Biology subjects

Maraci, O.

Publications and source records attributed to Maraci, O..

5 recordsLinked to original sources

bioRxiv2025

Gut microbiome variation in juvenile blue tits in a European urban mosaic.

Urbanisation transforms natural environments, impacting not only wild animals living in cities but also the microorganisms they are hosting. To better understand urban-driven variation in microbiological composition and diversity in the gut of birds developing in urban areas, we collected faecal samples from blue tit Cyanistes caeruleus nestlings using nestboxes distributed across the capital city of Warsaw, Poland. Sampling included a variety of urban habitats, a suburban village and a natural forest area. Microbiome analysis unveiled a pattern of reduced alpha and beta diversity in urbanised settings driven by impervious surfaces. Additionally, we observed that this effect was year-dependent, therefore highlighting the importance of temporal replication in ecological research. Furthermore, comparing two cavity types (natural and human-made), we demonstrated that artificial nestboxes, a tool widely used in field ecology, can impact the microbiome assembly in nestlings. Our results align with and expand upon earlier insights in great tit Parus major gut microbiome variation inferred in the same urban study system on a species ecologically related to the blue tit, confirming the pervasive impact of urbanisation on the avian gut microbiome.

ecology↗

bioRxiv2025

Skin but not gut microbial communities in Antarctic fur seals vary with social density

Comparative studies of microbial communities occupying different body sites in wild vertebrates are scarce, but they are crucial for advancing our understanding of the ecological and evolutionary factors shaping animal microbiomes. We therefore used a "natural experiment" comprising mother-offspring pairs from two adjacent Antarctic fur seal breeding colonies that differ in social density to investigate differences between skin and gut microbial communities in relation to host-specific and environmental factors. Using 16S rRNA amplicon sequencing, we uncovered a strong influence of colony on the diversity and composition of skin but not gut microbial communities. Specifically, we observed a suppressive effect of high social density on skin microbial alpha diversity as well as an overabundance of phyla associated with diseases and bite wounds in the high-density colony. Our findings suggest that skin microbial communities may be more sensitive to external factors, whereas gut communities are more tightly regulated by the host. Overall, this study highlights the importance of considering multiple body sites and their distinct microbial communities to develop a more comprehensive understanding of the factors shaping microbial diversity and composition in marine mammals.

microbiology↗

bioRxiv2025

Lizards in energy-saving mode: Urban individuals are smaller and have lower metabolic rates

Human-induced rapid environmental change is intensifying globally. Urbanization, a major form of human-induced rapid environmental change, alters ecosystems and exposes wildlife to urban stressors, including altered ambient temperatures and resource shifts. These alterations can impose selective pressures on wildlife, influencing behavior, physiology, and morphology. Alterations in resource availability and quality, and ambient temperature may be especially important for ectotherms, which depend on environmental conditions for regulating body temperature and activity. To date, little research has examined the physiological changes of ectotherms that are associated with urban life. In this study, we measured standard metabolic rate (SMR; N = 38) and recorded body mass and size in common wall lizards (Podarcis muralis) from an urban (N = 123) and a semi-natural habitat (N = 125) in Croatia. Our results show that urban lizards exhibit a lower SMR, reduced body mass, and shorter snout-vent length than their semi-natural counterparts. Despite these differences, body condition, assessed via the scaled mass index, did not vary between the two habitat types, potentially reflecting adaptive responses to urbanization-related environmental pressures. These findings suggest adaptive strategies of reptiles in urban environments and highlight the importance of studying both physiological and morphological traits to better understand the effects of urbanization on wildlife.

zoology↗

bioRxiv2024

The gut microbiota-immune-brain axis in a wild vertebrate: dynamic interactions and health impacts

The gut microbiota-immune-brain axis is a feedback network which influences diverse physiological processes and plays a pivotal role in overall health and well-being. Although research in humans and laboratory mice has shed light into the associations and mechanisms governing this communication network, evidence of such interactions in wild, especially in young animals, is lacking. We therefore investigated these interactions during early development in a population of common buzzards (Buteo buteo) and their effects on individual condition. In a longitudinal study, we used a multi-marker approach to establish potential links between the bacterial and eukaryotic gut microbiota, a panel of immune assays and feather corticosterone measurements as a proxy for long-term stress. Using Bayesian structural equation modelling, we found no support for feedback between gut microbial diversity and immune or stress parameters. However, we did find strong relationships in the feedback network. Immunity was negatively correlated with corticosterone levels, and microbial diversity was positively associated with nestling body condition. Furthermore, corticosterone levels and eukaryotic microbiota diversity decreased with age while immune activity increased. The absence of conclusive support for the microbiota-immune-brain axis in common buzzard nestlings, coupled with the evidence for stress mediated immunosuppression, suggests a dominating role of stress-dominated maturation of the immune system during early development. Confounding factors inherent to wild systems and developing animals might override associations known from adult laboratory model subjects. The positive association between microbial diversity and body condition indicates the potential health benefits of possessing a diverse and stable microbiota.

microbiology↗

bioRxiv2021

Alterations to the Gut Microbiota of a Wild Juvenile Passerine in an Urban Mosaic

Urbanisation is a major anthropogenic perturbation that progressively alters multiple environmental parameters, thereby presenting novel evolutionary challenges to wild populations. Symbiotic microorganisms residing in the gastrointestinal tracts (gut) of vertebrates have well-established mutual connections with the physiology of their hosts and respond quickly to environmental alterations. However, the impacts of anthropogenic changes and urbanisation on gut microbiota remain poorly understood, especially in early development. To address this knowledge gap, we investigated the gut microbiota in juvenile great tits (Parus major) in an urban mosaic. First, we compared the microbiota of nestlings reared in artificial nest boxes or natural cavities. Next, we analysed microbiota variations employing two distinct urbanisation frameworks, (i) the classical urban/rural dichotomy and (ii) gradual changes in the amount of impervious surface area (ISA) in the urban space and identified the environmental variables that predicted the changes in the microbial communities. Alpha diversity was influenced by cavity type and by the amount of impervious surface surrounding the breeding location. Alpha diversity was also positively correlated with the tree cover density. Beta diversity differed between urban and rural sites, and these alterations covaried with sound pollution, the distance to the city centre and the distance to the closest road. Overall, the microbial communities reflect and are possibly influenced by the heterogeneous environmental modifications that are typical of the urban space. Strikingly, the choice of framework used to define the urban space can influence the outcomes of studies investigating animal-microbe symbiosis. Our results open new perspectives from which the potential function of microbial symbionts in the adaptation of their hosts to anthropogenic stress can be investigated.

ecology↗