Biology subjects

Viblanc, V. A.

Publications and source records attributed to Viblanc, V. A..

3 recordsLinked to original sources

bioRxiv2023

Surface temperatures are influenced by handling stress independently of glucocorticoid levels in wild king penguins

Assessing the physiological stress responses of wild animals opens a window for understanding how organisms cope with environmental challenges. Since stress response is associated with changes in body temperature, the use of body surface temperature through thermal imaging could help to measure acute and chronic stress responses non-invasively. We used thermal imaging, acute handling-stress protocol and an experimental manipulation of corticosterone (the main glucocorticoid hormone in birds) levels in breeding king penguins (Aptenodytes patagonicus), to assess: 1. the potential contribution of the Hypothalamo-Pituitary-Adrenal (HPA) axis in mediating chronic and acute stress-induced changes in adult surface temperature, 2. the influence of HPA axis manipulation on parental investment through thermal imaging of eggs and brooded chicks, and 3. the impact of parental treatment on offspring thermals response to acute handling. Maximum eye temperature (Teye) increased and minimum beak temperature (Tbeak) decreased in response to handling stress in adults, but neither basal nor stress-induced surface temperatures were significantly affected by corticosterone implant. While egg temperature was not significantly influenced by parental treatment, we found a surprising pattern for chicks: chicks brooded by the (non-implanted) partner of corticosterone-implanted individuals exhibited higher surface temperature (both Teye and Tbeak) than those brooded by glucocorticoid-implanted or control parents. Chicks response to handling in terms of surface temperature was characterized by a drop in both Teye and Tbeak independently of parental treatment. We conclude that the HPA axis seems unlikely to play a major role in determining chronic or acute changes in surface temperature in king penguins. Changes in surface temperature may primarily be mediated by the Sympathetic-Adrenal-Medullary (SAM) axis in response to stressful situations. Our experiment did not reveal a direct impact of parental HPA axis manipulation on parental investment (egg or chick temperature), but a potential influence on the partners brooding behaviour. HighlightsO_LIExperimental increase in corticosterone does not affect king penguins surface temperature C_LIO_LIAcute handling stress increases eye but decreases beak surface temperature in adults C_LIO_LIAcute handling decreases both eye and beak surface temperatures in young chicks C_LIO_LIParental corticosterone treatment does not affect egg surface temperature during incubation C_LIO_LIChicks brooded by non-implanted partners of corticosterone parents are warmer than chicks brooded by others adults. C_LI

zoology↗

bioRxiv2023

Early-life environmental effects on mitochondrial aerobic metabolism: an experimental brood size manipulation in wild great tits

Parental care (including postnatal provisioning) is a major component of the offsprings early-life environment. In avian species, the number of chicks in the nest and subsequent sibling competition for food are known to affect chicks growth, leading in some cases to long-lasting effects for the offspring. Because of its central role in converting energy, variation in the offsprings mitochondrial metabolism could be an important pathway underlying variation in growth patterns. Here, we performed a brood size manipulation in great tits (Parus major) to unravel its impact on offsprings mitochondrial metabolism and reactive oxygen species (ROS) production in red blood cells. We investigated the effects of brood size on chicks growth and survival, and tested for long-lasting effects on juvenile mitochondrial metabolism and phenotype. As expected, chicks raised in reduced broods had a higher body mass compared to enlarged and control groups. However, mitochondrial metabolism and ROS production were not significantly affected by the treatment either at chick or juvenile stages. Chicks in very small broods were smaller in size and had higher mitochondrial metabolic rates. The nest of rearing has a significant effect on nestling mitochondrial metabolism, yet variation in mitochondrial metabolism at the early-life stages are not associated with survival chances. The contribution of the rearing environment in determining offspring mitochondrial metabolism emphasizes the plasticity of mitochondrial metabolism in changing environments. Further studies would be needed to closely investigate what are the major environmental cues affecting the offspring mitochondrial metabolism during the growth period.

physiology↗

bioRxiv2021

Reliable hypotheses testing in animal social network analyses: global index, index of interactions and residual regression

Animal social network analyses (ASNA) have led to a foundational shift in our understanding of animal sociality that transcends the disciplinary boundaries of genetics, spatial movements, epidemiology, information transmission, evolution, species assemblages and conservation. However, some analytical protocols (i.e., permutation tests) used in ASNA have recently been called into question due to the unacceptable rates of false negatives (type I error) and false positives (type II error) they generate in statistical hypothesis testing. Here, we show that these rates are related to the way in which observation heterogeneity is accounted for in association indices. To solve this issue, we propose a method termed the "global index" (GI) that consists of computing the average of individual associations indices per unit of time. In addition, we developed an "index of interactions" (II) that allows the use of the GI approach for directed behaviours. Our simulations show that GI: 1) returns more reasonable rates of false negatives and positives, with or without observational biases in the collected data, 2) can be applied to both directed and undirected behaviours, 3) can be applied to focal sampling, scan sampling or "gambit of the group" data collection protocols, and 4) can be applied to first- and second-order social network measures. Finally, we provide a method to control for non-social biological confounding factors using linear regression residuals. By providing a reliable approach for a wide range of scenarios, we propose a novel methodology in ASNA with the aim of better understanding social interactions from a mechanistic, ecological and evolutionary perspective.

animal behavior and cognition↗