scholarly journals Integrating bioenergetics and conservation biology: thermal sensitivity of digestive performance in Eastern Collared Lizards (Crotaphytus collaris) may affect population persistence

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Casey L Brewster ◽  
Jason Ortega ◽  
Steven J Beaupre
Keyword(s):  
Thermal Sensitivity ◽  
Metabolizable Energy ◽  
Effect Of Temperature ◽  
Valuable Insight ◽  
Feeding Rates ◽  
Crotaphytus Collaris ◽  
Reduced Body ◽  
Heat Loads ◽  
Passage Times ◽  
Collared Lizards

Abstract Information on bioenergetics can provide valuable insight into the ecology, life history and population dynamics of organisms. For ectothermic animals, thermal sensitivity of digestion is an important determinant of net assimilated energy budgets. A recent study in the Ozark Mountains indicated that eastern collared lizards (Crotaphytus collaris) restricted to encroached glades (characterized by woody vegetation encroachment) experience reduced environmental heat loads and have reduced age-specific growth and reproductive rates compared to populations in intact glades. To assess the potential impact of reduced body temperatures on assimilation rates of C. collaris in encroached glades, we conducted feeding trials across four temperature treatments (28, 31, 34 and 37°C). We tested for temperature effects on voluntary feeding rates, passage times, apparent assimilated energy (AE) and metabolizable energy (ME). Passage times decreased and voluntary feeding rates increased significantly with increasing temperature. Consumption explained the majority of variance in AE and ME, followed by the effect of temperature treatments. Using data on voluntary feeding rates, passage times and ME as a function of temperature, we estimated over a 10-fold increase in predicted daily assimilated energy across temperature treatments (28°C = 0.58 kJ/day, 31°C = 1.20 kJ/day, 34°C = 4.30 kJ/day, 37°C = 7.95 kJ/day). Thus, lower heat loads in encroached glades may cause reduced body temperature and result in restricted energy assimilation rates. Our study provides a novel approach to the integration of bioenergetics and conservation and shows the efficacy of using information on digestive performance to investigate underlying mechanisms in a conservation context.

scholarly journals Geographical and Seasonal Thermal Sensitivity of Grazing Pressure by Microzooplankton in Contrasting Marine Ecosystems

2021 ◽  
Vol 12 ◽  
Author(s):  
Marco J. Cabrerizo ◽  
Emilio Marañón
Keyword(s):  
Thermal Sensitivity ◽  
Grazing Pressure ◽  
Open Ocean ◽  
Effect Of Temperature ◽  
Extensive Literature ◽  
Thermal Dependence ◽  
Food Web Structure ◽  
Element Cycling ◽  
Large Variability ◽  
Microzooplankton Grazing

Grazing pressure, estimated as the ratio between microzooplankton grazing and phytoplankton growth rates (g:μ), is a strong determinant of microbial food-web structure and element cycling in the upper ocean. It is generally accepted that g is more sensitive to temperature than μ, but it remains unknown how the thermal dependence (activation energy, Ea) of g:μ varies over spatial and temporal scales. To tackle this uncertainty, we used an extensive literature analysis obtaining 751 paired rate estimates of μ and g from dilution experiments performed throughout the world’s marine environments. On a geographical scale, we found a stimulatory effect of temperature in polar open-ocean (∼0.5 eV) and tropical coastal (∼0.2 eV) regions, and an inhibitory one in the remaining biomes (values between −0.1 and −0.4 eV). On a seasonal scale, the temperature effect on g:μ ratios was stimulatory, particularly in polar environments; however, the large variability existing between estimates resulted in non-significant differences among biomes. We observed that increases in nitrate availability stimulated the temperature dependence of grazing pressure (i.e., led to more positive Ea of g:μ) in open-ocean ecosystems and inhibited it in coastal ones, particularly in polar environments. The percentage of primary production grazed by microzooplankton (∼56%) was similar in all regions. Our results suggest that warming of surface ocean waters could exert a highly variable impact, in terms of both magnitude and direction (stimulation or inhibition), on microzooplankton grazing pressure in different ocean regions.

scholarly journals Survivable hypothermia or torpor in a wild-living rat: rare insights broaden our understanding of endothermic physiology

2021 ◽  
Author(s):  
Julia Nowack ◽  
Christopher Turbill
Keyword(s):  
Body Temperature ◽  
Data Sets ◽  
Valuable Insight ◽  
Limited Capacity ◽  
Probability Of Survival ◽  
Reduced Body ◽  
Rattus Fuscipes ◽  
Evolutionary Pathways ◽  
Term Data

AbstractMaintaining a high and stable body temperature as observed in endothermic mammals and birds is energetically costly. Thus, it is not surprising that we discover more and more heterothermic species that can reduce their energetic needs during energetic bottlenecks through the use of torpor. However, not all heterothermic animals use torpor on a regular basis. Torpor may also be important to an individual’s probability of survival, and hence fitness, when used infrequently. We here report the observation of a single, ~ 5.5 h long hypothermic bout with a decrease in body temperature by 12 °C in the native Australian bush rat (Rattus fuscipes). Our data suggest that bush rats are able to rewarm from a body temperature of 24 °C, albeit with a rewarming rate lower than that expected on the basis of their body mass. Heterothermy, i.e. the ability to withstand and overcome periods of reduced body temperature, is assumed to be an evolutionarily ancestral (plesiomorphic) trait. We thus argue that such rare hypothermic events in species that otherwise appear to be strictly homeothermic could be heterothermic rudiments, i.e. a less derived form of torpor with limited capacity for rewarming. Importantly, observations of rare and extreme thermoregulatory responses by wild animals are more likely to be discovered with long-term data sets and may not only provide valuable insight about the physiological capability of a population, but can also help us to understand the constraints and evolutionary pathways of different phenologies.

Comparative Field Energetics of Two Macropod Marsupials and a Ruminant.

1990 ◽  
Vol 17 (6) ◽  
pp. 591 ◽  
Author(s):  
KA Nagy ◽  
GD Sanson ◽  
NK Jacobsen
Keyword(s):  
Feeding Rate ◽  
Energy Content ◽  
Metabolizable Energy ◽  
Ecological Modelling ◽  
Feeding Rates ◽  
Doubly Labelled Water ◽  
Water Influx ◽  
Scaling Relationship ◽  
Field Metabolic Rates ◽  
Free Ranging

Field metabolic rates (FMRs) and water influx rates were measured via the doubly labelled water method in wild Tasmanian pademelons and grey kangaroos living in the Jock Marshall Reserve at Clayton, Victoria, and in wild black-tailed deer free-ranging within a nature reserve at Davis, California. Deer expended more than 3 times more energy per day than similar sized grey kangaroos. Feeding rates required to achieve energy balance were estimated from FMRs along with an estimate of metabolizable energy content of the food. The estimated feeding rates for pademelons and kangaroos were combined with similar values for 5 other species of macropods to calculate an allometric (scaling) relationship for food requirements of macropod marsupials. Feeding rate had the following relationship to body mass: g food (DM) consumed per day = 0.20 g body mass0.79 (r2 = 0.94). The findings reported herein should be useful for predicting the approximate food requirements of free-ranging macropods and deer for purposes of ecological modelling, conservation efforts and management programmes.

Effect of temperature on glyceryl trinitrate induced relaxation of rabbit aorta

1993 ◽  
Vol 71 (8) ◽  
pp. 629-632 ◽  
Author(s):  
Brian P. Booth ◽  
James F. Brien ◽  
Gerald S. Marks ◽  
Kanji Nakatsu
Keyword(s):  
Nitric Oxide ◽  
Cardiopulmonary Bypass ◽  
Glyceryl Trinitrate ◽  
Rabbit Aorta ◽  
Tissue Response ◽  
Effect Of Temperature ◽  
Hypothermic Cardiopulmonary Bypass ◽  
Reduced Body ◽  
Vasodilatory Response ◽  
Two Temperatures

It has previously been shown that the vasodilatory response to glyceryl trinitrate (GTN) was decreased during hypothermic cardiopulmonary bypass. The purpose of these experiments was to determine the effect of temperature on GTN-induced relaxation and on GTN biotransformation in rabbit aorta. It was determined that the EC50 of GTN on rabbit aortic rings (RARs) was increased significantly from 1.8 × 10−8 M at 37 °C to 3.4 × 10−8 M at 27 °C (p < 0.05). The production of NO by rabbit aortic strips (RASs) was significantly less at 27 °C compared with 37 °C after 80 min, being 9.62 × 10−11 ± 13.2 × 10−11 mol NO/g wet wt. RASs compared with 5.71 × 10−10 ± 9.43 × 10−11 mol NO/g wet wt. RASs, respectively (p < 0.05), after 80 min incubation. There was no difference in the amount of glyceryl-1,2-dinitrate (1,2-GDN) produced from GTN at the two temperatures. The ED20 for NO-induced relaxation of RARs increased from 3.46 × 10−10 ± 2.24 × 10−10 mol at 37 °C to 1.01 × 10−9 ± 4.51 × 10−10 mol at 27 °C (p < 0.05). These data indicate that the biotransformation of GTN and the release of NO were impaired by hypothermia, and that this, as well as a decrease in the tissue response to NO at 27 °C, explains the decrease in GTN activity at reduced body temperatures.Key words: glyceryl trinitrate, nitric oxide, temperature, rabbit aorta, vasodilation.

scholarly journals Effect of Ambient Temperature on the Performance of Shaver Brown Hens in Hot Humid Environment

2019 ◽  
pp. 1-10
Author(s):  
A. O. Ani ◽  
M. O. Okpara
Keyword(s):  
Ambient Temperature ◽  
Egg Production ◽  
Shape Index ◽  
Metabolizable Energy ◽  
Effect Of Temperature ◽  
Crude Fibre ◽  
Egg Weight ◽  
Humid Environment ◽  
Egg Shape ◽  
Egg Shell

The effect of temperature on the performance of Shaver brown hens in the hot humid environment was investigated using seventy-five Shaver brown hens in their 14th week of lay. Each hen was housed in individual battery cage and fed daily with 125 g of commercial layers mash containing 16.5% crude protein, 2650 kcal/kg metabolizable energy, 4% crude fat, 6.5% crude fibre, 3.6% calcium and 0.4% phosphorus for 10 weeks. Water was supplied ad libitum to the birds. Eggs were collected daily and recorded for each hen. Data were collected on average daily feed intake(ADFI),  egg weight, eggshell weight, egg shell thickness, egg shape index, albumin height, yolk height, albumin index, yolk index, haugh unit and hen day egg production. Results showed that ADFI, hen day egg production, egg shape index, albumin height, yolk height, yolk index and Haugh units were significantly (P < 0.05) decreased with increase in ambient temperature. However, high ambient temperature did not have significant (P > 0.05) effect on egg weight, eggshell thickness and albumin index. Based on the results obtained in the study, it was concluded that ambient temperature had an effect on the performance of Shaver brown hens in the humid tropics.

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