Functional divergence of the pigmentation gene melanocortin-1 receptor (MC1R) in six endemic Macaca species on Sulawesi Island.

Coat color is often highly variable within and between animal taxa. Among hundreds of pigmentation-related genes, melanocortin-1 receptor (MC1R) plays key roles in regulating the synthesis of the dark eumelanin and the red-yellow pheomelanin. The six species of macaques that inhabit Sulawesi Island diverged rapidly from their common ancestor, M. nemestrina. Unlike most macaques, Sulawesi macaques commonly have a dark coat color, with divergence in shade and color pattern. To clarify the genetic and evolutionary basis for coat color in Sulawesi macaques, we investigated the MC1R sequences and functional properties, including basal cAMP production and α-MSH-induced activity in vitro. We found fixed non-synonymous substitutions in MC1R in each species. Furthermore, we found that six species-specific variants corresponded with variation in agonist-induced and basal activity of MC1R. Inconsistent with the dark coat color, four substitutions independently caused decreases in the basal activity of MC1R in M. hecki, M. nigra, M. tonkeana, and M. ochreata. Selective analysis suggested MC1R of M. nigra and M. nigrescens underwent purifying selection. Overall, our results suggest that fixed differences in MC1R resulted in different functional characteristics and might contribute to divergence in color among the six Sulawesi macaque species.

Evolution of the bitter taste receptor TAS2R38 in colobines.

Bitter taste perception enables the detection of potentially toxic molecules and thus evokes avoidance behavior in vertebrates. It is mediated by bitter taste receptors, TAS2Rs. One of the best-studied TAS2R is TAS2R38. Phenylthiocarbamide (PTC) perception and TAS2R38 receptors vary across primate species, and this variation may be related to variation in dietary preferences. In particular, we previously found that the low sensitivity of TAS2R38s in Asian colobines likely evolved as an adaptation to their leaf-eating behavior. However, it remains unclear whether this low PTC sensitivity is a general characteristic of the subfamily Colobinae, a primate group that feeds predominantly on leaves. We performed genetic analyses, functional assays with mutant proteins, and behavioral analyses to evaluate the general characteristics of TAS2R38 in colobines. We found that PTC sensitivity is lower in TAS2R38s of African colobines than in TAS2R38s of omnivorous macaques. Furthermore, two amino acids shared between Asian and African colobines were responsible for low sensitivity to PTC, suggesting that the last common ancestor of extant colobines had this phenotype. We also detected amino acid differences between TAS2R38s in Asian and African colobines, indicating that they evolved independently after the separation of these groups.

Handedness heritability in industrialized and nonindustrialized societies.

In modern societies, there is a decreased usage of traditional weapons to settle interpersonal or inter-group disputes compared to usage in traditional societies, possibly affecting the frequency-dependent selection on the handedness polymorphism. Another societal difference is the extensive automation of hard manual labour (including agriculture) in industrialized societies, relaxing the selection for hand specialization. Thus, selection of handedness is likely to differ between traditional and modern societies. As heritability determines the relative speed of evolutionary dynamics, handedness heritability was compared between industrialized and non-industrialized societies. First, individuals were sampled from a non-industrialized area in Indonesia, where violent conflicts are relatively frequent and tribal wars have been prevalent recently. Handedness was recorded directly or indirectly for 11,490 individuals belonging to 650 independent pedigrees, and handedness heritability was estimated using a pedigree-based animal model. Second, estimates of handedness heritability derived from published sources were collected to compare heritability estimates, accounting for various confounding variables. Non-industrialized countries displayed a significantly higher heritability value (h2 = 0.56) than that of industrialized countries (h2 = 0.20). Heritability decreased with time along the twentieth century in industrialized countries, independently of the frequency of left-handedness, and independently of the method used to measure handedness. In conclusion, the data are consistent with a decrease in handedness heritability following the industrialization process and/or the associated decrease in violence using traditional weapons. The difference in heritability between industrialized and non-industrialized countries suggests that selection of handedness is thus likely to differ between traditional and modern societies.

Male Homosexual Preference: Femininity and the Older Brother Effect in Indonesia.

Male homosexual preference (MHP) is an evolutionary enigma because it is partially heritable and imposes a fertility cost. In occidental societies, homosexual men are feminized at various levels and they have more older brothers than heterosexual men. To evaluate whether femininity and the fraternal birth order (FBO) effect are universal features of MHP or not, we collected original data from homosexual men, heterosexual men, and heterosexual women from Java (Indonesia). Facial photographs were used to test whether homosexual faces are feminized when compared with heterosexual ones. We found that faces manipulated to resemble the average face of homosexual men are perceived as facially feminized, suggesting that homosexual men are facially feminized compared to heterosexual men, although a higher facial femininity was not captured by morphological analyses. Then, family data were used to detect differences in siblings' composition between homosexuals and heterosexuals. Homosexual men displayed a higher number of older brothers than heterosexual men, even when sibship size was controlled for, suggesting that the FBO effect exists in Indonesian populations. Independent of sexual orientation, men with older brothers seem more feminized than those without older brothers, consistent with the immune origin of the FBO effect. In conclusion, MHP in Indonesia is partially feminized and they have more older brothers. Such features are also associated with MHP in other cultural contexts, suggesting a cross-cultural effect of men homosexual preference. An evolutionary explanation is available for the feminizing effect, although the FBO effect remains unexplained even if proximal mechanisms start to be identified.

Functional divergence of the bitter receptor TAS2R38 in Sulawesi macaques.

ABSTRACT: Bitter perception is mediated by G protein-coupled receptors TAS2Rs and plays an important role in avoiding the ingestion of toxins by inducing innate avoidance behavior in mammals. One of the best-studied TAS2Rs is TAS2R38, which mediates the perception of the bitterness of synthetic phenylthiocarbamide (PTC). Previous studies of TAS2R38 have suggested that geographical separation enabled the independent divergence of bitter taste perception. The functional divergence of TAS2R38 in allopatric species has not been evaluated. We characterized the function of TAS2R38 in four allopatric species of Sulawesi macaques on Sulawesi Island. We found variation in PTC taste perception both within and across species. In most cases, TAS2R38 was sensitive to PTC, with functional divergence among species. We observed different truncated TAS2R38s that were not responsive to PTC in each species of Macaca nigra and M. nigrescens due to premature stop codons. Some variants of intact TAS2R38 with an amino acid substitution showed low sensitivity to PTC in M. tonkeana. Similarly, this intact TAS2R38 with PTC-low sensitivity has also been found in humans. We detected a shared haplotype in all four Sulawesi macaques, which may be the ancestral haplotype of Sulawesi macaques. In addition to shared haplotypes among Sulawesi macaques, other TAS2R38 haplotypes were species-specific. These results implied that the variation in TAS2R38 might be shaped by geographical patterns and local adaptation. OPEN RESEARCH BADGES: This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.908jf3r.

Color Perception in Protanomalous Female Macaca fascicularis.

Protanomalous females with X chromosome-linked color vision deficiency exhibit mild abnormalities, whereas dichromats show a distinct deficiency in discriminating certain color pairs. Dichromats have an advantage in detecting a textured target when it is camouflaged by red-green colors, owing to their insensitivity to these colors. However, it is not certain whether protanomalous females possess a similar advantage in breaking camouflage. Here, we introduce an animal model of dichromatic macaque monkeys and protanomalous females. We examined whether protanomalous females have the same advantage in breaking color camouflage as shown by dichromatic macaques. We also tested whether they could discriminate a certain color pair that trichromats could, where the dichromats are confused. Our experiments show that protanomalous macaques can break color camouflage, similar to dichromats, and can discriminate colors similarly to trichromats. Protanomalous females are thus thought to have the combined ecological advantages of being both trichromats and dichromats.

Three new "caecate" earthworm species from Sulawesi, Indonesia (Oligochaeta, Megascolecidae).

Three new earthworm species are described from Sulawesi, Indonesia. Two belong to the genus Pithemera Sims & Easton, 1972, namely P.suwastikai Fahri, Amaliah & Atmowidi, sp. n. and P.tadulako Fahri, Amaliah & Atmowidi, sp. n. The new species, P.suwastikai sp. n. is distinguished by a medium size (135-165 mm long, 4.5-6.5 mm diameter), four pairs of spermathecal pores in 5/6/7/8/9, 7-12 setae between male pores, no genital markings, holandry, and simple intestinal caeca. Pithemeratadulako sp. n. is recognized by a large size (217-340 mm long, 13-15 mm diameter), two pairs of spermathecal pores in 7/8/9, no setae between male pores, no genital markings, holandry, and simple intestinal caeca. Another new species, Metaphirerusydii Fahri, Amaliah & Nguyen, sp. n., is diagnosed by its large size (250-280 mm long,12-16 mm diameter), two pairs of spermathecal pores in 7/8/9, no setae between male porophores, presence of genital markings in the male region, holandry, and complex intestinal caeca. Additionally, an identification key to "caecate" species is provided to the Sulawesi's fauna.

Functional decline of sweet taste sensitivity of colobine monkeys.

For many primates, sweet taste is palatable and is an indicator that the food contains carbohydrates, such as sugars and starches, as energy sources. However, we have found that Asian colobine monkeys (lutungs and langurs) have low sensitivity to various natural sugars. Sweet tastes are recognized when compounds bind to the sweet taste receptor TAS1R2/TAS1R3 in the oral cavity; accordingly, we conducted a functional assay using a heterologous expression system to evaluate the responses of Javan lutung (Trachypithecus auratus) TAS1R2/TAS1R3 to various natural sugars. We found that Javan lutung TAS1R2/TAS1R3 did not respond to natural sugars such as sucrose and maltose. We also conducted a behavioral experiment using the silvery lutung (Trachypithecus cristatus) and Hanuman langur (Semnopithecus entellus) by measuring the consumption of sugar-flavored jellies. Consistent with the functional assay results for TAS1R2/TAS1R3, these Asian colobine monkeys showed no preference for sucrose or maltose jellies. These results demonstrate that sweet taste sensitivity to natural sugars is low in Asian colobine monkeys, and this may be related to the specific feeding habits of colobine monkeys.

Kin Selection and Male Homosexual Preference in Indonesia.

Male homosexual preference (MHP) challenges evolutionary thinking because the preference for male-male relationships is heritable, implies a fertility cost (lower offspring number), and is relatively frequent in some societies (2-6% in Western countries) for a costly trait. It has been proposed that individuals with a MHP counterbalance reproductive costs through the transfer of resources to kin, thereby improving their indirect reproduction through kin's reproductive success. This kin selection hypothesis is not supported in Western countries and Japan, although consistent evidence has been obtained in Samoa. In this study, data from Java (Indonesia) were obtained to assess the avuncular tendencies of men with contrasting sexual orientation to measure possible resource transfer. Consistent with the kin selection hypothesis, males with a homosexual orientation reported an increased willingness to transfer resources toward nephews and nieces and declared having transferred more money to nephews and nieces. We developed a method to quantitatively estimate the contribution of kin selection on inclusive reproduction associated to sexual orientation, taking into account various possible biases. Kin selection reduced the direct reproductive cost of homosexual men by 20%, so suggesting that kin selection alone is insufficient to explain the maintenance of male homosexuality. Other potential factors are discussed, as well as the limitations of the study and the social determinant operating for the expression of increased avuncular tendencies of homosexual men.

Functional characterization of the TAS2R38 bitter taste receptor for phenylthiocarbamide in colobine monkeys.

Bitterness perception in mammals is mostly directed at natural toxins that induce innate avoidance behaviours. Bitter taste is mediated by the G protein-coupled receptor TAS2R, which is located in taste cell membranes. One of the best-studied bitter taste receptors is TAS2R38, which recognizes phenylthiocarbamide (PTC). Here we investigate the sensitivities of TAS2R38 receptors to PTC in four species of leaf-eating monkeys (subfamily Colobinae). Compared with macaque monkeys (subfamily Cercopithecinae), colobines have lower sensitivities to PTC in behavioural and in vitro functional analyses. We identified four non-synonymous mutations in colobine TAS2R38 that are responsible for the decreased sensitivity of the TAS2R38 receptor to PTC observed in colobines compared with macaques. These results suggest that tolerance to bitterness in colobines evolved from an ancestor that was sensitive to bitterness as an adaptation to eating leaves.

Report on the observed response of Javan lutungs (Trachypithecus auratus mauritius) upon encountering a reticulated python (Python reticulatus).

We observed an encounter between a reticulated python (Python reticulatus) and a group of wild Javan lutungs (Trachypithecus auratus mauritius) at the Pangandaran Nature Reserve, West Java, Indonesia. A python (about 2 m in length) moved toward a group of lutungs in the trees. Upon seeing the python, an adult male and several adult female lutungs began to emit alarm calls. As the python approached, two adult and one sub-adult female jumped onto a branch near the python and began mobbing the python by shaking the branch. During the mobbing, other individuals in the group (including an adult lutung male) remained nearby but did not participate. The python then rolled into a ball-like shape and stopped moving, at which point the lutungs moved away. The total duration of the encounter was about 40 min, during which time the lutungs stopped feeding and grooming. Group cohesiveness during and after the encounter was greater than that before the encounter, indicating that lutungs adjust their daily activity in response to potential predation risk.

Identification of individual adult female Javan lutungs (Trachypithecus auratus sondaicus) by using patterns of dark pigmentation in the pubic area.

In a series of field surveys of wild Javan lutungs (Trachypithecus auratus sondaicus) conducted at Pangandaran Nature Reserve in West Java, Indonesia, from 2011 to 2012, we tried to use a method of individual identification by using individual-specific patterns of dark pigmentation in the pubic area. During the 2011 dry season, we used a digital SLR camera with a 400-mm telephoto lens to photograph the pubic area of each individual of a habituated group. These photographs were the basis for identifying 14 different adult females. During the rainy season of 2011 and the dry season of 2012, we checked the presence/absence of each of the identified individuals and found that these patterns were stable, at least during our study period. We found that two adult females and one adult female disappeared from the subject group between the first and second and between the second and third surveys, respectively, and that one adult female gave birth between the first and second surveys, but the infant had disappeared from the group between the second and third surveys. We could not confirm the validity of the method for juvenile females because of the dense white hair in their pubic areas and the fact that few individuals had clear patterns. Furthermore, we could not use this method for males because of the lack of pigmentation in the pubic area. As patterns of pigmentation in the pubic area are known to be present in other Trachypithecus species, our method can be useful for identification of individual adult females of these species, on which few individual-based behavioral studies have been conducted. Collecting individual-based behavioral data would enable us to track the presence of individuals in groups or movements between groups; determine the effects of social rank and age on within-group competition and copulation; and examine population data.

Food-snatching behavior of free-ranging Japanese macaques observed on Shodoshima Island: a preliminary report.

We investigated the characteristics of a particular food-snatching behavior in which one individual forced another's mouth open and grabbed the food, as performed by free-ranging Japanese macaques (Macaca fuscata) in Choshikei Monkey Park on Shodoshima Island, western Japan. We conducted a survey in late June 2012 and observed one of two monkey troops, comprising 214 monkeys. We recorded the age classes and sexes of the individuals who performed the snatching behavior and were snatched from, and examined the effects of provisioned food distribution and quantity on the frequency of snatching trials and success. During the survey, we recorded 747 snatching trials, of which 609 were successful, all of which were performed by seven individuals: one adult male and six adult females. The snatching behavior occurred only during provisioning. The target animals were primarily juveniles (650 trials, 578 successful), while cases in which food was snatched from adult females (93 trials, 30 successful) and subadult females (4 trials, 1 success) were less frequent. Among the juveniles, small juveniles had food snatched more frequently than large juveniles. The higher frequency of snatching trials against juveniles was likely due to their subordinate nature. Neither the distribution nor quantity of the provisioned foods had significant effects on the number of snatching trials and successes, while the time elapsed after provisioning had significant negative effects, attributed to a decrease in the number of wheat grains left within the mouth pouch of the potential target animals.

Human-specific SNP in obesity genes, adrenergic receptor beta2 (ADRB2), Beta3 (ADRB3), and PPAR γ2 (PPARG), during primate evolution.

UNLABELLED: Adrenergic-receptor beta2 (ADRB2) and beta3 (ADRB3) are obesity genes that play a key role in the regulation of energy balance by increasing lipolysis and thermogenesis. The Glu27 allele in ADRB2 and the Arg64 allele in ADRB3 are associated with abdominal obesity and early onset of non-insulin-dependent diabetes mellitus (NIDDM) in many ethnic groups. Peroxisome proliferator-activated receptor γ (PPARG) is required for adipocyte differentiation. Pro12Ala mutation decreases PPARG activity and resistance to NIDDM. In humans, energy-expense alleles, Gln27 in ADRB2 and Trp64 in ADRB3, are at higher frequencies than Glu27 and Arg64, respectively, but Ala12 in PPARG is at lower frequency than Pro12. Adaptation of humans for lipolysis, thermogenesis, and reduction of fat accumulation could be considered by examining which alleles in these genes are dominant in non-human primates (NHP). All NHP (P. troglodytes, G. gorilla, P. pygmaeus, H. agilis and macaques) had energy-thrifty alleles, Gly16 and Glu27 in ADRB2, and Arg64 in ADRB3, but did not have energy-expense alleles, Arg16, Gln27 and Trp64 alleles. In PPARG gene, all NHP had large adipocyte accumulating type, the Pro12 allele. CONCLUSIONS: These results indicate that a tendency to produce much more heat through the energy-expense alleles developed only in humans, who left tropical rainforests for savanna and developed new features in their heat-regulation systems, such as reduction of body hair and increased evaporation of water, and might have helped the protection of entrails from cold at night, especially in glacial periods.

Boundary zone between northern and southern pig-tailed macaques and their morphological differences.

Based on previous conflicting reports that the two forms of pig-tailed macaque (northern and southern) exist as separate species, subspecies, or forms, and that their boundary zone lies in Thailand, a survey of the distribution range and morphology of pig-tailed macaques in Thailand was conducted during 2003-2010. We first conducted a questionnaire survey. Questionnaires were sent to 7,410 subdistricts throughout Thailand. We then traveled to 72 of the 123 subdistricts reporting the presence of pig-tailed macaques. However, due to a lack of reports of the presence of free-ranging pig-tailed macaques living south of the Isthmus of Kra, a survey of pet pig-tailed macaques was also conducted during 16-24 September 2011. Furthermore, 35 wild northern pig-tailed macaques inhabiting northern Thailand (13°13'N, 101°03'E) were temporarily caught and their morphological characters were measured and then compared to those of the southern form captured from Sumatra, Indonesia. Although largely allopatric, the ranges of the northern and southern pig-tailed macaques in Thailand were found to have a partially sympatric boundary at the Surat Thani-Krabi depression (8-9°30'N). Morphologically, these two forms were very distinctive, with different morphological characters such as the crown patch, the white color of the triangle above the eyes, the red streak at the external rim of the eyes, pelage color, ischial callosity, tail length and carriage, facial height, and limb length in both sexes, and patterns of sex skin swelling and reddening in females. These differences in morphological characters between the northern and southern forms should help settle the problems of their taxonomy.

Gene conversion and purifying selection shape nucleotide variation in gibbon L/M opsin genes.

BACKGROUND: Routine trichromatic color vision is a characteristic feature of catarrhines (humans, apes and Old World monkeys). This is enabled by L and M opsin genes arrayed on the X chromosome and an autosomal S opsin gene. In non-human catarrhines, genetic variation affecting the color vision phenotype is reported to be absent or rare in both L and M opsin genes, despite the suggestion that gene conversion has homogenized the two genes. However, nucleotide variation of both introns and exons among catarrhines has only been examined in detail for the L opsin gene of humans and chimpanzees. In the present study, we examined the nucleotide variation of gibbon (Catarrhini, Hylobatidae) L and M opsin genes. Specifically, we focused on the 3.6~3.9-kb region that encompasses the centrally located exon 3 through exon 5, which encode the amino acid sites functional for the spectral tuning of the genes. RESULTS: Among 152 individuals representing three genera (Hylobates, Nomascus and Symphalangus), all had both L and M opsin genes and no L/M hybrid genes. Among 94 individuals subjected to the detailed DNA sequencing, the nucleotide divergence between L and M opsin genes in the exons was significantly higher than the divergence in introns in each species. The ratio of the inter-LM divergence to the intra-L/M polymorphism was significantly lower in the introns than that in synonymous sites. When we reconstructed the phylogenetic tree using the exon sequences, the L/M gene duplication was placed in the common ancestor of catarrhines, whereas when intron sequences were used, the gene duplications appeared multiple times in different species. Using the GENECONV program, we also detected that tracts of gene conversions between L and M opsin genes occurred mostly within the intron regions. CONCLUSIONS: These results indicate the historical accumulation of gene conversions between L and M opsin genes in the introns in gibbons. Our study provides further support for the homogenizing role of gene conversion between the L and M opsin genes and for the purifying selection against such homogenization in the central exons to maintain the spectral difference between L and M opsins in non-human catarrhines.

The ischial callosities of Sulawesi macaques.

Sulawesi island has a high level of endemism, including the seven species of monkey from the genus Macaca (macaques). These monkeys have a pair of sitting pads, termed ischial callosities that have diverse shapes and previously were described verbally only. Although useful, these verbal descriptions cannot fully describe shape variation and are somewhat subjective, and cannot directly be used to analyze relationships among species. Here, we report a quantitative analysis of shape of Sulawesi macaque ischial callosities using geometric morphometric tools to optimally describe shape variation and objectively reconstruct general pattern of callosity shapes. By quantification of shape variation, we compare the relationships of each Sulawesi macaque species with each other and with the two geographically neighboring macaque species, M. nemestrina and M. fascicularis, by consensus coordinates of the callosity outlines. The Sulawesi macaques have a wider degree of variation compared with M. fascicularis and M. nemestrina; variation exists in the dorsal part and in the bending of the callosity. There are three general types of callosity shape in Sulawesi macaques: oval without bending (M. tonkeana and M. maurus), oval with outward bending (M. ochreata and M. brunnescens), and oval or reniform with inward bending (M. hecki, M. nigrescens, and M. nigra). These types are congruent with their geographical distribution. The pathway of shape change may have started from oval without bending in the center and the southern peninsula, to outward bending in the southeastern species, and to oval or reniform with inward bending in the northern species.

Female long-tailed macaques with scrotum-like structure.

Female long-tailed macaques (Macaca fascicularis) living in multimale and multifemale societies show a swelling and reddening of the sexual skin around the anogenital region when they approach ovulation. These swellings are limited to the base of the tail in many local populations. We recently observed another type of sexual swelling in long-tailed macaques inhabiting localities north of the Isthmus of Kra, Thailand. This swelling was located in the inguinal region in pubertal females. These swellings develop bilaterally into a globular structure, which so strongly resembles the male scrotum that it is difficult to reliably identify an individual's sex at a distance using only the standard phenotypic features of differential presence of clitoris or scrotum. The sex of the monkeys possessing the scrotum-like swelling was examined at the chromosomal and gonadal levels by determining the presence of two sex-related genes (the SRY and the AMEL), and sex-steroid hormone levels, respectively. For chromosomal sex, polymerase chain reaction (PCR)-based assays suggested the absence of the Y-linked SRY and AMEL loci but the presence of the X-linked AMEL locus in the scrotum-like monkeys, consistent with them being XX and not XY. Plasma testosterone levels of the monkeys possessing the inguinal sex skin swelling did not differ from those of ordinary females and was significantly lower than that of subadult and adult males. However, plasma estradiol levels were higher than those of both ordinary adult males and ordinary adult females. Together, the data strongly support the suggestion that these are XX females. Indeed, most of the tissue components of the scrotum-like swelling were in fact adipose cells. Upon our latest survey in Thailand, the scrotum-like swellings were observed only in long-tailed macaques inhabiting the Indochinese region, above the Isthmus of Kra. To understand whether the scrotum-like swelling is related to geographical distribution, further study is necessary.

Advantage of dichromats over trichromats in discrimination of color-camouflaged stimuli in nonhuman primates.

Due to a middle- to long-wavelength-sensitive (M/LWS) cone opsin polymorphism, there is considerable phenotypic variation in the color vision of New World monkeys. Many females have trichromatic vision, whereas some females and all males have dichromatic vision. The selective pressures that maintain this polymorphism are unclear. In the present study we compared the performance of dichromats and trichromats in a discrimination task. We examined tri- and dichromatic individuals of two species: brown capuchin monkeys (Cebus apella) and long-tailed macaques (Macaca fascicularis). We also examined one protanomalous chimpanzee (Pan troglodytes). The subjects' task was to discriminate a circular pattern from other patterns in which textural elements differed in orientation and thickness from the background. After they were trained with stimuli of a single color, the subjects were presented with color-camouflaged stimuli with a green/red mosaic overlaid onto the pattern. The dichromatic monkeys and the protanomalous chimpanzee selected the correct stimulus under camouflaged conditions at rates significantly above chance levels, while the trichromats did not. These findings demonstrate that dichromatic nonhuman primates possess a superior visual ability to discriminate color-camouflaged stimuli, and that such an ability may confer selective advantages with respect to the detection of cryptic foods and/or predators.

Genetic mechanism and property of a whole-arm translocation (WAT) between chromosomes 8 and 9 of agile gibbons (Hylobates agilis).

C-banding analysis with 47 gibbons of the subgenus Hylobates (Hylobates) (44-chromosome gibbons) uncovered that the gibbons had a characteristic complicated C-banding pattern. The C-band pattern also revealed that a whole-arm translocation (WAT) between chromosomes 8 and 9 existed only in the species H. agilis (agile gibbon). Comprehensive consideration allows postulation that the translocation seemed to be restricted to two subspecies: H. agilis agilis (mountain agile gibbon) and H. agilis unko (lowland agile gibbon), found in Sumatra and part of the Malay Peninsula. Moreover, combined intensive analyses of C-banding and chromosome painting provided strong evidence for a plausible evolutionary pathway of chromosome differentiation of chromosomes 8 and 9. The C-banded morph 8M(t/c) seemed to be the primary type of chromosome 8 in the subgenus and to have altered into the three morphs through three pericentric inversions. The newest morph (8A(M/ci)) produced by the third inversion exchanged the long arm for chromosome 9, and subsequently constructed the WAT morphs of 8/9A(Mc/ct) and 9/8M(i/ci).