Biology subjects

Karl, S.

Publications and source records attributed to Karl, S..

10 recordsLinked to original sources

bioRxiv2025

Compromised futures: gastrointestinal parasites reduce survival and recruitment but not reproductive performance in wild female spotted hyenas (Crocuta crocuta)

BackgroundGastrointestinal parasitic (GIP) infections can decrease the survival and reproductive performance of humans and livestock. Even so, the immediate and delayed fitness consequences of GIP in unmanaged wild mammal populations, particularly during the sensitive and energetically demanding early life stage, remain largely unknown. MethodsWe investigate non-invasively the effects of GIP during early life on the survival to adulthood, age at first reproduction and longevity of 68 individually known female spotted hyenas in the Serengeti National Park, Tanzania. We also test whether a high investment in gastrointestinal local immunity (i.e. faecal mucin and immunoglobulin A) and an elevated allostatic load (i.e. faecal glucocorticoid metabolites) decrease these measures of performance, when controlling for resource availability and maternal effects (i.e. maternal social rank) using logistic regression and Cox proportional hazards models. ResultsAncylostoma sp. infections and the level of immunoglobulin A both negatively associate with survival to adulthood, probably because of the damage caused by the parasite and resource allocation trade-off between immunity and maintenance. Conversely, maternal social rank has a positive influence on survival to adulthood and longevity. Immune responses, allostatic load and GIP do not affect the age at first reproduction, suggesting either no effect, a complex interaction between different life stages, or a more immediate time-dependent effect. ConclusionOur study highlights the critical role of GIP infections and maternal effects on early-life fitness and long-term outcomes in females of a wild carnivore, thereby contributing to our understanding of ecological dynamics in unmanaged ecosystems.

ecology↗

bioRxiv2024

Spotted hyena gut cross-talks:Symbionts modulate mucosal immunity

The intestinal mucosa is at the front line of host-microbiome interactions, but little is known about these interactions within natural populations. Here, we non-invasively investigated associations between the gut microbiome and mucosal immune measures while controlling for host, social, and ecological factors in 199 samples of 158 wild spotted hyenas (Crocuta crocuta) in the Serengeti National Park, Tanzania. We profiled the microbiome composition, including bacteria, fungi and parasites, using a multi-amplicon approach, and measured faecal immunoglobulin A and mucin. Probabilistic models indicated that both immune measures predict microbiome similarity among individuals in an age-dependent manner. The strength of the association effect varied, being strongest within bacteria, intermediate within parasites, and weakest within fungi communities. Machine learning regression accurately predicted both measures and identified the taxa driving these associations: symbiotic bacteria reported in humans and laboratory mice, unclassified bacteria, a hookworm, host DNA likely reflecting inflammation, and diet. Our findings indicate a complex interplay between the host, its environment and symbionts. These findings increase our knowledge of the gut microbiome in natural populations, which harbour highly dynamic and diverse eukaryotes under the influence of unpredictable environmental factors and where selection is not artificially biased.

ecology↗

bioRxiv2024

Global, asynchronous partial sweeps at multiple insecticide resistance genes in Aedes mosquitoes

Aedes aegypti (yellow fever mosquito) and Ae. albopictus (Asian tiger mosquito) are globally invasive pests that confer the worlds dengue burden. Insecticide-based man-agement has led to the evolution of insecticide resistance in both species, though the genetic architecture and geographical spread of resistance remains incompletely un-derstood. This study investigates partial selective sweeps at resistance genes on two chromosomes and characterises their spread across populations. Sweeps at the volt-age-sensitive sodium channel gene (VSSC) on chromosome 3 correspond to one nu-cleotide substitution in Ae. albopictus and three substitutions in Ae. aegypti, including two at the same nucleotide position (F1534C) that have evolved and spread independently. In Ae. aegypti, we also identified partial sweeps at a second locus on chromosome 2. This locus contained 15 glutathione S-transferase (GST) epsilon class genes with significant copy number variation among populations and where three distinct genetic backgrounds have spread across the Indo-Pacific region, the Americas, and Australia. Local geographical patterns and linkage networks indicate VSSC and GST backgrounds probably spread at different times and interact locally with different genes to produce resistance phenotypes. These findings highlight the rapid spread of resistance genes globally and are evidence for the critical importance of GST genes in resistance evolution.

evolutionary biology↗

bioRxiv2023

Functional mapping of the somatosensory cortex using noninvasive fMRI and touch in awake dogs

Dogs are increasingly used as a model for neuroscience due to their ability to undergo functional MRI fully awake and unrestrained, after extensive behavioral training. Still, we know rather little about dogs basic functional neuroanatomy, including how basic perceptual and motor functions are localized in their brains. This is a major shortcoming in interpreting activations obtained in dog fMRI. The aim of this preregistered study was to localize areas associated with somatosensory processing. To this end, we touched N = 22 dogs undergoing fMRI scanning on their left and right flanks using a wooden rod. We identified activation in anatomically defined primary and secondary somatosensory areas (SI and SII), lateralized to the contralateral hemisphere depending on the side of touch, as well as activations, beyond an anatomical mask of SI and SII, in the cingulate cortex, right cerebellum and vermis, and the Sylvian gyri. These activations may partly relate to motor control (cerebellum, cingulate), but also potentially to higher-order cognitive processing of somatosensory stimuli (rostral Sylvian gyri), and the affective aspects of the stimulation (cingulate). We also found evidence for individual side biases in a vast majority of dogs in our sample, pointing at functional lateralization of somatosensory processing. These findings not only provide further evidence that fMRI is suited to localize neuro-cognitive processing in dogs in vivo, but also expand our understanding of touch processing in mammals, beyond classically defined primary and secondary somatosensory cortices. Significance StatementTo understand brain function and evolution, it is necessary to look beyond the human lineage. This study provides insights into the engagement of brain areas related to somatosensation using whole-brain non-invasive neuroimaging of trained, non-sedated, and unrestrained pet dogs. It showcases again the usefulness of non-invasive methods, in particular fMRI, for investigating brain function and advances the mapping of brain functions in dogs; using this non-invasive approach without sedation, we are able to identify previously unknown potential higher-order processing areas and offer a quantification of touch processing lateralization.

neuroscience↗

bioRxiv2023

Action observation reveals a network with divergent temporal and parietal lobe engagement in dogs compared to humans

Action observation is a fundamental pillar of social cognition. Neuroimaging research has revealed a human and primate action observation network (AON) encompassing fronto-temporo-parietal areas with links to a species imitation tendencies and relative lobe expansion. Dogs (Canis familiaris) have good action perception and imitation skills and a less expanded parietal than temporal lobe, but their AON remains unexplored. We conducted a functional MRI study with 28 dogs and 40 humans and found functionally analogous involvement of somatosensory and temporal brain areas of both species AONs and responses to transitive and intransitive action observation in line with their imitative skills. However, activation and task-based functional connectivity measures suggested significantly less parietal lobe involvement in dogs than in humans. These findings advance our understanding of the neural bases of action understanding and the convergent evolution of social cognition, with analogies and differences resulting from similar social environments and divergent brain expansion, respectively.

neuroscience↗

bioRxiv2022

Validation of a new coil array tailored for dog functional magnetic resonance imaging (fMRI) studies

Comparative neuroimaging allows for the identification of similarities and differences between species. It provides an important and promising avenue, to answer questions about the evolutionary origins of the brains organization, in terms of both structure and function. Dog fMRI has recently become one particularly promising and increasingly used approach to study brain function and coevolution. In dog neuroimaging, image acquisition has so far been mostly performed with coils originally developed for use in human MRI. Since such coils have been tailored to human anatomy, their sensitivity and data quality is likely not optimal for dog MRI. Therefore, we developed a multi-channel receive coil (K9 coil) tailored for high-resolution functional imaging in canines, optimized for dog cranial anatomy. In this paper we report structural (n = 9) as well as functional imaging data (resting-state, n = 6; simple visual paradigm, n = 9) collected with the K9 coil in comparison to reference data collected with a human knee coil. Our results show that the K9 coil significantly outperforms the human knee coil, improving the signal-to-noise ratio across the imaging modalities. We noted increases of roughly 45% signal-to-noise in the structural and functional domain. In terms of translation to functional fMRI data collected in a visual flickering checkerboard paradigm, group-level analyses show that the K9 coil performs better than the knee coil as well. These findings demonstrate how hardware improvements may be instrumental in driving data quality, and thus, quality of imaging results, for dog-human comparative neuroimaging. Significance StatementComparative neuroimaging is a powerful avenue to discover evolutionary mechanisms at the brain level. However, data quality is a major constraint in non-human functional magnetic resonance imaging. We describe a novel canine head coil for magnetic resonance imaging, designed specifically for dog cranial anatomy. Data quality performance and improvements over previously used human knee coils are described quantitatively. In brief, the canine coil improved signal quality substantially across both structural and functional imaging domains, with strongest improvements noted on the cortical surface.

neuroscience↗

bioRxiv2021

Similarities and differences of face and body perception in the dog (Canis familiaris) and human brain

Comparing the neural correlates of socio-cognitive skills across species provides insights into the evolution of the social brain and has revealed face- and body-sensitive regions in the primate temporal lobe. Although from a different lineage, dogs share convergent visuo-cognitive skills with humans and a temporal lobe which evolved independently in carnivores. We investigated the neural correlates of face and body perception in dogs (N = 15) and humans (N = 40) using functional MRI. Combining univariate and multivariate analysis approaches, we found functionally analogous occipito-temporal regions involved in the perception of animate entities and bodies in both species, while only humans had regions specialized for face perception. Though unpredicted, we also observed neural representations of faces compared to inanimate objects, and dog compared to human bodies in dog olfactory regions. These findings shed light on the evolutionary foundations of human and dog social cognition and the predominant role of the temporal lobe.

neuroscience↗

bioRxiv2020

Spatial population genomics of a recent mosquito invasion

Population genomic approaches can characterise dispersal across a single generation through to many generations in the past, bridging the gap between individual movement and intergenerational gene flow. These approaches are particularly useful when investigating dispersal in recently altered systems, where they provide a way of inferring long-distance dispersal between newly established populations and their interactions with existing populations. Human-mediated biological invasions represent such altered systems which can be investigated with appropriate study designs and analyses. Here we apply temporally-restricted sampling and a range of population genomic approaches to investigate dispersal in a 2004 invasion of Aedes albopictus (the Asian tiger mosquito) in the Torres Strait Islands (TSI) of Australia. We sampled mosquitoes from 13 TSI villages simultaneously and genotyped 373 mosquitoes at genome-wide single nucleotide polymorphisms (SNPs): 331 from the TSI, 36 from Papua New Guinea (PNG), and 4 incursive mosquitoes detected in uninvaded regions. Within villages, spatial genetic structure varied substantially but overall displayed isolation by distance and a neighbourhood size of 232-577. Close kin dyads revealed recent movement between islands 31-203 km apart, and deep learning inferences showed incursive Ae. albopictus had travelled to uninvaded regions from both adjacent and non-adjacent islands. Private alleles and a coancestry matrix indicated direct gene flow from PNG into nearby islands. Outlier analyses also detected four linked alleles introgressed from PNG, with the alleles surrounding 12 resistance-associated cytochrome P450 genes. By treating dispersal as both an intergenerational process and a set of discrete events, we describe a highly interconnected invasive system.

genomics↗

bioRxiv2020

Tailored haemodynamic response function increases detection power of fMRI in awake dogs (Canis familiaris)

Functional magnetic resonance imaging (fMRI) of awake and unrestrained dogs (Canis familiaris) has been established as a novel opportunity for comparative neuroimaging, promising important insights into the evolutionary roots of human brain function and cognition. However, data processing and analysis pipelines are often derivatives of methodological standards developed for human neuroimaging, which may be problematic due to profound neurophysiological and anatomical differences between humans and dogs. Here, we explore whether dog fMRI studies would benefit from a tailored dog haemodynamic response function (HRF). In two independent experiments, dogs were presented with different visual stimuli. BOLD signal changes in the visual cortex during these experiments were used for (a) the identification and estimation of a tailored dog HRF, and (b) the independent validation of the resulting dog HRF estimate. Time course analyses revealed that the BOLD signal in the primary visual cortex peaks significantly earlier in dogs compared to humans, while being comparable in shape. Deriving a tailored dog HRF significantly improved the model fit in both experiments, compared to the canonical HRF used in human fMRI. Using the dog HRF yielded significantly increased activation during visual stimulation, extending from the occipital lobe, to the caudal parietal cortex, the bilateral temporal cortex, and into bilateral hippocampal and thalamic regions. In sum, our findings provide robust evidence for an earlier onset of the dog HRF in a visual stimulation paradigm, and suggest that using such an HRF will be important to increase fMRI detection power in canine neuroimaging. By providing the parameters of the tailored dog HRF and related code, we encourage and enable other researchers to validate whether our findings generalize to other sensory modalities and experimental paradigms. HighlightsO_LIDog fMRI typically uses human HRF, but underlying neurophysiology might differ C_LIO_LIV1 BOLD signal peaked earlier in dogs than predicted by the human HRF C_LIO_LITailored dog HRF improved model fit when tested with independent data C_LIO_LIWhole-brain comparisons confirmed increased detection power for tailored dog HRF C_LIO_LIDog fMRI will benefit from increased detection power of tailored HRF C_LI

neuroscience↗

bioRxiv2017

Long-term sustained malaria control leads to inbreeding and fragmentation of Plasmodium vivax populations

The human malaria parasite Plasmodium vivax is resistant to malaria control strategies maintaining high genetic diversity even when transmission is low. To investigate whether declining P. vivax transmission leads to increasing P. vivax population structure that would facilitate elimination, we genotyped samples from a wide range of transmission intensities and spatial scales in the Southwest Pacific, including two time points at one site (Tetere, Solomon Islands) during intensified control. Analysis of 887 P. vivax microsatellite haplotypes from hyperendemic Papua New Guinea (PNG, n = 443), meso-hyperendemic Solomon Islands (n= 420), and hypoendemic Vanuatu (n=24) revealed increasing population structure and multilocus linkage disequilibrium and a modest decline in diversity as transmission decreases over space and time. In Solomon Islands, which has had sustained control efforts for 20 years, and Vanuatu, which has experienced sustained low transmission for many years, significant population structure was observed at different spatial scales. We conclude that control efforts will eventually impact P. vivax population structure and with sustained pressure, populations may eventually fragment into a limited number of clustered foci that could be targeted for elimination.

epidemiology↗