Rubber latex yield and physiology of rubber tree with tea tree oil treatments

To examine the effects of tea tree oil on rubber latex yield and the resulting latex physiological parameters of rubber tree （Hevea brasiliensis），clean water and 20%，40%，60%，80% and 100% of tea tree oil were applied on the tapping cut of rubber trees. The data were analyzed by Duncan test and its results showed that when compared to clean water （ck），80% and 100% of tea tree oil stimulation significantly promoted rubber latex yield（P＜0.05）. In addition，the latex physiological parameters changed with the sucrose content（P＜0.01），magnesium ion content （P＜0.01） and inorganic phosphorus content （P＜0.01） of latex significantly increasing and thiol content significantly deceasing （P＜0.01）. The effect of tea tree oil treatments on rubber yield was similar to the impact of 0.5% ethrel stimulation. However，compared to ethrel stimulation，100% tea tree oil treatment significantly increased dry rubber and sucrose contents （P＜0.01） and decreased thiol content （P＜0.01）. Thus，tea tree oil treatment involved different latex yield promotion mechanisms than that of ethrel stimulation.

The effect of prescribed fluid consumption on physiology and work behavior of wildfire fighters

The purpose of this study was to examine 1) wildfire fighters' ability to consume the prescribed fluid volume (1200 mL h-1), 2) the effect of fluid intake on plasma sodium and hydration, and 3) the effect of fluid intake on firefighters' heart rate, core temperature and activity during emergency suppression shifts. Methods: Thirty-four firefighters were divided into ad libitum (AD, n = 17) and prescribed (PR, n = 17) drinking groups. Results: PR drinkers did not meet the prescribed fluid target, yet consumed over double the volume of AD drinkers. No differences between groups in plasma sodium or hydration were noted. PR drinking resulted in lower core temperature between 2 and 6 h. This did not coincide with reduced cardiovascular strain, greater work activity or larger distances covered when compared to AD drinkers. Conclusion: Extra fluid consumption (above AD) did not improve firefighter activity or physiological function (though PR firefighters core temperature was lower earlier in their shift). Firefighter can self-regulate their fluid consumption behavior and work rate to leave the fireground euhydrated.

Seasonal stress physiology and body condition differ among co-occurring tropical finch species.

Seasonal changes in avian hormonal stress responses and condition are well known for common species found at temperate and arctic latitudes, but declining and tropical species are poorly studied. This study compares stress and condition measures of co-occurring declining and non-declining tropical grass finch species in Australia. We monitored declining Gouldian finches (Erythrura gouldiae) and non-declining long-tailed and masked finches (Poepila acuticauda and P. personata) during two seasons that are potentially stressful: peak breeding (early dry season when food is plentiful) and moult (late dry to early wet season when food may be scarce). We measured body condition (muscle and fat), haematocrit, and stress response to capture using plasma corticosterone and binding globulin concentrations. All species had higher muscle and lower fat indices during breeding than moult. Haematocrit did not consistently differ between seasons. Long-tailed finches had higher stress responses during breeding than moult, similar to other passerines studied. Masked finches showed no seasonal changes in stress response. Gouldian finches had stress response patterns opposite to those of long-tailed finches, with higher stress responses during moult. However, seasonal trends in Gouldian and long-tailed finch stress responses sometimes differed between years or sites. The differences in stress response patterns between species suggest that the declining Gouldian finch is more sensitive to recent environmental changes which are thought to further reduce grass seed food resources during the late dry to early wet season. Retention of stress responsiveness during a protracted moult could increase the survival potential of Gouldian finches. This study highlights the utility of stress and condition indices to determine the sensitivity of co-occurring species to environmental conditions.

Developmental stress can uncouple relationships between physiology and behaviour

Phenotypic correlations (rP) have frequently been observed between physiological and behavioural traits, and the nature of these associations has been shown to be modulated by a range of environmental stressors. Studies to date have examined the effects of acute stressors on physiology-behaviour interrelations, but the potential for permanent changes induced by exposure to stress during development remains unexplored. We exposed female zebra finches to dietary restriction during the nestling stage and tested how this affected rP among a variety of physiological traits (haematocrit, stress-induced corticosterone level and basal metabolic rate (BMR)) and behavioural traits (activity and feeding rates in novel and familiar environments). Developmental stress completely uncoupled the relationship between activity in a novel environment and two physiological traits: haematocrit and BMR. This suggests that nutritionally based developmental stress has provoked changes in the energy budget that alleviate the trade-off between maintenance (BMR) and locomotor activities.

Effect of heat on firefighters' work performance and physiology

Wildland firefighters often perform their duties under both hot and mild ambient temperatures. However, the direct impact of different ambient temperatures on firefighters' work performance has not been quantified. This study compared firefighters' work performance and physiology during simulated wildland firefighting work in hot (HOT; 32°C, 43% RH) and temperate (CON; 19°C, 56% RH) conditions. Firefighters (n=38), matched and allocated to either the CON (n=18) or HOT (n=20) condition, performed simulated self-paced wildland fire suppression tasks (e.g., hose rolling/dragging, raking) in firefighting clothing for six hours, separated by dedicated rest breaks. Task repetitions were counted (and converted to distance or area). Core temperature (Tc), skin temperature (Tsk), and heart rate were recorded continuously throughout the protocol. Urine output was measured before and during the protocol, and urine specific gravity (USG) analysed, to estimate hydration. Ad libitum fluid intake was also recorded. There were no differences in overall work output between conditions for any physical task. Heart rate was higher in the HOT (55±2% HRmax) compared to the CON condition (51±2% HRmax) for the rest periods between bouts, and for the static hose hold task (69±3% HRmax versus 65±3% HRmax). Tc and Tsk were 0.3±0.1°C and 3.1±0.2°C higher in the HOT compared to the CON trial. Both pre- and within- shift fluid intake were increased two-fold in the heat, and participants in the heat recorded lower USG results than their CON counterparts. There was no difference between the CON and HOT conditions in terms of their work performance, and firefighters in both experimental groups increased their work output over the course of the simulated shift. Though significantly hotter, participants in the heat also managed to avoid excessive cardiovascular and thermal strain, likely aided by the frequent rest breaks in the protocol, and through doubling their fluid intake. Therefore, it can be concluded that wildland firefighters are able to safely and efficiently perform their duties under hot conditions, at least over six hours.

Fluid intake, hydration, work physiology of wildfire fighters working in the heat over consecutive days

PURPOSE: (i) To evaluate firefighters' pre- and post-shift hydration status across two shifts of wildfire suppression work in hot weather conditions. (ii) To document firefighters' fluid intake during and between two shifts of wildfire suppression work. (iii) To compare firefighters' heart rate, activity, rating of perceived exertion (RPE), and core temperature across the two consecutive shifts of wildfire suppression work. METHOD: Across two consecutive days, 12 salaried firefighters' hydration status was measured immediately pre- and post-shift. Hydration status was also measured 2h post-shift. RPE was also measured immediately post-shift on each day. Work activity, heart rate, and core temperature were logged continuously during each shift. Ten firefighters also manually recorded their food and fluid intake before, during, and after both fireground shifts. RESULTS: Firefighters were not euhydrated at all measurement points on Day one (292±1 mOsm l(-1)) and euhydrated across these same time points on Day two (289±0.5 mOsm l(-1)). Fluid consumption following firefighters' shift on Day one (1792±1134ml) trended (P = 0.08) higher than Day two (1108±1142ml). Daily total fluid intake was not different (P = 0.27), averaging 6443±1941ml across both days. Core temperature and the time spent ≥ 70%HRmax were both elevated on Day one (when firefighters were not euhydrated). Firefighters' work activity profile was not different between both days of work. CONCLUSION: There was no difference in firefighters' pre- to post-shift hydration within each shift, suggesting ad libitum drinking was at least sufficient to maintain pre-shift hydration status, even in hot conditions. Firefighters' relative hypohydration on Day one (despite a slightly lower ambient temperature) may have been associated with elevations in core temperature, more time in the higher heart rate zones, and 'post-shift' RPE.

Multiple days of heat exposure on firefighters' work performance and physiology

This study assessed the accumulated effect of ambient heat on the performance of, and physiological and perceptual responses to, intermittent, simulated wildfire fighting tasks over three consecutive days. Firefighters (n = 36) were matched and allocated to either the CON (19°C) or HOT (33°C) condition. They performed three days of intermittent, self-paced simulated firefighting work, interspersed with physiological testing. Task repetitions were counted (and converted to distance or area) to determine work performance. Participants were asked to rate their perceived exertion and thermal sensation after each task. Heart rate, core temperature (Tc), and skin temperature (Tsk) were recorded continuously throughout the simulation. Fluids were consumed ad libitum. Urine volume was measured throughout, and urine specific gravity (USG) analysed, to estimate hydration. All food and fluid consumption was recorded. There was no difference in work output between experimental conditions. However, significant variation in performance responses between individuals was observed. All measures of thermal stress were elevated in the HOT, with core and skin temperature reaching, on average, 0.24 ± 0.08°C and 2.81 ± 0.20°C higher than the CON group. Participants' doubled their fluid intake in the HOT condition, and this was reflected in the USG scores, where the HOT participants reported significantly lower values. Heart rate was comparable between conditions at nearly all time points, however the peak heart rate reached each circuit was 7 ± 3% higher in the CON trial. Likewise, RPE was slightly elevated in the CON trial for the majority of tasks. Participants' work output was comparable between the CON and HOT conditions, however the performance change over time varied significantly between individuals. It is likely that the increased fluid replacement in the heat, in concert with frequent rest breaks and task rotation, assisted with the regulation of physiological responses (e.g., heart rate, core temperature).

Tough decisions: Reproductive timing and output vary with individuals' physiology, behavior and past success in a social opportunistic breeder

This article is part of a Special Issue SBN 2014. Photoperiod and the hormonal response it triggers are key determinants of reproductive timing in birds. However, other cues and physiological traits may permit flexibility in the timing of breeding and perhaps facilitate adaptation to global change. Opportunistic breeders are excellent models to study the adaptive significance of this flexibility, especially at the individual level. Here, we sought to quantify whether particular male physiological and behavioral traits were linked to reproductive timing and output in wild-derived zebra finches. We repeatedly assessed male stress-induced corticosterone levels (CORT), basal metabolic rate (BMR), and activity before releasing them into outdoor aviaries and quantifying each pair's breeding timing, investment, and output over a seven-month period. Despite unlimited access to food and water, the colony breeding activity occurred in waves, probably due to interpair social stimulations. Pairs adjusted their inter-clutch interval and clutch size to social and temperature cues, respectively, but only after successful breeding attempts, suggesting a facultative response to external cues. When these effects were controlled for statistically or experimentally, breeding intervals were repeatable within individuals across reproductive attempts. In addition, males' first laying date and total offspring production varied with complex interactions between pre-breeding CORT, BMR and activity levels. These results suggest that no one trait is under selection but that, instead, correlational selection acts on hormone levels, metabolism, and behavior. Together our results suggest that studying inter-individual variation in breeding strategy and their multiple physiological and behavioral underpinnings may greatly improve our understanding of the mechanisms underlying the evolution of breeding decisions.