Primate spermatogenesis: new insights into comparative testicular organisation, spermatogenic efficiency and endocrine control

Owing to the close phylogenetic relationship of Platyrrhini (New World monkeys) and Catarrhini (Old World monkeys) to man, nonhuman primates are often used as models for the study of male reproductive physiology and endocrinology. This review aims at providing new data and insights into comparative primate spermatogenesis, dealing specifically with quantitative aspects of germinal epithelial organisation and germ cell production, and with the roles of gonadotrophic hormones in this process. Typically, the seminiferous epithelium is composed of specific germ cell associations (spermatogenic stages). In rodents, prosimians and most Catarrhini, tubular cross sections contain a single spermatogenic stage whereas in Platyrrhini, great apes and man multi-stage tubules are present. Since Platyrrhini represent a more basal type of primate, this spermatogenic feature must have developed convergently. The primate multi-stage tubular arrangement was previously believed to be associated with low spermatogenic efficiency. However, recent studies using new methodological approaches and comparing primate species from all taxa have revealed that multistage organisation is compatible with highly efficient spermatogenesis. In fact, meta-analysis demonstrated that the efficiency of spermatogenesis in several nonhuman primate species is comparable to that of rodents which are considered as species with highly efficient germ cell production. The duration of the spermatogenic process was not related to organisation or efficiency of spermatogenesis. Sertoli cell work load was species-specific but had no impact on germ cell numbers and on the efficiency of spermatogenesis. The gonadotrophic hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH) are the primary regulators of primate testicular function. Recent studies revealed that in New World monkeys chorionic gonadotrophin (CG)--the primate pregnancy hormone--regulates testosterone production instead of LH. Receptor studies demonstrated a dual action of the closely related hormones LH and CG in primates. It is hypothesised that following the divergence of the Platyrrhini lineage from Catarrhini, the LH/CG system evolved independently with ancestral functions of the LH/CG system retained in the neotropical taxa. In summary, key spermatogenic features are preserved across all primate taxa whereas male reproductive endocrinology features appear substantially different in the neotropical primates compared to other primate lineages.     

Resource partitioning and interspecific interactions among sympatric rain forest arboreal mammals of the Western Ghats, India

Resource partitioning in a community of diurnal arboreal mammalsconsisting of the lion-tailed macaque Macaca silenus, bonnetmacaque (BM) Macaca radiata, Nilgiri langur Semnopithecus johnii,and the Indian giant squirrel Ratufa indica of the Western Ghats,southern India, was studied. Differences in their diet, verticalstratification, food resource niche breadth, niche overlap,and behavioral interactions were examined. Resource partitioningwas through differential habitat use, resource use, and verticalstratification. Of the four species, the BM was not a residentspecies and made frequent forays into evergreen forest fromthe adjacent deciduous forest during the flowering season ofCullenia exarillata and fruiting season of Ficus microcarpa.The macaques had narrower niches, and the langur and the squirrelhad wider niches. Niche overlap was highest between the twomacaques. Overlap among the study species was particularly pronouncedduring the flowering of C. exarillata. There was significantcorrelation between niche overlap and intolerance among thestudy species. Certain species pairs showed little or no mutualintolerance despite high overlap. Cooperative interactions suchas alarm calls occurred more frequently among the resident species.Interaction matrices revealed an underlying pattern of interspecificdominance hierarchy, with the BM dominating over the other threespecies. Our study suggests that the BM do not coexist withthe other three because of high overlap with its congener andlow occurrence of cooperative interactions.     

Multiple KIR gene polymorphisms are associated with plasma viral loads in SIV-infected rhesus macaques

Innate immune mechanisms play a deterministic role in the rate of disease progression during acute infection in HIV infected humans and SIV infection of non-human primates. The role NK cells play in mediating such an effect has thus gained importance. One of the major sets of molecules that regulate NK cell function are the killer cell immunoglobulin-like molecules (KIR’s). Our laboratory has previously shown an association of KIR3DL alleles 13 and 14 with high plasma viral loads in a cohort of SIV-infected rhesus macaques. To gain a more detailed understanding of the role of KIR polymorphisms, our laboratory herein conducted studies of three additional KIR loci and show that select KIR3DH alleles appear to be more strongly associated with high plasma viral loads than KIR3DL alleles 13 and 14. In addition, we herein document the existence of additional new alleles for the KIR1D, KIR2DL4, and the KIR3DH loci.     

Primate and Dung Beetle Communities in Secondary Growth Rain Forests: Implications for Conservation of Seed Dispersal Systems

Conservation efforts are often aimed at one or a few species. However, habitat sustainability relies on ecological interactions among species, such as seed dispersal. Thus, a community-scale conservation strategy may be more valuable in some settings. We describe communities of primary (primates) and secondary (dung beetles) seed dispersers from 5 sites in the Brazilian Amazon. We estimate community biomass of these taxa and, using multivariate ordination, examine the potential for natural reforestation at each site, given the communities of seed dispersers present. Since disturbed habitat is increasingly common and increasingly the focus of conservation efforts, we also examine differences among seed disperser communities between primary forest and secondary growth at each site. Analyses of faunal biomass in different localities and habitats indicate that secondary growth receives nearly as much use by primates as primary forest; given the dominant groups of dung beetles in secondary growth, disturbed habitat should show a pattern of seed burial that is clumped and deep. Areas with high biomass of Alouatta spp. and the large nocturnal dung beetle species may have the greatest potential for natural reforestation of secondary growth particularly for large seeded species. The data suggest that knowledge of the biomass of primary and secondary dispersing fauna facilitates predictions for the likelihood of disturbed habitat to regenerate and comparisons of sites in broader geographical areas e.g., Neotropical vs. Paleotropical forests.     

Arterial vascularization of the mandible and maxilla of neotropical primates

The objective of the present investigation was to conduct a comparative macroscopic study of the arterial vascularization of the mandible and maxilla of neotropical primates of the genera Cebus, Alouatta, Callithrix, and Leontopithecus. After vinyl was injected into the arterial system of the head of each specimen, the pieces were macerated and corroded. The level of the bifurcation of the common carotid artery into the internal and external carotids varied between the first and third cervical vertebrae. The external carotid artery accounts for most of the vascularization of the facial structures. The actual vessels responsible for the supply of this region are the sublingual, facial, angular, lingual, submandibular, submental, inferior and superior labial, maxillary, inferior alveolar, infraorbital, superior posterior alveolar, palatine major, and sphenopalatine arteries. We conclude that although the arterial vascular pattern was similar in all the genera studied, and resembles the human pattern, there are notable variations in the vasculature of the mandible and maxilla among these four neotropical genera.     

Rarity in the tropics: biogeography and macroecology of the primates

Aim To describe rarity and elucidate its biology in a tropical mammalian order, the Primates. Location Africa, Central and South America, Asia, Madagascar. Methods A review of the literature, with some additional analyses using data from the literature. A variety of definitions of rarity are used in order to describe it and to investigate its biology by correlating the degree of rarity with a variety of biological traits indicative of resource use (e.g. size of annual home range), reproductive rate (e.g. birth interval)and specialization (e.g. number of habitat types used). Results Few primate taxa occur outside the tropics, and most taxa are rare (small geographical range size or latitudinal extent, low density or both). Latitudinal extent is narrower at lower latitudes in Africa and Asia, but the potential resultant packing of taxa appears not to explain the taxonomic diversity gradient. Whilst primate species do not show the common, positive density by range size relationship, primate genera show a significant shallow slope, and primate families/subfamilies a strongly positive slope. Rare taxa are specialized, but neither use more resources nor breed more slowly than common taxa. The correlation of rarity and specialization is via geographical range: taxa with small ranges, or small ranges for their density, are specialized, but not taxa at low density. Common taxa are generalized because they consist of more differently specialized subtaxa, not because each subtaxon is generalized. Main conclusions Most primate taxa are rare, in which case most are presumably likely to go extinct. Rare primates are specialized, but do not necessarily use more resources, nor breed more slowly. Specialization as an explanation for rarity appears to work via constriction of range size, not of density. Common primates might be common (large range size) not because subtaxa or individuals are generalized, but because they are composed of more subtaxa. A consequence could be that persistence of even common taxa will depend on conservation of several populations scattered across the taxon's geographical range.     

Fetal ultrasonography: biometric data from four African primate species

BACKGROUND: Nonhuman primates are raised in large numbers in research centers and zoos. Reproductive monitoring is required to improve breeding performances. Ultrasonography is a safe method to determine gestational age and to estimate the date of parturition. However only few data are available in nonhuman primates. METHODS: Fetal biometric data were obtained throughout pregnancy on four African primate species, namely chimpanzee, gorilla, mandrill and patas monkey. Measurements included biparietal diameter, transverse abdominal diameter, femur and humerus length, external interorbital diameter, and fetal heart rate. Curves established from these data were compared with previously published data in chimpanzees and gorillas and with those for humans and other closely related primate species. RESULTS: The curves for the different hominids were very similar, while those for mandrills more closely resembled baboons and data for patas monkeys were comparable to those for macaques. CONCLUSIONS: These data, by providing a tool to evaluate precise gestational age, will be useful for centers raising these four primate species.     

Social tolerance in a despotic primate: co-feeding between consortship partners in rhesus macaques

Food sharing among nonkin-one of the most fascinating cooperative behaviors in humans-is not widespread in nonhuman primates. Over the past few years, a large body of work has investigated the contexts in which primates cooperate and share food with unrelated individuals. This work has successfully demonstrated that species-specific differences in temperament constrain the extent to which food sharing emerges in experimental situations, with despotic species being less likely to share food than tolerant ones. However, little experimental work has examined the contexts that promote food sharing and cooperation within a species. Here, we examine whether one salient reproductive context-the consortship dyad-can allow the necessary social tolerance for co-feeding to emerge in an extremely despotic species, the rhesus macaque (Macaca mulatta). We gave naturally formed male-female rhesus macaque pairs access to a monopolizable food site in the free-ranging population at Cayo Santiago, Puerto Rico. Using this method, we were able to show that tolerated co-feeding between unrelated adults can take place in this despotic species. Specifically, our results show that consort pairs co-fed at the experimental food site more than nonconsort control pairs, leading females to obtain more food in this context. These results suggest that co-feeding is possible even in the most despotic of primate species, but perhaps only in contexts that specifically promote the necessary social tolerance. Researchers might profit from exploring whether other kinds of within-species contexts could also generate cooperative behaviors.     

Brief communication: Paleobiological inferences on the locomotor repertoire of extinct hominoids based on femoral neck cortical thickness: The fossil great ape hispanopithecus laietanus as a test-case study

The relationship between femoral neck superior and inferior cortical thickness in primates is related to locomotor behavior. This relationship has been employed to infer bipedalism in fossil hominins, although bipeds share the same pattern of generalized quadrupeds, where the superior cortex is thinner than the inferior one. In contrast, knuckle‐walkers and specialized suspensory taxa display a more homogeneous distribution of cortical bone. These different patterns, probably related to the range of movement at the hip joint and concomitant differences in the load stresses at the femoral neck, are very promising for making locomotor inferences in extinct primates. To evaluate the utility of this feature in the fossil record, we relied on computed tomography applied to the femur of the Late Miocene hominoid Hispanopithecus laietanus as a test‐case study. Both an orthograde body plan and orang‐like suspensory adaptations had been previously documented for this taxon on different anatomical grounds, leading to the hypothesis that this fossil ape should display a modern ape‐like distribution of femoral neck cortical thickness. This is confirmed by the results of this study, leading to the conclusion that Hispanopithecus represents the oldest evidence of a homogeneous cortical bone distribution in the hominoid fossil record. Our results therefore strengthen the utility of femoral neck cortical thickness for making paleobiological inferences on the locomotor repertoire of fossil primates. This feature would be particularly useful for assessing the degree of orthograde arboreal locomotor behaviors vs. terrestrial bipedalism in putative early hominins. Am J PhyAnthropol 2012. © Wiley Periodicals, Inc.