Positive clinical experience with paromomycin sulfate in treatment of Balantioides coli (=Balantidium coli) natural infection in zoo-kept Mandrill monkeys (Mandrillus sphinx) and Western lowland gorillas (Gorilla gorilla gorilla).

Balantioides coli (=Balantidium coli), a large ciliated protozoan, is reported in multiple free-ranging and captive primate species, often in association with a clinical presentation that requires medical intervention. This report describes the clinical effectiveness of paromomycin sulfate against B.coli in zoo-kept mandrill monkeys (Mandrillus sphinx, at orally doses of 8-31 mg/kg, once daily (SID) for 7 days) and gorillas (Gorilla gorilla gorilla, at orally doses of 1.4-3.1 mg/kg, SID for 5 days).

Stillbirth of a mandrill (Mandrillus sphinx) in the wild: perinatal behaviors and delivery sequences.

Birth is a fundamental event in the life of animals, including our own species. More reports of wild non-human primate births and stillbirths are thus needed to better understand the evolutionary pressures shaping parturition behaviors in our lineage. In diurnal non-human primates, births generally occur at night, when individuals are resting. Consequently, they are difficult to observe in the wild and most of the current knowledge regarding perinatal behaviors comes from rare daytime births. Information about stillbirths is even rarer and their proximate causes are generally unknown. Here, we present detailed observations of a daytime birth of a stillborn wild mandrill (Mandrillus sphinx). During this event, which lasted an entire day, we recorded the behaviors of the parturient female ad libitum, using video recordings and photos. The 5-year-old female was primiparous and of low dominance rank. The length of her pregnancy was shorter than usual and the partum phase was extremely long compared to other birth reports in non-human primates. The female disappeared shortly after this event and was assumed to have died. We discuss the possible causes of this stillbirth including the infant's presentation at birth and maternal inexperience.

Emotional states following grooming in female mandrills.

Grooming is a common cooperative behavior whose exact costs and benefits are still to be fully elucidated. In this study, we evaluated the emotional consequences of giving and receiving grooming in mandrills (Mandrillus sphinx), and how these may change along time after the termination of grooming. We used scratching as a behavioral indicator of anxiety-like emotions. Groomees showed increased scratching immediately after the termination of grooming, while in the subsequent minutes scratching decreased below baseline. The initial increase was larger after longer grooming events, suggesting it represented a case of postinhibitory rebound. The subsequent decline in scratching rates was larger after grooming received by a kin, suggesting interactions with kin are particularly relaxing. Scratching rates shown by groomers were unaffected by grooming interactions. These results highlight that the emotional states following grooming can have a complex time course, and may contribute to explain the inconsistencies found in the previous literature.

Record of thanatology and cannibalism in drills (Mandrillus leucophaeus).

Comparative thanatology includes the scientific study of death in non-human animals, which involves emotional, social, and exploratory responses of individuals and groups towards corpses. Stillborn babies and dead infants often elicit maternal and alloparental care that can persist for days, weeks, or even months, especially in primates. After this period, cannibalistic acts can occur not only by groupmates but also by the mother. Such cannibalism has been reported both in captive and wild primate groups, suggesting that the phenomenon is evolutionary adaptive. Here, we report a case in drills (Mandrillus leucophaeus), a largely unstudied monkey species. We collected data from the birth to the death of the infant on maternal and alloparental care towards the newborn across three phases: pre-mortem, post-mortem, and post-mortem cannibalism. The mother maintained high levels of grooming after the infant's death. Both the mother and other group members interacted with the dead baby by trying to engage its gaze. Two days after the death, the mother started to eat the corpse until it was almost completely consumed; there was no sharing with other group members. Although we cannot draw firm conclusions about potential benefits of the mother's behavior, this observation on drills adds a piece to the puzzle of thanatological behaviors and cannibalism in primates.

Mother-to-daughter transmission of hygienic anti-parasite behaviour in mandrills.

Social animals are particularly exposed to infectious diseases. Pathogen-driven selection pressures have thus favoured the evolution of behavioural adaptations to decrease transmission risk such as the avoidance of contagious individuals. Yet, such strategies deprive individuals of valuable social interactions, generating a cost-benefit trade-off between pathogen avoidance and social opportunities. Recent studies revealed that hosts differ in these behavioural defences, but the determinants driving such inter-individual variation remain understudied. Using 6 years of behavioural and parasite data on a large natural population of mandrills (Mandrillus sphinx), we showed that, when parasite prevalence was high in the population, females avoided grooming their conspecifics' peri-anal region (PAR), where contagious gastro-intestinal parasites accumulate. Females varied, however, in their propensity to avoid this risky body region: across years, some females consistently avoided grooming it, while others did not. Interestingly, hygienic females (i.e. those avoiding the PAR) were less parasitized than non-hygienic females. Finally, age, dominance rank and grooming frequency did not influence a female's hygiene, but both mother-daughter and maternal half-sisters exhibited similar hygienic levels, whereas paternal half-sisters and non-kin dyads did not, suggesting a social transmission of this behaviour. Our study emphasizes that the social inheritance of hygiene may structure behavioural resistance to pathogens in host populations with potential consequences on the dynamics of infectious diseases.

Identification of potentially zoonotic parasites in captive orangutans and semi-captive mandrills: Phylogeny and morphological comparison.

Cysts and trophozoites of vestibuliferid ciliates and larvae of Strongyloides were found in fecal samples from captive orangutans Pongo pygmaeus and P. abelii from Czech and Slovak zoological gardens. As comparative material, ciliates from semi-captive mandrills Mandrillus sphinx from Gabon were included in the study. Phylogenetic analysis of the detected vestibuliferid ciliates using ITS1-5.8s-rRNA-ITS2 and partial 18S ribosomal deoxyribonucleic acid (rDNA) revealed that the ciliates from orangutans are conspecific with Balantioides coli lineage A, while the ciliates from mandrills clustered with Buxtonella-like ciliates from other primates. Morphological examination of the cysts and trophozoites using light microscopy did not reveal differences robust enough to identify the genera of the ciliates. Phylogenetic analysis of detected L1 larvae of Strongyloides using partial cox1 revealed Strongyloides stercoralis clustering within the cox1 lineage A infecting dogs, humans, and other primates. The sequences of 18S rDNA support these results. As both B. coli and S. stercoralis are zoonotic parasites and the conditions in captive and semi-captive settings may facilitate transmission to humans, prophylactic measures should reflect the findings.

Mandrill mothers associate with infants who look like their own offspring using phenotype matching.

Behavioral discrimination of kin is a key process structuring social relationships in animals. In this study, we provide evidence for discrimination towards non-kin by third-parties through a mechanism of phenotype matching. In mandrills, we recently demonstrated increased facial resemblance among paternally related juvenile and adult females indicating adaptive opportunities for paternal kin recognition. Here, we hypothesize that mandrill mothers use offspring's facial resemblance with other infants to guide offspring's social opportunities towards similar-looking ones. Using deep learning for face recognition in 80 wild mandrill infants, we first show that infants sired by the same father resemble each other the most, independently of their age, sex or maternal origin, extending previous results to the youngest age class. Using long-term behavioral observations on association patterns, and controlling for matrilineal origin, maternal relatedness and infant age and sex, we then show, as predicted, that mothers are spatially closer to infants that resemble their own offspring more, and that this maternal behavior leads to similar-looking infants being spatially associated. We then discuss the different scenarios explaining this result, arguing that an adaptive maternal behavior is a likely explanation. In support of this mechanism and using theoretical modeling, we finally describe a plausible evolutionary process whereby mothers gain fitness benefits by promoting nepotism among paternally related infants. This mechanism, that we call 'second-order kin selection', may extend beyond mother-infant interactions and has the potential to explain cooperative behaviors among non-kin in other social species, including humans.

Advenella mandrilli sp. nov., a bacterium isolated from the faeces of Mandrillus sphinx.

A novel Gram-negative strain WQ 585T, isolated from the faeces of mandrills (Mandrillus sphinx) collected at Yunnan Wild Animal Park, Yunnan province, China, was subjected to a polyphasic taxonomic study. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate belongs to the genus Advenella, sharing 98.5% and 98.2% sequence similarity with the type strain Advenella alkanexedens LAM0050T and Advenella faeciporci M-07T, respectively. The predominant ubiquinone was Q-8. The major cellular fatty acids (> 10%) were C16:0, C17:0 cyclo and Summed Feature 2. The G + C content of the genomic DNA of strain WQ 585T was 49.0%. The whole genome average nucleotide identity (gANI) values of strain WQ 585T with strain A. alkanexedens LAM0050T and A. faeciporci M-07T were 86.7% and 86.7%, and the digital DNA-DNA hybridization values of strain WQ 585T with strain A. alkanexedens LAM0050T and A. faeciporci M-07T were 64.5% and 62.5%, respectively. Growth occurred at 10-45 °C (optimally at 20-30 °C), pH 6.0-9.0 (optimally at pH 7.0), and 0-5% (w/v) NaCl (optimally at 0.5-2.0%). On the basis of the taxonomic evidence, a novel species, Advenella mandrilli sp. nov., is proposed. The type strain is WQ 585T (= KCTC 82396 T = CCTCC AA 2020028 T).

Colour Preferences in Relation to Diet in Chimpanzees(Pan troglodytes), Gorillas (Gorilla gorilla) and Mandrills (Mandrillus sphinx).

Although trichromatic colour vision has been extensively studied as it grants significant advantages for Old World primates, it is unknown which selective pressures were behind the trait's evolution. The leading hypothesis would be that colour vision arose as a foraging adaptation because it allowed individuals to spot food more efficiently. To test this, we exposed 3 chimpanzees (Pan troglodytes), 5 gorillas (Gorilla gorilla) and 3 mandrills (Mandrillus sphinx) to colour cardboard plates to assess whether colours related to diet were the most preferred. The experimental setting was divided into two phases. During the first, animals were provided with colour cardboard plates of only 1 colour per data collection session. The order of colour presentation was randomly determined: white, black, yellow, green and red. In phase 2, primates were simultaneously provided with cardboard plates of all colours. Behavioural interactions with plates were measured using a one-zero group focal sampling (10-s sampling intervals and 20-min observation periods). Results showed that when animals were exposed to only 1 colour at a time, they exhibited different colour preferences depending on the species considered. Chimpanzees preferred red and yellow, the colours linked to fruits, while gorillas selected red and white. Mandrills exhibited fewer differences between colour preferences, with red being the most selected. Furthermore, when all colours were simultaneously provided, individuals chose colours related to diet over black and white. Although there were clear individual differences, our results support that trichromatic colour vision is an advantage in detecting and selecting red items. In the wild, it could be important in the detection of reddish fruits and leaves.

High level of intrinsic phenotypic antimicrobial resistance in enterobacteria from terrestrial wildlife in Gabonese national parks.

Data on the prevalence of antibiotic resistance in Enterobacteriaceae in African wildlife are still relatively limited. The aim of this study was to estimate the prevalence of phenotypic intrinsic and acquired antimicrobial resistance of enterobacteria from several species of terrestrial wild mammals in national parks of Gabon. Colony culture and isolation were done using MacConkey agar. Isolates were identified using the VITEK 2 and MALDI-TOF methods. Antibiotic susceptibility was analysed and interpreted according to the European Committee on Antimicrobial Susceptibility Testing guidelines. The preliminary test for ESBL-producing Enterobacteriaceae was performed by replicating enterobacterial colonies on MacConkey agar supplemented with 2 mg/L cefotaxime (MCA+CTX). Extended-spectrum beta-lactamase (ESBL) production was confirmed with the double-disc synergy test (DDST). The inhibition zone diameters were read with SirScan. Among the 130 bacterial colonies isolated from 125 fecal samples, 90 enterobacterial isolates were identified. Escherichia coli (61%) was the most prevalent, followed by Enterobacter cloacae (8%), Proteus mirabilis (8%), Klebsiella variicola (7%), Klebsiella aerogenes (7%), Klebsiella oxytoca (4%), Citrobacter freundii (3%), Klebsiella pneumoniae (1%) and Serratia marcescens (1%). Acquired resistance was carried by E. coli (11% of all E. coli isolates) and E. cloacae (3% of all E. cloacae) isolates, while intrinsic resistance was detected in all the other resistant isolates (n = 31); K. variicola, K. oxytoca, K. pneumoniae, E. cloacae, K. aerogenes, S. marcescens and P. mirabilis). Our data show that most strains isolated in protected areas in Gabon are wild type isolates and carry intrinsic resistance rather than acquired resistance.

Dental microstructure records life history events: A histological study of mandrills (Mandrillus sphinx) from Gabon.

Accentuated lines in dental microstructure are hypothesized to correlate with potentially stressful life history events, but our understanding of when, how and why such accentuated lines form in relation to stressful events is limited. We examined accentuated line formation and life history events in the teeth of three naturally deceased mandrills (Mandrillus sphinx, Cercopithecidae), for whom we had detailed life history information. We determined the ages at formation of accentuated lines in histological tooth sections and used dates of birth and death to calibrate dental histology to calendar time and individual age. We found accentuated lines that matched their mother's resumption of sexual cycles in two individuals, and possibly in the third individual. The subjects also formed lines when their mothers were mate-guarded by males or wounded. Accentuated lines matched the birth of the next sibling in one of two cases. Both females formed accentuated lines when they experienced their own sexual swelling cycles, but lines did not match all sexual swelling cycles. Mate-guarding matched an accentuated line in one case, but not in another. Lines matched all three parturitions in the two females. Changes in alpha male and captures did not consistently coincide with accentuated line formation, but repeated captures were associated with lines. Using simulated data, we show that the observed number of matches between lines and events would be very unlikely under a null hypothesis of random line formation. Our results support the hypothesis that some life history events are physiologically stressful enough to cause accentuated line formation in teeth. They contribute to our understanding of how primate life histories are recorded during dental development and enhance our ability to use teeth to reconstruct life history in the absence of direct observation.

Mandrills learn two-day time intervals in a naturalistic foraging situation.

Primates display high efficiency in finding food in complex environments. Knowledge that many plant species produce fruit simultaneously, can help primates to anticipate fruit finding at the start of fruiting seasons. Knowledge of elapsed time can help primates decide when to revisit food trees to find ripened fruit and to return before competitors find these fruits. To investigate whether mandrills are able to learn time intervals of recurring food, we recorded the foraging choices of captive mandrills in a group setting. We used a procedure with renewable food rewards that could be searched for: carrots and grapes, hidden underground in specific places with different renewal intervals (2 and 5 days, respectively). We monitored the first choice of location for individuals, if other individuals had not already searched at the same location, to exclude possible effects of individuals following others rather than relying on memory. Throughout the study, the mandrills became increasingly likely to first search at carrot locations on carrot days, while the probability of them searching at carrot locations decreased on days without carrot. Due to model instability, our results were inconclusive about an effect of grape days on the choice of the mandrills. Cues provided by conspecifics indicating the availability of simultaneously emerging food rewards did not affect the choice of the mandrills. We conclude that mandrills can take into account elapsed time in a foraging context. Thereby, this study indicates how mandrills can use temporal cognitive abilities to overcome temporal challenges of food-finding in a group setting.

Natural infection of free-ranging mandrills (Mandrillus sphinx) by enteroviruses and astroviruses in southern Gabon.

Enteroviruses (Picornaviridae) and astroviruses (Astroviridae) cause various diseases in humans and animals, including in non-human primates (NHPs). Some enteroviruses and astroviruses detected in NHPs are genetically related to those infecting humans, indicating the occurrence of interspecies transmissions. In this study, we screened 200 fecal samples of 56 free-ranging mandrills (Mandrillus sphinx) by nested reverse transcription-PCR with primers targeting the VP1 and RdRp genes, to evaluate the diversity of enterovirus and astrovirus infection, respectively, and the associated zoonotic risk. Overall, ten samples from six mandrills were enterovirus-positive (5%), and three samples from three mandrills were astrovirus-positive (1.5%). This is the first evidence of astrovirus infection in mandrills. Phylogenetic analyses based on the VP1 sequences revealed that all ten enterovirus sequences were part of the species Enterovirus J, suggesting low zoonotic risk. Phylogenetic analysis of the three astrovirus sequences showed that they all belonged to the Mamastrovirus genus. Two astrovirus sequences were highly divergent from all human astrovirus sequences (63.4-73% nucleotide identity), while one sequence (AstV-5) suggested cross-species transmission from humans to mandrills. Additional studies are needed to better characterize the identified astroviruses and to confirm whether mandrills are host of astroviruses than can be transmitted to humans.

Comparative performance of orangutans (Pongo spp.), gorillas (Gorilla gorilla gorilla), and drills (Mandrillus leucophaeus), in an ephemeral foraging task.

A goal of the comparative approach is to test a variety of species on the same task. Here, we examined whether the factors that helped capuchin monkeys improve their performance in a dichotomous choice task would generalize to three other primate species: orangutans, gorillas, and drill monkeys. In this task, subjects have access to two options, each resulting in an identical food, but one (the ephemeral option) is only available if it is chosen first, whereas the other one (the permanent option) is always available. Therefore, the food-maximizing solution is to choose the ephemeral option first, followed by the permanent option for an additional reward. On the original version (plate task), the options were discriminated by the color and pattern of the plates holding the food, while on two subsequent versions we used altered cues that we predicted would improve performance: (1) the color of the foods themselves (color task), which we hypothesized was relevant to primates, who choose foods rather than substrates on which foods are found when foraging, and (2) patterned cups covering the foods (cup task), which we hypothesized would help primates avoid the prepotent response associated with visible food. Like capuchins, all three species initially failed to solve the plate task. However, while orangutans improved their performance from the plate to the color task, they did not for the cup task, and only a few gorillas and no drills succeeded in either task. Unfortunately, our ability to interpret these data was obscured by differences in the subjects' level of experience with cognitive testing and practical constraints that precluded the use of completely identical procedures across species. Nonetheless, we consider what these results can tell us, and discuss the value of conducting studies across multiple sites despite unavoidable differences.

Análisis del impacto ergonômico asociado a la manipulación de cargas en trabajadores de equipos de perforación del sector petrolero / Analysis of the ergonomie impact associated with cargo handling in drilling equipment workers in the oil sector

Resumen El mundo actual y las tendencias de universalización de procesos que se dan a través de la globalización, la apertura de mercados, la internacionalización, la competencia y todas las nuevas situaciones que el desarrollo empresarial trae día a día hacen que los procesos empresariales deban ser más eficientes y eficaces, con lo cual existen riesgos asociados con las actividades que implican un sobre esfuerzo físico y por ende una posible lesión osteomuscular. Objetivo. Analizar las relaciones existentes entre las tareas de impacto negativo y las variables ergonómicas asociadas a la manipulación de cargas, a través del uso de las herramientas de evaluación REBA y RULA de manera que se identifiquen los factores de riesgo por parte de los trabajadores de Drilling & Well Services, especialmente cuñeros y encuelladores de una empresa petrolera. Materiales y métodos. La investigación es de tipo descriptivo, pues representa un análisis experimental que tiene como objetivo establecer las condiciones iniciales y determinar la manera como se manifiesta una determinada circunstancia particular identificando los rasgos característicos de la operación. Resultados. Se evidenciaron actividades como el levantar y posicionar la cuña, trasladar la tubería de perforación, soltar o ajustar las llaves de potencia y ajustar los brazos de los elevadores para cerrarlos y con ello asegurar la tubería de perforación, como las acciones de riesgo más importantes en las operaciones de los cuñeros y operadores.

Abstract The current world and the tendencies of universalization of processes that occur through globalization, the opening of markets, internationalization, competition and all the new situations that business development brings every day make processes must be more efficient and risks, with which there are risks associated with activities that involve physical exertion and therefore a possible musculoskeletal injury. Objective. Analyze the relationships identified between the negative impact tasks and the ergonomic variables associated with cargo handling, by using the REBA and RULA assessment tools so that risk factors are identified by Drilling & Well workers Services, especially wedges and pollsters of an oil company. Materials and methods. The research is descriptive, since it represents an experimental analysis that aims to establish the initial conditions and determine the way in which a particular circumstance is manifested by identifying the characteristic features of the operation. Results. There were activities such as lifting and positioning the wedge, moving the drill pipe, releasing or adjusting the power keys and adjusting the arms of the elevators to close and with it controlling the drill pipe, as the most important risk actions in the operations of the wedges and operators.

Seasonality and interindividual variation in mandrill feeding ecology revealed by stable isotope analyses of hair and blood.

Mandrills are large-bodied terrestrial forest primates living in particularly large social groups of several hundred individuals. Following these groups in the wild to assess differences in diet over time as well as among individuals is demanding. We here use isotope analyses in blood and hair obtained during repeated captures of 43 identified free-ranging mandrills (Mandrillus sphinx) from Southern Gabon, to test how dietary variation relates to the season as well as an individual's age and sex. We measured the stable carbon (δ13 C‰) and nitrogen (δ15 N‰) isotope ratios in 46 blood and 214 hair section samples as well as from a small selection of mandrill foods (n = 24). We found some seasonal isotopic effects, with lower δ13 C values but higher δ15 N values observed during the highly competitive long dry season compared to the fruit-rich long rainy season. Variation in δ13 C was further predicted by individual age, with higher δ13 C values generally found in younger individuals suggesting that they may consume more high canopy fruit than older individuals, or that older individuals consume more low canopy foliage. The best predictor for δ15 N values was the interaction between age and sex, with mature and reproductively active males revealing the highest δ15 N values, despite the observation that males consume substantially less animal food items than females. We interpret high δ15 N values in these mature male mandrill blood and hair sections to be the result of nutritional stress associated with intense male-male competition, particularly during mating season. This is the first study showing isotopic evidence for nutritional stress in a free-ranging primate species and may spark further investigations into male mandrill diet and energy balance.

Conflict over grooming topography between mandrill groomers and groomees.

Grooming directed to different body areas is likely to imply different costs and benefits for groomers and groomees. In this study, we investigated social influences on grooming topography in captive female mandrills (Mandrillus sphinx). Subordinate groomers preferred to direct grooming to "safe" areas (the back and rump) compared to dominant groomers, while subordinate groomees did not solicit preferentially grooming to safe areas. Groomers tended to initiate grooming episodes from safe areas, while groomees solicited the switch to unsafe areas. Our results highlight a previously unrecognized source of conflict between the partners of grooming, one of the most common cooperative interactions in animals.

Microdrill in endoscopic stapes surgery: Is it safe?

PURPOSE: To assess the safety of using a microdrill in endoscopic vs microscopic stapes surgery. MATERIALS AND METHODS: A retrospective review of 29 adult ears with otosclerosis who underwent either an endoscopic or microscopic approach to microdrill stapedotomy. PRIMARY OUTCOME: Determine if transcanal endoscopic stapes surgery with the microdrill is as safe as microscopic stapes surgery. Secondary outcome: Bone and air pure-tone averages, air-bone gap, speech discrimination, overall surgical cost, and operative time were measured and analyzed. Complications such as post-operative dysgeusia, vertigo, readmission, revision and hearing loss were noted. RESULTS: 29 patients with otosclerosis were retrospectively reviewed, in total 14 endoscopic and 15 microscopic approaches were included, all performed over one-year period. None of the endoscopic surgeries require conversion to the microscope. No statistically significant audiometric differences between the endoscopic vs microscopic approaches in air pure-tone averages and air-bone gap. There were 82.8% air-bone gap closure to <15 dB with no significant difference in the percent of such closures between the endoscopic (85.7%) and microscopic groups (80%, P = .68). Three prostheses were used: 4.25 mm (17.2%), 4.5 mm (58.6%) and the 4.75 mm (24.1%) smart/eclipse. Endoscopic median operative time was 51 min vs 42 min for microscopic approach (P =.004). CONCLUSIONS: The endoscopic with microdrill approach is criticized to lack depth perception, especially when using a microdrill to perform in stapedotomies. Our study showcases that using the microdrill use produces minimal differences in outcomes, cost, and is a safe modality to stapes surgery in both approaches.

Same father, same face: Deep learning reveals selection for signaling kinship in a wild primate.

Many animals rely on facial traits to recognize their kin; however, whether these traits have been selected specifically for this function remains unknown. Using deep learning for face recognition, we present the first evidence that interindividual facial resemblance has been selected to signal paternal kinship. Mandrills (Mandrillus sphinx) live in matrilineal societies, in which females spend their entire lives not only with maternal half-sisters (MHS) but also with paternal half-sisters (PHS). We show that PHS have more differentiated social relationships compared to nonkin, suggesting the existence of kin recognition mechanisms. We further demonstrate that facial resemblance increases with genetic relatedness. However, PHS resemble each other visually more than MHS do, despite both kin categories sharing similar degrees of genetic relatedness. This paternally derived facial resemblance among PHS indicates selection to facilitate kin recognition. This study also highlights the potential of artificial intelligence to study phenotypic evolution.

Odontochronologies in male and female mandrills (Mandrillus sphinx) and the development of dental sexual dimorphism.

OBJECTIVES: We examine how dental sexual dimorphism develops in mandrills, an extremely sexually dimorphic primate. We aimed to (a) establish the chronology of dental development (odontochronology) in male and female mandrills, (b) understand interindividual and intersex variation in odontochronologies, and (c) determine how dental sexual dimorphism is achieved. MATERIALS AND METHODS: We prepared histological ground sections from the permanent teeth of four female and four male mandrills from the semi-free ranging colony at the Centre International de Recherches Médicales, Franceville, Gabon. We used the microscopic growth increments in the sections to create odontochronologies. We compared ages at crown initiation, crown formation times (CFT) and crown extension rates (CER) between individuals and sexes to assess interindividual and intersex variation. RESULTS: All mandrill teeth are sexually dimorphic in size. Dental sexual dimorphism in mandrills is achieved via sex differences in the duration of growth (bimaturism) and in growth rates. We also found interindividual and intersex variation in the ages at initiation and completion of crown formation. DISCUSSION: Our results show that the rate of ameloblast differentiation varies between individuals and that selection for both the age at tooth initiation and CER has occurred independently in males and females to ensure that the teeth develop at appropriate times relative to the growth of the sexually dimorphic jaws. They also show that canine dimorphism is achieved through differences in both CER and CFT, unlike extant great apes or Cantius. Given at least three mechanisms for achieving canine dimorphism, we need more information to trace the evolution of this trait in primates.