic striatum provides the main striatal input to dopamine cell bodies and proximal dendrites, with some contribution from a subset of neurons in the associative and motor striatum (patch neurons in rats; an unspecified group of neurons in primates), while striatal input to the ventrally extending dopamine dendrites arises mainly from a subset of neurons in the associative and motor striatum (matrix neurons in rats; an unspecified group of neurons in primates). (3) Projections from functionally corresponding subdivisions of the striatum, pallidum and subthalamic nucleus to the dopaminergic system overlap, but the specific targets (dopamine cells, dopamine dendrites, GABA cells) of these projections differ. Major differences include the following. (1) In rats, neurons projecting to the motor and associative striatum reside in distinct regions, while in primates they are arranged in interdigitating clusters. (2) In rats, the terminal fields of projections arising from the motor and associative striatum are largely segregated, while in primates they are not. (3) In rats, patch- and matrix-projecting dopamine cells are organized in spatially, morphologically, histochemically and hodologically distinct ventral and dorsal tiers, while in primates there is no (bi)division of the dopaminergic system that results in two areas which have all the characteristics of the two tiers in rats. Based on the anatomical data and known dopamine cell physiology, we forward an hypothesis regarding the influence of the basal ganglia on dopamine cell activity which captures at least part of the complex interplay taking place within the substantia nigra between projections arising from the different basal ganglia nuclei. Finally, we incorporate the striatal connections with the dopaminergic system into an open-interconnected scheme of basal ganglia-thalamocortical circuitry.

Animals↗

PubMed2000

Nonhuman primate models in biogerontology.

A variety of animal models are utilized in biogerontological studies including yeast, nematodes, fruit flies, hamsters, mice, rats, and nonhuman primates. Species selection for research is based on many factors including economic feasibility, husbandry, generalizability of findings, available background information, adaptability to experimentation, and often, relevance to human aging. Each model offers its own strengths and limitations; however, nonhuman primates offer the unique advantage of phylogenetic proximity to humans. Among others, costs to purchase and maintain research subjects represent major limitations of nonhuman primate models. Although several nonhuman primate species have been utilized in aging research, rhesus monkeys (Macaca mulatta) are the best characterized and most extensively studied in biomedical gerontology. Nonhuman primate models have been employed as models for human aging in many research areas including neurobiology, skeletal, and reproductive aging and age-related diseases such as cardiovascular disease and diabetes. Primate models are now also being utilized to study interventions into aging such as caloric restriction. It will be several more years until definitive conclusions regarding lifespan effects can be made. However, existing data strongly suggest that many of the beneficial effects reported in rodents on CR also occur in primate models thereby strengthening the possibility that this nutritional paradigm may also impact favorably upon human aging.

Aging↗

PubMed2000

Origin and evolution of primate social organisation: a reconstruction.

The evolution and origin of primate social organisation has attracted the attention of many researchers, and a solitary pattern, believed to be present in most nocturnal prosimians, has been generally considered as the most primitive system. Nocturnal prosimians are in fact mostly seen alone during their nightly activities and therefore termed 'solitary foragers', but that does not mean that they are not social. Moreover, designating their social organisation as 'solitary', implies that their way of life is uniform in all species. It has, however, emerged over the last decades that all of them exhibit not only some kind of social network but also that those networks differ among species. There is a need to classify these social networks in the same manner as with group-living (gregarious) animals if we wish to link up the different forms of primate social organisation with ecological, morphological or phylogenetic variables. In this review, we establish a basic classification based on spatial relations and sociality in order to describe and cope properly with the social organisation patterns of the different species of nocturnal prosimians and other mammals that do not forage in cohesive groups. In attempting to trace the ancestral pattern of primate social organisation, the Malagasy mouse and dwarf lemurs and the Afro-Asian bushbabies and lorises are of special interest because they are thought to approach the ancestral conditions most closely. These species have generally been believed to exhibit a dispersed harem system as their pattern of social organisation ('dispersed' means that individuals forage solitarily but exhibit a social network). Therefore, the ancestral pattern of primate social organisation was inferred to be a dispersed harem. In fact, new field data on cheirogaleids combined with a review of patterns of social organisation in strepsirhines (lemurs, bushbabies and lorises) revealed that they exhibit either dispersed multi-male systems or dispersed monogamy rather than a dispersed harem system. Therefore, the concept of a dispersed harem system as the ancestral condition of primate social organisation can no longer be supported. In combination with data on social organisation patterns in 'primitive' placentals and marsupials, and in monotremes, it is in fact most probable that promiscuity is the ancestral pattern for mammalian social organisation. Subsequently, a dispersed multi-male system derived from promiscuity should be regarded as the ancestral condition for primates. We further suggest that the gregarious patterns of social organisation in Aotus and Avahi, and the dispersed form in Tarsius evolved from the gregarious patterns of diurnal primates rather than from the dispersed nocturnal type. It is consequently proposed that, in addition to Aotus and Tarsius, Avahi is also secondarily nocturnal.

Animals↗

PubMed2004

Evolution of the mannose-binding lectin gene in primates.

The mannose-binding lectin MBL2 plays an important role in the innate immune system. It binds carbohydrates surface, acts as an opsonin and activates the complement system. With the aim of studying the evolution of the MBL2 gene in primates, we sequenced its coding region in 12 non-human primate species and compared them with the human sequence. We demonstrated that nucleotide and amino-acidic sequences of the MBL2 among primates are highly homologous, underlining the importance of this molecule in the defense system against pathogen invasions. In particular, in the collagen-like domain that confers the characteristic structure to MBL2 protein, the identity among primates is really high. In the carbohydrate recognition domain, we evidenced some primates' group-specific amino-acidic mutations not resulting in changes of the structure or function of this MBL2 domain. Phylogenetic analysis did not evidence any positive selective pressure in MBL2 gene among non-human primates. Our findings indicate that MBL2 is well conserved in agreement with its important role in the immune system: in non-human primates, we did not observe the same 'plasticity' of the MBL2 human gene, where a frequency of more than 1% of nucleotide variations was described in the coding and promoter regions.

Amino Acid Sequence↗

PubMed1993

Brain weight and life-span in primate species.

In haplorhine primates (tarsiers, monkeys, apes, and humans), there is a significant correlation between brain weight and maximum life-span when the effect of body size is removed. There is also a significant correlation in haplorhine primates between brain weight and female age at first reproduction. For strepsirhine primates (lorises and lemurs), there are no significant correlations between brain weight and either life-span or female reproductive age when the effect of body size is removed. This lack of correlation in strepsirhine primates may be related to the fact that these primates are nocturnal and/or natives of the island of Madagascar, both of which conditions may reduce competition for resources and predation pressure. These findings suggest that in haplorhine primates the genetic systems controlling brain growth are linked to the systems governing the life cycle so that species with longer cycles have larger brains. When the effect of body weight is removed, leaf-eating haplorhines have significantly smaller brains and shorter lives than haplorhines with other diets. Harem-living haplorhines also have significantly smaller brains and shorter life-spans than troop-living haplorhines when the effect of body weight is removed. We also sought to test the rate-of-living hypothesis by determining whether primates with basal metabolic rates that are higher than would be expected for their body size have shorter maximum life-spans than would be expected for their body size. Metabolic rate is not correlated with life-span or female age at first reproduction when the effect of body size is removed.

Adrenal Glands↗

PubMed1998

Diversity components of impending primate extinctions.

Many extant species are at risk to go extinct. This impending loss of species is likely to cause changes in future ecosystem functions. Ecological components of diversity, such as dietary or habitat specializations, can be used to estimate the impact of extinctions on ecosystem functions. As an approach to estimate the impact of future extinctions, we tested interdependency between ecological and taxonomic change based on current predictions of extinction rates in primates. We analyzed the ecological characteristics of extant primate faunas having species in various categories of endangerment of extinction and forecasted the future primate faunas as if they were paleontological faunas. Predicting future faunas combines the wealth of ecological information on living primates with large, fossil record-like changes in diversity. Predicted extinction patterns of living primates in Africa, Asia, Madagascar, and South America show that changes in ecology differ among the regions in ways that are not reducible to taxonomic measures. The ecological effects of primate extinctions are initially least severe in South America and larger in Asia and Africa. Disproportionately larger ecological changes are projected for Madagascar. The use of taxonomy as a proxy for ecology can mislead when estimating competence of future primate ecosystems.

Animals↗

PubMed2005

Molecular evolution of the primate developmental genes MSX1 and PAX9.

In primates, the craniofacial skeleton and the dentition are marked by high levels of interspecific variation. Despite this, there are few comparative species studies conducted at the molecular level to investigate this functional diversity. We have determined nucleotide sequences of MSX1 and PAX9, two developmental genes, in a sample of 27 diverse primate species in order to identify coding or regulatory variation that may be associated with phenotypic diversity. Our analyses have identified four highly conserved noncoding sequences, including one that is conserved across primates and with dogs but not with mice. Although we find that substitution rates vary significantly across MSX1 exons, comparisons of nonsynonymous and synonymous substitution rates (dN/dS) suggest that, as a whole, MSX1 and PAX9 amino acid sequences have been under functional constraint throughout primate evolution. Compared to all other primates in our sample, our analysis of exon 1 in MSX1 finds an unusual pattern of amino acid substitution for Tarsius syrichta, a member of a lineage (tarsiers) that has many unique features among primates. For example, tarsiers are the only extant primates without deciduous incisors, and MSX1 is expressed exclusively in the incisor regions during the earliest stages of dental development. Our overall results provide insight into the utility of comparative species analyses of highly conserved developmental genes and their roles in the evolution of complex phenotypes.

Amino Acid Sequence↗

PubMed1999

Sequence evolution of the CCR5 chemokine receptor gene in primates.

The chemokine receptor CCR5 can serve as a coreceptor for M-tropic HIV-1 infection and both M-tropic and T-tropic SIV infection. We sequenced the entire CCR5 gene from 10 nonhuman primates: Pongo pygmaeus, Hylobates leucogenys, Trachypithecus francoisi, Trachypithecus phayrei, Pygathrix nemaeus, Rhinopithecus roxellanae, Rhinopithecus bieti, Rhinopithecus avunculus, Macaca assamensis, and Macaca arctoides. When compared with CCR5 sequences from humans and other primates, our results demonstrate that: (1) nucleotide and amino acid sequences of CCR5 among primates are highly homologous, with variations slightly concentrated on the amino and carboxyl termini; and (2) site Asp13, which is critical for CD4-independent binding of SIV gp120 to Macaca mulatta CCR5, was also present in all other nonhuman primates tested here, suggesting that those nonhuman primate CCR5s might also bind SIV gp120 without the presence of CD4. The topologies of CCR5 gene trees constructed here conflict with the putative opinion that the snub-nosed langurs compose a monophyletic group, suggesting that the CCR5 gene may not be a good genetic marker for low-level phylogenetic analysis. The evolutionary rate of CCR5 was calculated, and our results suggest a slowdown in primates after they diverged from rodents. The synonymous mutation rate of CCR5 in primates is constant, about 1.1 x 10(-9) synonymous mutations per site per year. Comparisons of Ka and Ks suggest that the CCR5 genes have undergone negative or purifying selection. Ka/Ks ratios from cercopithecines and colobines are significantly different, implying that selective pressures have played different roles in the two lineages.

Animals↗

PubMed1995

Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores.

How brains have evolved in response to particular selection pressures is illuminated by ecological correlates of differences in brain structure among contemporary species. The focus of most comparative studies has been on the overall size of brains relative to body size, hence ignoring the ways in which selection operates on specific neural systems. Here we investigate evolutionary radiations in the size of visual and olfactory brain structures within three orders of mammals: primates, bats and insectivores. The comparative relationships within these three orders show both similarities and differences. After removal of the allometric effect of overall brain size, the sizes of different structures within each sensory modality are positively correlated in all three orders. Correlations between visual and olfactory structures, however, are negative in primates, negative but non-significant in insectivores, and positive in bats. In both primates and insectivores, nocturnal lineages tend to have larger olfactory structures than do diurnal or partly diurnal lineages, and among the primates diurnal lineages have larger striate visual cortexes. Hence the apparent trade-off between vision and olfaction in primates seems to be related to the divergence of nocturnal and diurnal forms. However, negative correlations between visual and olfactory structures were also found when nocturnal strepsirhines and diurnal haplorhines were analysed separately, suggesting that ecological variables in addition to activity timing may be significant. Indeed, there were also associations with diet: frugivory was associated with enlargements of the geniculostriate visual system in diurnal primates, enlargements of olfactory structures in nocturnal primates, and possibly enlargements of both in bats. Further ecological associations were found within insectivores: aquatic lineages had smaller olfactory structures than in their non-aquatic counterparts, and fossorial lineages had smaller optic nerves than in non-fossorial forms. We conclude that activity timing, diet and habitat have each played a role in the evolutionary radiation of mammalian sensory systems, but with varying effects in the different taxa. Some of the associations between ecology and sensory systems suggest alternative explanations for correlates of overall brain size, which have in the past commonly been interpreted in terms of selection on intelligence.

Adaptation, Biological↗

PubMed2001

Fruits, foliage and the evolution of primate colour vision.

Primates are apparently unique amongst the mammals in possessing trichromatic colour vision. However, not all primates are trichromatic. Amongst the haplorhine (higher) primates, the catarrhines possess uniformly trichromatic colour vision, whereas most of the platyrrhine species exhibit polymorphic colour vision, with a variety of dichromatic and trichromatic phenotypes within the population. It has been suggested that trichromacy in primates and the reflectance functions of certain tropical fruits are aspects of a coevolved seed-dispersal system: primate colour vision has been shaped by the need to find coloured fruits amongst foliage, and the fruits themselves have evolved to be salient to primates and so secure dissemination of their seeds. We review the evidence for and against this hypothesis and we report an empirical test: we show that the spectral positioning of the cone pigments found in trichromatic South American primates is well matched to the task of detecting fruits against a background of leaves. We further report that particular trichromatic platyrrhine phenotypes may be better suited than others to foraging for particular fruits under particular conditions of illumination; and we discuss possible explanations for the maintenance of polymorphic colour vision amongst the platyrrhines.

Animals↗