Publications by authors named "Gilissen E"
The field of phenomics is experiencing unprecedented advances thanks to the rapid growth of morphological quantification based on three-dimensional (3D) imaging, online data repositories, team-oriented collaborations, and open data-sharing policies. In line with these progressions, we present an extensive primate phenotypic dataset comprising >6,000 3D scans (media) representing skeletal morphologies of 386 individual specimens covering all hominoid genera (except humans) and other selected primates. The digitized specimens are housed in physical collections at the American Museum of Natural History, the National Museum of Natural History, the Royal Museum for Central Africa (Belgium), the Cleveland Museum of Natural History, and Stony Brook University.
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- - The study investigates how ecology and social factors influence cognitive skills in primates by examining the size of specific brain regions related to metacognition and working memory in 16 primate species.
- - Researchers found the volume of the frontal pole (FP) and dorso-lateral prefrontal cortex (DLPFC) is significantly related to body size, daily travel distance, and population density, indicating both ecological and social constraints play a role in cognitive evolution.
- - The results suggest that ecological factors primarily drive brain region size, while social factors more strongly affect the FP, highlighting the importance of foraging and social interactions in the cognitive development of primates.
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- Spotted hyaenas show notable resilience against injuries and diseases, yet understanding the pathologies they face is crucial for ecological research and conservation.
- A study of 52 spotted hyaena skulls revealed that 44% exhibited various pathologies, such as craniosynostosis, osteomyelitis, and trauma-related injuries.
- The findings enhance our understanding of hyaena health, potential conservation challenges, and provide a basis for comparing similar conditions in other apex predators.
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- The mammalian cerebral cortex is typically organized into six layers, but some areas, like the primary motor cortex, and certain species (like elephants and cetaceans) lack a clear layer 4.
- Researchers studied where thalamocortical projections, which normally target layer 4, end up in these species and discovered variations in how these projections are distributed across different cortical layers.
- The findings suggest that the absence or distinction of layer 4 has implications for how the cortex processes information and may reflect evolutionary changes in mammalian brains.
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- The study explores how the structure of the femur (thigh bone) and pelvis is coordinated with locomotion among different primate species, including humans, chimps, bonobos, and baboons.
- It utilizes geometric morphometrics to analyze the relationships and integration of pelvic and femoral morphology, revealing differences in how these species adapt to their modes of locomotion.
- Results indicate that baboons have strong morphological integration but low morpho-structural integration, while humans display the opposite, suggesting different evolutionary pressures impacting their locomotion and skeletal features.
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- * The study involved 14 experts assessing an MRI-derived endocast of a human brain to evaluate how accurately they could identify specific brain folds (sulci) based on their expertise.
- * Findings revealed significant discrepancies in experts' identifications; accuracy varied with the position on the endocast and highlighted the need to account for variations in sulcal shape when analyzing fossil specimens, which could impact interpretations in palaeoanthropology.
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- This study investigates the sexual dimorphism in cranial structures and brain characteristics of eastern lowland gorillas, focusing on both external crania and internal endocasts.
- Using CT scans and advanced 3D morphometric techniques, researchers identified significant differences in size and shape between male and female gorillas.
- Findings revealed that males have larger, more elongated features including the face and brain structures, whereas females exhibit rounder cranial formations and specific differences in the positioning of the cerebellum and olfactory bulb.
The impact of environmental factors on the evolution of brain size in carnivorans.
Commun Biol
September 2022
The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species.
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- * A study of 114 crania using 3D geometric morphometrics revealed that fluctuating asymmetry (FA) accounts for a large portion of facial shape variation in mountain gorillas, indicating underlying stress rather than simply a preference for chewing on one side.
- * Over the last century, there has been an increase in stress-related developmental instability in mountain gorillas, suggesting a decline in their health and stability as an endangered species.
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- The study investigates the little-known guenon species Cercopithecus dryas, which has an unclear taxonomic status, with some experts considering it distinct from C. salongo.
- New specimens from the TL2 region in the Congo Basin and CT scans of previous juvenile specimens allow for a detailed examination of C. dryas morphology and comparisons with C. salongo.
- Findings suggest that C. dryas and C. salongo are morphologically similar, leading researchers to propose that C. salongo should be classified as a junior synonym of C. dryas, potentially necessitating a reclassification under a different genus.
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- The study examined adult Egyptian fruit bats in three different environments: primary rainforest, subtropical woodland, and fifth-generation captivity, focusing on proliferative (Ki-67) and immature (doublecortin) cells in the dentate gyrus.
- Four methods were used to analyze the effect of the environment on these cells, with results showing that proliferative cell numbers remained consistent across groups, indicating a stable growth rate within the species.
- In contrast, immature cell counts showed variability, with wild-caught bats having more immature neurons compared to captive ones only when standardized to total granule cell numbers, suggesting that environmental impact on neuron development is dependent on the analysis technique used.
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- Researchers studied white matter interstitial cells (WMICs) in three bat species (Megaloglossus woermanni, Casinycteris argynnis, and Rousettus aegyptiacus) to understand their characteristics and populations in the mammalian brain.
- They found a significant number of WMICs across the species, with Rousettus aegyptiacus having the highest count, and identified various inhibitory neurochemical types through immunostaining techniques.
- The study indicated that while most WMIC characteristics were similar to those in other mammals, there was a notable difference in the prevalence of calbindin-reactive WMICs compared to primates, suggesting a potential relationship between WMIC numbers
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- The hippocampus has different regions with specialized roles, including CA2 which is linked to social cognition, while CA1 and CA3 relate to spatial cognition.
- Research shows that the size of the hippocampus evolves alongside factors like group size and home range in primates, but diet does not significantly affect hippocampal volume.
- There are also sex differences in hippocampal volume that correlate with body size differences, reflecting the influence of social structure and behavior on brain evolution in primates.
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- Human tauopathies are diseases characterized by the buildup of improperly modified tau proteins, resulting in neurofibrillary tangles, which contribute to neurodegeneration.
- A study on aged cats (18-21 years old) revealed that 4 out of 6 cats exhibited abnormal tau accumulation in neurons, indicating that tau pathology can develop naturally with age, independent of amyloid deposits.
- The research suggests that an enzyme called glycogen synthase kinase-3 (GSK3) may play a role in the abnormal phosphorylation of tau, linking the tau pathology in aging cats to similar processes in human tauopathies.
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- Primates depend on cognitive skills like decision-making and episodic memory to navigate complex environments and effectively forage for food.
- The study focuses on the ventromedial prefrontal cortex (VMPFC), suggesting it plays a crucial role in foraging and cognitive functions related to feeding ecology.
- Findings indicate that the size of the VMPFC is significantly associated with dietary diversity and complexity in foraging strategies across various primate species.
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- The study investigates cranial and endocranial shape variation in 14 modern species of platyrrhine primates and two extinct species, focusing on the Atelidae family, using advanced imaging and geometric morphometric techniques.
- Results show that differences in brain shape correlate with the size of specific brain regions, revealing distinct anatomical positions among different species, particularly in regards to the neocortex and brainstem.
- The findings highlight the unexpected similarities between the extinct Caipora and the modern Brachyteles, emphasizing the need to consider both current and extinct species to better understand evolutionary diversification in primates.
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- Human activities are causing a rapid decline in species and populations, leading to significant loss of genetic diversity which threatens long-term species survival.
- The study focuses on two critically endangered eastern gorilla taxa by analyzing historical and modern genetic samples to understand changes in their genetic diversity over the past century.
- Findings reveal a notable decline in genetic diversity for Grauer's gorillas, attributed to the loss of peripheral populations, highlighting the urgent need for conservation efforts to protect remaining populations.
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- The study examined adult neurogenesis in three prosimian primate species using markers to identify new neurons in their brains.
- Two species were wild-caught from Africa, while one was bred in captivity, and brain tissues were prepared for analysis.
- Key findings included evidence of new neuron production in specific brain areas, revealing both common and unique patterns of neurogenesis across the studied species.
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- The research focuses on the evolution of brain morphology in early hominins, specifically Australopithecus africanus, using advanced imaging techniques.
- It compares two specimens from South Africa, analyzing their endocranial features to understand differences between them and modern humans, as well as their similarities with chimpanzees (Pan).
- Findings highlight key contrasts, particularly in the parietal regions, and show that the brain shape of A. africanus is closer to that of chimpanzees than to modern humans, especially in the frontal gyri.
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- The study explores the nuclear organization of cholinergic, catecholaminergic, serotonergic, and orexinergic systems in the brains of the springhare and Beecroft's scaly-tailed squirrel using immunohistochemical labeling.
- It compares their brain structures to other rodents and notes that these species have larger brains than expected for their body size.
- While most of the nuclear structures were similar to those in other rodents, unique differences were found in cholinergic and catecholaminergic systems, such as specific neuron locations that had not been observed in previous studies of rodents.
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- Despite having many well-preserved skulls from South African cercopithecoids, there has been limited study on their brain structure and external morphology, although recent imaging technology offers new research opportunities.
- This study utilizes advanced X-ray microtomography to analyze the endocranial features of 14 cercopithecoid specimens and provides detailed descriptions of their brain anatomy for the first time.
- The research reveals variations in brain structure across species, including new findings about the sulcal patterns in Theropithecus oswaldi and similarities in neuroanatomy between Cercopithecoides williamsi and other primates, highlighting the need for further investigation into primate brain evolution.
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- * Researchers found canonical neurogenic zones, distinct labeling of new neurons in the hippocampus, and identified a rostral migratory stream that leads to the olfactory bulb, showcasing a significant terminal field of immature neurons.
- * Unique findings, such as a high density of immature neurons between the rostral migratory stream and the piriform cortex, suggest similarities between microchiropterans and insectivores, contributing to their evolutionary understanding.
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- Researchers studied the retinal ganglion cell distribution and spatial resolution in eight species of African megabats, focusing on their roosting and feeding behaviors in different microhabitats.
- They discovered that megabats roosting in open areas have a higher density of retinal ganglion cells, leading to better visual resolution, while those in enclosed spaces exhibit lower density and resolution.
- The findings suggest that the variations in retinal organization relate to the bats' ecological needs for detecting food and navigating their specific environments.
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- The potto is a slow-moving primate found in African rainforests, adapted for foraging and evading predators in the tree canopy.
- Researchers studied the potto's retina, measuring retinal ganglion cells and their distribution, finding about 210,000 cells, with a unique organization that aids in contrast sensitivity and motion detection.
- The study revealed an absence of a fovea, but the structure and density of the potto's retina may still help it forage for small invertebrates and detect predators effectively while relying primarily on its sense of smell.
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- The study examines the organization of cholinergic, catecholaminergic, serotonergic, and orexinergic neurons in five insectivore species and compares them to other mammals.
- Findings show that while most neural structures are similar across species, specific differences may indicate evolutionary relationships, particularly between shrews and microchiropterans (a group of bats).
- Notable differences include the absence of certain nuclei in shrew species, which aligns them more closely with microchiropterans, suggesting a potential phylogenetic link.