Biology subjects

Tschirren, B.

Publications and source records attributed to Tschirren, B..

7 recordsLinked to original sources

bioRxiv2025

Proteomic characterisation of Japanese quails unique seminal foam

Male Japanese quail (Coturnix japonica) produce a unique proctodeal foam upon ejaculation which is thought to enhance fertilisation success. However, the precise function and proteomic characterisation of this foam remain largely unexplored. Using high throughput LC-MS/MS proteomics analysis, we characterised the proteome of the quail seminal foam for the first time. Our analysis confidently identified 224 proteins in the foam using 32 pooled samples from 96 males. 96.4% of proteins had orthologs in the closely related (diverged 35 million years ago) chicken (Gallus gallus) which generated 40 Gene Ontology terms. Further interrogation revealed proteins involved in sperm motility, maturation and DNA protection, suggesting the foam plays a role in fertilisation success. Proteins linked to immune defence and inflammation modulation were identified, indicating the foam may protect sperm from antigens and reduce female immunogenic responses. This work advances our understanding of the function and evolution of Japanese quail unique seminal foam and directs future experiments to investigate the role of key seminal foam proteins in post-copulatory sexual selection. Significance of the StudySeminal fluid plays an important role in fertilisation success, yet the molecular components of seminal fluid and their function remain poorly understood in most species. This study provides the first comprehensive proteomic characterisation of a unique seminal foam produced by the Japanese quail (Coturnix japonica), revealing its potential mechanistic function in sperm regulation, sperm motility, immune protection, and fertilisation success. By identifying key proteins associated with energy production, membrane fluidity, and sperm maturation, our findings suggest the foam may influence post-ejaculatory sperm function. Additionally, the identification of immunity proteins indicates a role in sperm protection and modulation of female immune responses. This study advances our understanding of avian reproductive biology and opens new avenues for investigating the specific role of seminal foam proteins in fertilisation dynamics and post-copulatory sexual selection.

evolutionary biology↗

bioRxiv2023

Rapid decline of prenatal maternal effects with age is independent of postnatal environment in a precocial bird

Maternal effects are an important source of phenotypic variation with potentially large fitness consequences, but how their importance varies with the quality of the environment across an individuals ontogeny is poorly understood. We bred Japanese quail (Coturnix japonica) of known pedigree and experimentally manipulated the quality of offspring diet, to estimate the importance of prenatal maternal effects in shaping variation in body mass from hatching to adulthood. Maternal genetic effects on body mass at hatching were strong, and largely caused by variation in egg mass, but their importance rapidly declined with age. Whereas there was a large effect of diet on growth, this did not affect the decline of maternal effects variance. The importance of additive genetic and residual variance increased with age, with the latter being considerably larger in the poor diet treatment. Hence, we found no evidence for prenatal maternal effect by postnatal environment interactions, and that prenatal maternal effects are rapidly replaced by direct additive genetic and residual effects when offspring start to develop outside the egg. Thereby these results shed new light on the dynamics of the role of maternal versus offspring genes across ontogeny and environments.

evolutionary biology↗

bioRxiv2021

Elevational changes in bacterial microbiota structure and diversity in an arthropod-disease vector

Environmental conditions change rapidly along elevational gradients and have been found to affect community composition in macroscopic taxa, with lower diversity typically observed at higher elevations. In contrast, microbial community responses to elevation are still poorly understood. Specifically, the effects of elevation on vector-associated microbiota have not been studied to date, even though the within-vector microbial community is known to influence vector competence for a range of zoonotic pathogens. Here we characterize the structure and diversity of the bacterial microbiota in an important zoonotic disease vector, the sheep tick Ixodes ricinus, along replicated elevational gradient (630 - 1673 masl) in the Swiss Alps. 16S rRNA sequencing of the whole within-tick bacterial microbiota of questing nymphs and adults revealed a decrease in Faiths phylogenetic microbial alpha diversity with increasing elevation, while beta diversity analyses revealed a lower variation in microbial community composition at higher elevations. We also found a higher microbial diversity later in the season and significant differences in microbial diversity among tick life stages and sexes, with lowest microbial alpha diversity observed in adult females. No associations between tick genetic diversity and bacterial diversity were observed. Our study demonstrates systematic changes in tick bacterial microbiota diversity along elevational gradients. The observed patterns mirror diversity changes along elevational gradients typically observed in macroscopic taxa, and they highlight the key role of environmental factors in shaping within-host microbial communities in ectotherms.

ecology↗

bioRxiv2019

Inter-specific variation of maternal thyroid hormones associate with migration, mode of development, and captivity: a phylogenetic comparative analysis

Life-history traits vary largely across species and several physiological parameters have been proposed to be associated with life-history variation, such as metabolic rates, glucocorticoids, and oxidative stress. Interestingly, the association between thyroid hormones (THs) and life history variation has never been considered, despite a close interaction between THs and these physiological traits. Because of the crucial effects on embryonic development, THs can also induce transgenerational plasticity when transferred to developing offspring, for instance, via egg yolks in birds. In this study, we compiled a unique data set of maternal yolk THs in 34 bird species across 17 families and 6 orders, and tested for associations with various life-history traits. Our phylogenetic mixed models indicated that both concentrations and total amounts of the two most important forms of THs (T3 and T4) were higher in the eggs of migratory species than in those of resident species, and that there were higher total amounts of T3 in the eggs of precocial species than in those of altricial species. However, maternal THs did not show clear associations with any traits of the pace-of-life syndrome, such as developmental duration, growth rate, or lifespan. When taking environmental factors into account, we found that captive species deposited higher TH concentrations and larger amounts in the egg yolks than wild species. These findings suggest that maternal THs are likely involved in the evolution of life-history variation, or vice versa.

evolutionary biology↗

bioRxiv2019

The great tit HapMap project: a continental-scale analysis of genomic variation in a songbird

A major aim of evolutionary biology is to understand why patterns of genomic diversity vary among populations and species. Large-scale genomic studies of widespread species are useful for studying how the environment and demographic history shape patterns of genomic divergence, and with the continually decreasing cost of sequencing and genotyping, such studies are now becoming feasible. Here, we carry out one of the most geographically comprehensive surveys of genomic variation in a wild vertebrate to date; the great tit (Parus major) HapMap project. We screened ca 500,000 SNP markers across 647 individuals from 29 populations, spanning almost the entire geographic range of the European great tit subspecies. We found that genome-wide variation was consistent with a recent colonisation across Europe from a single refugium in South-East Europe, with bottlenecks and reduced genetic diversity in island populations. Differentiation across the genome was highly heterogeneous, with clear "islands of differentiation" even among populations with very low levels of genome-wide differentiation. Low local recombination rate in the genome was a strong predictor of high local genomic differentiation (FST), especially in island and peripheral mainland populations, suggesting that the interplay between genetic drift and recombination is a key driver of highly heterogeneous differentiation landscapes. We also detected genomic outlier regions that were confined to one or more peripheral great tit populations, most likely as a result of recent directional selection at the range edges of this species. Haplotype-based measures of selection were also related to recombination rate, albeit less strongly, and highlighted population-specific sweeps that likely resulted from positive selection. These regions under positive selection contained candidate genes associated with morphology, thermal adaptation and colouration, providing promising avenues for future investigation. Our study highlights how comprehensive screens of genomic variation in wild organisms can provide unique insights into evolution.

evolutionary biology↗

bioRxiv2019

Human pathogen co-occurrence in Ixodes ricinus ticks: effects of landscape topography, climatic factors and microbiota interactions

The factors shaping microbial communities within organisms are still poorly understood. Besides ecological factors and host characteristics, direct interactions among microbes may shape the occurrence of microbes and the structure of communities. In the past it has been difficult to disentangle if patterns of microbial co-occurrence are due to facilitation or competition effects, or shaped by shared ecological preferences (i.e., environmental filtering). Here we use a joint species distribution model to characterize the bacterial microbiota composition of an important human disease vector, the sheep tick Ixodes ricinus, along ecological gradients in the Swiss Alps, and to test for facilitation or competition effects among human pathogens and tick endosymbionts. We identify a number of ecological variables that significantly predicted the diversity of tick microbial community and the occurrence of specific tick endosymbionts and human pathogens. However, ecological associations were generally microbe-specific rather than universal. We also found evidence for significant microbe interactions, in particular widespread facilitation among pathogens, which promotes pathogen co-infection within ticks, as well as competition between the tick endosymbiont Spiroplasma and a number of human pathogens. These findings highlight that direct interactions among microbes can affect the vector competence of ticks and thereby tick-borne disease dynamics.

ecology↗

bioRxiv2018

Does Borrelia burgdorferi sensu lato facilitate the colonisation of marginal habitats by Ixodes ricinus? A correlative study in the Swiss Alps

Parasites can alter host and vector phenotype and thereby affect ecological processes in natural populations. Laboratory studies have shown that Borrelia burgdorferi sensu lato, the causative agent of human Lyme borreliosis, induces physiological alterations in its main tick vector in Europe, Ixodes ricinus, which increase its survival under challenging conditions. We hypothesise that these phenotypic alterations may allow I. ricinus to colonise marginal habitats, thereby fuelling the ongoing range expansion of I. ricinus towards higher elevations and latitudes induced by climate change. To explore the potential for such an effect under natural conditions, we studied the prevalence of B. burgdorferi s.l. in questing I. ricinus and its variation with elevation in the Swiss Alps. We screened for B. burgdorferi s.l. infection in questing nymphs of I. ricinus (N = 411) from 15 sites between 528 and 1774 m.a.s.l to test if B. burgdorferi s.l. prevalence is higher at high elevations (i.e. in marginal habitats). We found that B. burgdorferi s.l. prevalence in I. ricinus nymphs decreased linearly with increasing elevation and that it was 12.6% lower in I. ricinus nymphs collected at high elevations compared to nymphs in the core range. Thus, we found no evidence that the B. burgdorferi s.l.-induced alterations of I. ricinus phenotype facilitate the colonisation of marginal habitats in the wild. These findings have implications for a better understanding of eco-evolutionary processes in natural host-parasite systems, as well as the assessment of Lyme borreliosis risk in regions where I. ricinus is newly emerging.

ecology↗