Biology subjects

Koren, L.

Publications and source records attributed to Koren, L..

9 recordsLinked to original sources

bioRxiv2026

Who takes the risk to forage? Testing consistent inter-individual behavioural variation in wild vervet monkeys (Chlorocebus pygerythrus)

Risk-taking behaviour permeates daily decision-making across many taxa and has significant impact on fitness outcomes. Previous research finds that individuals display consistent tendencies in their propensity to take risks, often labelled as a "Boldness-Shyness" personality trait. In this experimental study, we investigated repeatability in risk-taking behaviour in 241 wild vervet monkeys by measuring their responses to capture threat (via human-initiated darting procedure) and predation threat (via two predator models). We further examined the influence of socio-demographic, group identity and hormonal factors on risk-taking behaviour. We found that multiple behavioural responses, including the likelihood of approaching a food source under threat, were consistent across contexts. Risk-taking behaviour was influenced by age, sex, dominance rank, and hormonal profiles: juveniles, males, and higher-ranking individuals were more likely to approach food under (perceived) predation risk. Additionally, we observed significant among-group differences, suggesting that individuals within the same social group exhibit similar risk sensitivities, potentially due to social facilitation or shared environmental effects. The findings contribute to our understanding of animal personality and the ecological and social drivers underlying variation in risk-related behaviours.

animal behavior and cognition↗

bioRxiv2025

In vivo semen characterization and seasonal variation in Procavia capensis males

Seasonal reproduction is common among wild mammals, but male fertility traits are often understudied. The rock hyrax (Procavia capensis) is a seasonal breeder with a narrow reproductive window, yet its semen characteristics and seasonal variation remain poorly understood. Our objectives were to develop and validate an electroejaculation protocol for semen collection, and to enable, for the first time, in vivo assessments of sperm morphology, ultrastructure, morphometry, and seasonal variation in semen quality in both captive and wild populations. A total of 70 semen collection attempts were conducted: 17 in captive males at [~]monthly intervals over one year, and 53 in wild males just before peak mating season and again 2-4 weeks later, across three consecutive years (2021-2023). Electroejaculation was well tolerated and effective, particularly around the mating season, eliciting consistent responses and yielding sperm-containing ejaculates in 88.7% of wild procedures. Sperm morphometry revealed a mean total length of [~]56{micro}m, with ultrastructural features resembling other eutherian mammals. Seasonal analysis demonstrated significantly higher sperm concentration, motility, and normal morphology during peak mating season compared to later samples. Post-peak samples showed increased structural abnormalities, including midpiece and principal piece defects, and signs of disrupted spermatogenesis and epididymal maturation. Cytology and high-resolution scanning electron microscopy confirmed these findings, revealing compromised sperm integrity and elevated round cell counts outside the breeding peak. This study establishes the first in vivo semen collection protocol and comprehensive semen evaluation in the rock hyrax, revealing seasonal variation in male fertility and enabling repeatable, non-lethal reproductive monitoring.

physiology↗

bioRxiv2023

Living fast, dying young: anthropogenic habitat modification influences the fitness and life history traits of a cooperative breeder

Modification of natural habitats can lead to an ecological trap, as animals can maladaptively select lower-quality habitats over natural landscapes. Modified habitats reduce group size and prevalence, the success of dispersing individuals, and breeding success. However, little is known about how these effects on fitness affect the sociality of cooperative breeding species, which may be particularly susceptible to habitat modification. Here we show that the selection of anthropogenically modified habitats negatively affects the fitness, which has consequences in the life history traits of a cooperative breeder. We used data collected during six years from a monitored population of Arabian babblers (Argya squamiceps) and found that groups living in modified habitats breed more than those in natural habitats but that juvenile and adult survival in modified habitats was lower. Individuals living in modified habitats acquired dominance earlier than individuals from natural habitats. Males in modified habitats also dispersed earlier than those from natural habitats. Our results suggest that modified habitats entail an ecological trap for Arabian babblers, which adjusts their life history traits as a response. Understanding the adaptation of social and cooperative breeding species to habitat modification is the first step for mitigating the processes behind human-related population declines.

ecology↗

bioRxiv2023

Sex-specific relationship between maternal and neonate cortisol in a free-ranging large mammal

Maternal phenotypes can have long-term effects on offspring phenotypes. These maternal effects may begin during gestation, when maternal glucocorticoid (GC) levels may affect foetal GC levels, thereby having an organizational effect on the offspring phenotype. Recent studies have showed that maternal effects may be different between the sexes. However, how maternal GC levels relate to foetal levels is still not completely understood. Here we related, for the first time in a free-ranging large mammal, the fallow deer (Dama dama), maternal GC levels with foetal in utero GC levels. We did this in a non-invasive way by quantifying cortisol metabolites from faecal samples collected from pregnant does during late gestation, as proxy for maternal GC level. These were then related to GC levels from hair of their neonate offspring (n = 40). We have shown that maternal GC levels were positively associated with foetal GC levels, but only in female offspring. These findings highlight sex differences, which may have evolved to optimize male growth at the cost of survival.

ecology↗

bioRxiv2022

Quantitative genetic study suggests sex-specific genetic architecture for fetal testosterone in a wild mammal

Testosterone plays a critical role in mediating fitness-related traits in many species. Although it is highly responsive to environmental and social conditions, evidence from several species show a heritable component to its individual variation. Despite the known effects that in utero testosterone exposure have on adult fitness, the heritable component of individual testosterone variation in fetuses is mostly unexplored. Furthermore, testosterone has sex-differential effects on fetal development, i.e., a specific level may be beneficial for male fetuses but detrimental for females. The above mentioned may lead to a different genetic structure underlying the heritability of testosterone between the sexes. Here, we used a wild animal model, the feral nutria, quantified testosterone using hair-testing and estimated its heritability between parent and offspring from the same and opposite sex. We found that in utero accumulated hair testosterone levels were heritable between parents and offspring of the same sex. However, there was a low additive genetic covariance between the sexes, and a relatively low cross-sex genetic correlation, suggesting a potential for sex-dependent trait evolution, expressed early on, in utero.

molecular biology↗

bioRxiv2021

Experimental corticosterone manipulation increases mature feather corticosterone content: implications for inferring avian stress history from feather analyses

Feathers incorporate plasma corticosterone (CORT) during their development and, because feathers lack blood supply at maturity, the CORT content of feathers (CORTf) is presumed to represent an integrated average of plasma CORT levels during feather growth. We tested this assumption by quantifying CORTf in feathers of house sparrows (Passer domesticus) that were plucked before and after being implanted with either a corticosterone-filled, metyrapone-filled, or empty (sham) silastic capsule. Two of the seven flight feathers collected from each bird were fully grown when birds received implants. We found that CORTf of all seven feathers corresponded with treatment type, and with plasma CORT levels of non-moulting reference sparrows also given these implants. We also found that CORTf of the two mature feathers of each bird were 4 to 10-fold higher than values measured in new feathers. Given the avascular nature of mature feathers, and the fact that we did not wash the feathers prior to analysis, the most plausible explanation for our results is that CORT was externally deposited on feathers after implant. This outcome emphasises the need for follow-up studies to identify the external sources of CORT that may affect the CORTf of feathers. We hope this study will stimulate discussions and further much needed studies on the mechanism of CORT deposition in feathers and open exciting opportunities for application of such methods in ecological research, such as measuring multiple time scales in such a non-invasive manner.

physiology↗

bioRxiv2020

Chemotherapeutic Nanoparticles Accumulate in the Female Reproductive System during Ovulation Affecting Fertility and Anticancer Activity

Throughout the female menstrual cycle, physiological changes occur that affect the biodistribution of nanoparticles within the reproductive system. This can have positive or negative effects. We demonstrate a 2-fold increase in nanoparticle accumulation in the ovaries during female mouse ovulation compared to the non-ovulatory stage following intravenous administration. Accumulation in the reproductive system is favored by nanoparticles smaller than 100 nm. Chemotherapeutic nanoparticles administered during ovulation increased ovarian toxicity and decreased short-term and long-term fertility when compared to the free drug. Breast cancer treated with nanomedicines during ovulation results in higher drug accumulation in the reproductive system rather than at the site of the tumor, reducing treatment efficacy. Conversely, ovarian cancer treatment was improved by enhanced nanoparticle accumulation in the ovaries during ovulation. Our findings suggest that the menstrual cycle should be considered when designing and implementing nanotherapeutics for females.

bioengineering↗

bioRxiv2019

Attentional Networks during the Menstrual Cycle

The menstrual cycle is characterized partially by fluctuations of the ovarian hormones estradiol (E2) and progesterone (P4), which are implicated in the regulation of cognition. Research on attention in the different stages of the menstrual cycle is sparse, and the three attentional networks (alerting, orienting and executive) and their interaction were not explored during the menstrual cycle. In the current study, we used the ANT-I (attentional network test - interactions) to examine two groups of women: naturally cycling (NC) - those with a regular menstrual cycle, and oral contraceptives (OC) - those using OC and characterized with low and steady ovarian hormone levels. We tested their performance at two time points that fit, in natural cycles, the early follicular phase and the early luteal phase. We found no differences in performance between NC and OC in low ovarian hormone states (Both phases for the OC group and early follicular phase for the NC group). However, the NC group in the early luteal phase exhibited the same pattern of responses for alerting and no-alerting conditions, resulting in a better conflict resolution (executive) when attention is oriented to the target. Results-driven exploratory regression analysis of E2 and P4 suggested that change in P4 from early follicular to early luteal phases was a mediator for the alerting effect found. In conclusion, the alerting state found with or without alertness manipulation suggests that there is a progesterone mediated activation of the alerting system during the mid-luteal phase.

animal behavior and cognition↗

bioRxiv2018

Evolution of embryo implantation was enabled by the origin of decidual cells in eutherian mammals

Embryo implantation is the first step in the establishment of pregnancy in eutherian (Placental) mammals. Although viviparity evolved prior to the common ancestor of marsupials and eutherian mammals (therian ancestor), implantation is unique to eutherians. The ancestral therian pregnancy likely involved a short phase of attachment between the fetal and maternal tissues followed by parturition rather than implantation, similar to the mode of pregnancy found in marsupials such as the opossum. Embryo implantation in eutherian mammals as well as embryo attachment in opossum, induce a homologous inflammatory response in the uterus. Here, we elucidate the evolutionary mechanism by which the ancestral inflammatory fetal-maternal attachment was transformed into the process of implantation. We performed a comparative transcriptomic and immunohistochemical study of the gravid and non-gravid uteri of two eutherian mammals, armadillo (Dasypus novemcinctus) and hyrax (Procavia capensis); a marsupial outgroup, opossum (Monodelphis domestica); and compared it to previously published data on rabbit (Oryctolagus cuniculus). This taxon sampling allows inference of the eutherian ancestral state. Our results show that in the eutherian lineage, the ancestral inflammatory response was domesticated by suppressing a detrimental component viz. signaling by the cytokine IL17A, while retaining components that are beneficial to placentation, viz. angiogenesis, vascular permeability, remodeling of extracellular matrix. IL17A mediates recruitment of neutrophils to inflamed mucosal tissues, which, if unchecked, can damage the uterus as well as the embryo and lead to expulsion of the fetus. We hypothesized that the uterine decidual stromal cells, which evolved coincidentally with embryo implantation, evolved, in part, to prevent IL17A-mediated neutrophil infiltration. We tested a prediction of this hypothesis in vitro, and showed that decidual stromal cells can suppress differentiation of human naive T cells into IL17A-producing Th17 cells. Together, these results provide a mechanistic understanding of early stages of the evolution of the eutherian mode of pregnancy, and also identify a potentially ancestral function of an evolutionary novelty, the decidual stromal cell-type.

evolutionary biology↗