Biology subjects

Mastromonaco, G. F.

Publications and source records attributed to Mastromonaco, G. F..

5 recordsLinked to original sources

bioRxiv2024

Interactive effects of temperature acclimation and dietary fatty acids on metabolic rate and body composition of zebra finches (Taeniopygia guttata)

Climate change is contributing to geographic range shifts in many bird species, with possible exposure to novel diets. How individuals respond physiologically across chronic time frames to the interacting effects of diet and environmental temperature has been little explored. We acclimated zebra finches to either cool (20-24{degrees}C) or thermoneutral (35{degrees}C) temperatures over 6-months and provided them with diets enriched in either unsaturated or saturated fatty acids. We measured body mass throughout the study, and basal metabolic rate (BMR) and body composition at 3- and 6-months, respectively. Individuals held in cool conditions and fed a diet enriched with unsaturated fatty acids lost mass initially relative to the other groups, however, effects were reversible, and all individuals had a similar mass at 6- months. Chronic exposure to cool conditions increased BMR and the mass of the pectoral muscle and visceral organs. However, we could detect no long-term effect of diet on any physiological parameter. Our results contrast with those of birds studied over acute time frames, in which diet and temperature interact to determine energy expenditure. Over chronic time frames individuals appear to reach a new steady-state, with long-term physiological responses driven primarily by thermoregulatory responses to environmental temperature. Research HighlightsO_LIWith climate change, birds may encounter novel diets and temperatures C_LIO_LIIn zebra finches we show that chronic acclimation to cool temperatures increased energy expenditure and changed body composition. C_LIO_LIDietary fatty acid content had little long-term impact on the physiological parameters we measured. C_LI

zoology↗

bioRxiv2022

Unifying adaptive stress and adaptive habitat selection hypotheses through movement ecology

The cort-adaptation and cort-fitness hypotheses both propose glucocorticoids produced by parents mediate trade-offs between their own survival and that of their offspring. The contribution of glucocorticoids to offspring provisioning can quantify these trade-offs because provisioning poses a risk to parents. However, attributing provisioning behaviour to glucocorticoids is difficult because glucocorticoids often drive foraging behaviours to store energy for later provisioning. We compared the effects of glucocorticoids on habitat selection before and after calving to test for the trade-offs female elk make when provisioning offspring. Despite finding that female elk with elevated glucocorticoids selected more strongly for high-risk, high-forage cropland, we found no difference in glucocorticoid production nor a significant change in the effect of glucocorticoids on cropland selection at calving time when lactating elk required the more energy. However, we found a gradual increase in the effect of glucocorticoids on cropland selection by female elk as their calves grew, suggesting the growing energy requirements of calves encouraged more risky habitat selection behaviours by their parents over time. We suggest trade-offs in investment between parents and offspring across life history stages can be tested by integrating glucocorticoids into habitat selection models. Ultimately, this integration will help elucidate the adaptive function of glucocorticoids.

ecology↗

bioRxiv2021

Thermal flexibility is a repeatable mechanism to cope with environmental stressors in a passerine bird

O_LIFor many vertebrates, urban environments are characterised by frequent environmental stressors. Coping with such stressors can demand that urban individuals activate energetically costly physiological pathways (e.g. the fight-or-flight response) more regularly than rural-living conspecifics. However, urban environments also commonly demand appreciable expenditure toward thermoregulation, owing to their often extreme climatic variations. To date, whether and how vertebrates can balance expenditure toward both the physiological stress response and thermoregulation, and thus persist in an urbanising world, remains an unanswered and urgent question among ecologists. C_LIO_LIIn some species, changes in body surface temperature (Ts) and peripheral heat loss (qTot) that accompany the stress response are thought to balance energetic expenditure toward thermoregulation and responding to a stressor. Thus, augmentation of stressinduced thermal responses may be a mechanism by which urban individuals cope with simultaneously high thermoregulatory and stress-physiological demands. C_LIO_LIWe tested whether stress-induced changes in Ts and qTot: (1) differed between urban- and rural-origin individuals, (2) reduce thermoregulatory demands in urban individuals relative to rural conspecifics, and (3) meet an essential first criterion for evolutionary responses to selection (variability among, and consistency within, individuals). C_LIO_LIUsing the black-capped chickadee (Poecile atricapillus; n = 19), we show that neither rapid nor chronic changes in Ts and qTot following exposure to randomised stressors differed between urban- and rural-origin individuals (nurban = 9; nrural = 10). Nevertheless, we do find that stress-induced changes in Ts and qTot are highly repeatable across chronic time periods (RTs = 0.61; RqTot = 0.67) and display signatures of stabilising or directional selection (i.e. reduced variability and increase repeatability relative to controls). C_LIO_LIOur findings suggest that, although urban individuals appear no more able to balance expenditure toward thermoregulation and the stress response than rural conspecifics, the capacity to do so may be subject to selection in some species. To our knowledge this is also the first study to report repeatability of any theorised stress-induced trade-off. C_LI

ecology↗

bioRxiv2020

A temperate endotherm trades thermoregulation for self-preservation: stress-induced changes in surface temperature as thermoregulatory trade-offs

O_LICoping with stressors can require substantial energetic investment, and when resources are limited, such investment can preclude simultaneous expenditure on other biological processes. Among endotherms, energetic demands of thermoregulation can be immense, yet whether a stress response is sufficient to induce changes in thermoregulatory investment appears unexplored. C_LIO_LIWe tested the hypothesis that stress-induced changes in surface temperature, a well-documented phenomenon across vertebrates, stem from a trade-off between thermoregulation and stress responsiveness, whereby individuals seek to reduce energetic expenditure on thermoregulation in challenging environments (the "Thermoprotective Hypothesis"). We predicted that surface temperature and dry heat loss of individuals that are resource-limited would fall under stress exposure at low ambient temperatures and rise under stress exposure at high ambient temperatures when compared with non-resource limited individuals. C_LIO_LITo test our predictions, we exposed Black-capped Chickadees to rotating stressors and control treatments (ndays/treatment = 30; paired treatments) across an ambient temperature gradient whilst remotely monitoring both feeding behaviour and surface temperature. C_LIO_LISupporting the Thermoprotective Hypothesis, our results showed that: 1) social subordinates (n = 12), who fed less than social dominants and alone suffered stress-induced declines in mass, displayed significantly larger changes in surface temperature following stress exposure than social dominants (n = 8), and 2) stress-induced changes in surface temperature significantly increased heat conservation at low ambient temperature, and heat dissipation at high ambient temperature among social subordinates alone. C_LIO_LIThese results suggest that Black-capped Chickadees adjust their thermoregulatory strategies under stress when resources are limited and support the hypothesis that stress-induced changes in temperature are functionally significant. C_LI Data Availability Statement: All data and R code used for the construction of this study are available at: https://datadryad.org/stash/share/QzmRV875_S5IYpMT0jxOYIsoO-ua0T3LX6AA9u-XpdQ.

physiology↗

bioRxiv2019

Evidence that stress-induced changes in surface temperature serve a thermoregulatory function

Changes in body temperature following exposure to stressors have been documented for nearly two millennia, however, the functional value of this phenomenon is poorly understood. We tested two competing hypotheses to explain stress-induced changes in temperature, with respect to surface tissues. Under the first hypothesis, changes in surface temperature are a consequence of vasoconstriction that occurs to attenuate blood-loss in the event of injury and serves no functional purpose per se; defined as the Haemoprotective Hypothesis. Under the second hypothesis, changes in surface temperature reduce thermoregulatory burdens experienced during activation of a stress response, and thus hold a direct functional value; here, the Thermoprotective Hypothesis. To understand whether stress-induced changes in surface temperature have functional consequences, we tested predictions of the Haemoprotective and Thermoprotective hypotheses by exposing Black-capped Chickadees (n = 20) to rotating stressors across an ecologically relevant ambient temperature gradient, while non-invasively monitoring surface temperature (eye region temperature) using infrared thermography. Our results show that individuals exposed to rotating stressors reduce surface temperature and dry heat loss at low ambient temperature and increase surface temperature and dry heat loss at high ambient temperature, when compared to controls. These results support the Thermoprotective Hypothesis and suggest that changes in surface temperature following stress exposure have functional consequences and are consistent with an adaptation. Such findings emphasize the importance of the thermal environment in shaping physiological responses to stressors in vertebrates, and in doing so, raise questions about their suitability within the context of a changing climate.\n\nSummary StatementWe provide empirical evidence for a functional value to stress-induced changes in surface temperature that is consistent with an adaptation, using a temperate endotherm (Black-capped Chickadee) as a model species.

physiology↗