scholarly journals An experimental evolution study confirms that discontinuous gas exchange does not contribute to body water conservation in locusts

2016 ◽  
Vol 12 (12) ◽  
pp. 20160807 ◽  
Author(s):  
Stav Talal ◽  
Amir Ayali ◽  
Eran Gefen
Keyword(s):  
Gas Exchange ◽  
Water Loss ◽  
Experimental Evolution ◽  
Water Conservation ◽  
Locusta Migratoria ◽  
Body Water ◽  
Evaporative Water ◽  
Migratory Locust ◽  
Evolutionary Response ◽  
Evolution Study

The adaptive nature of discontinuous gas exchange (DGE) in insects is contentious. The classic ‘hygric hypothesis’, which posits that DGE serves to reduce respiratory water loss (RWL), is still the best supported. We thus focused on the hygric hypothesis in this first-ever experimental evolution study of any of the competing adaptive hypotheses. We compared populations of the migratory locust ( Locusta migratoria ) that underwent 10 consecutive generations of selection for desiccation resistance with control populations. Selected locusts survived 36% longer under desiccation stress but DGE prevalence did not differ between these and control populations (approx. 75%). Evolved changes in DGE properties in the selected locusts included longer cycle and interburst durations. However, in contrast with predictions of the hygric hypothesis, these changes were not associated with reduced RWL rates. Other responses observed in the selected locusts were higher body water content when hydrated and lower total evaporative water loss rates. Hence, our data suggest that DGE cycle properties in selected locusts are a consequence of an evolved increased ability to store water, and thus an improved capacity to buffer accumulated CO 2 , rather than an adaptive response to desiccation. We conclude that DGE is unlikely to be an evolutionary response to dehydration challenge in locusts.

Evaporative cooling in the rat: Effects of dehydration

1970 ◽  
Vol 48 (1) ◽  
pp. 18-27 ◽  
Author(s):  
Edward M. Stricker ◽  
F. Reed Hainsworth
Keyword(s):  
Heat Stress ◽  
Temperature Regulation ◽  
Water Loss ◽  
Water Conservation ◽  
Evaporative Cooling ◽  
Body Water ◽  
Large Temperature ◽  
Survival Times ◽  
Evaporative Water ◽  
Ambient Temperatures

Previous investigations demonstrated that the water loss of rats associated with increased salivary evaporation during heat stress is derived from both intracellular and intravascular sources. The present studies indicate that sufficient dehydration of either fluid compartment will impair temperature regulation. Salivary excretion from all dehydrated rats was virtually abolished at ambient temperatures below 38–40 °C, but temperature regulation was still possible if a large temperature gradient existed between the animals and the environment. Above these ambient temperatures, where increased evaporation is essential to survival, the rate of evaporative water loss returned to normal. However, body water reservoirs in dehydrated rats were rapidly depleted, salivary evaporation could not be maintained, and survival times were shortened. In contrast, access to drinking water significantly increased thermal tolerance. These results emphasize the importance of adequate body fluid hydration for evaporative cooling through saliva spreading by rats in the heat. In addition, they indicate that allocation of body water for evaporation takes precedence over conflicting demands for water conservation during heat stress.

scholarly journals Water Costs of Gas Exchange by a Speckled Cockroach and a Darkling Beetle

Insects ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 632
Author(s):  
Waseem Abbas ◽  
Philip C. Withers ◽  
Theodore A. Evans
Keyword(s):  
Body Size ◽  
Gas Exchange ◽  
Metabolic Rate ◽  
Water Loss ◽  
Evaporative Water ◽  
Factors Affecting ◽  
Darkling Beetle ◽  
Terrestrial Insects ◽  
Exchange Patterns ◽  
Respiratory Cost

Respiratory water loss during metabolic gas exchange is an unavoidable cost of living for terrestrial insects. It has been suggested to depend on several factors, such as the mode of gas exchange (convective vs. diffusive), species habitat (aridity), body size and measurement conditions (temperature). We measured this cost in terms of respiratory water loss relative to metabolic rate (respiratory water cost of gas exchange; RWL/V˙CO2) for adults of two insect species, the speckled cockroach (Nauphoeta cinerea) and the darkling beetle (Zophobas morio), which are similar in their mode of gas exchange (dominantly convective), habitat (mesic), body size and measurement conditions, by measuring gas exchange patterns using flow-through respirometry. The speckled cockroaches showed both continuous and discontinuous gas exchange patterns, which had significantly a different metabolic rate and respiratory water loss but the same respiratory water cost of gas exchange. The darkling beetles showed continuous gas exchange pattern only, and their metabolic rate, respiratory water loss and respiratory cost of gas exchange were equivalent to those cockroaches using continuous gas exchange. This outcome from our study highlights that the respiratory water cost of gas exchange is similar between species, regardless of gas exchange pattern used, when the confounding factors affecting this cost are controlled. However, the total evaporative water cost of gas exchange is much higher than the respiratory cost because cuticular water loss contributes considerably more to the overall evaporative water loss than respiratory water. We suggest that the total water cost of gas exchange is likely to be a more useful index of environmental adaptation (e.g., aridity) than just the respiratory water cost.

scholarly journals Environmental determinants of total evaporative water loss in birds at multiple temperatures

The Auk ◽  
2019 ◽  
Vol 137 (1) ◽  
Author(s):  
Soorim Song ◽  
Steven R Beissinger
Keyword(s):  
Water Loss ◽  
Water Conservation ◽  
Heat Dissipation ◽  
Natural Habitat ◽  
Thermal Conditions ◽  
Evaporative Water Loss ◽  
Diel Activity ◽  
Maximum Temperature ◽  
Arid Environments ◽  
Evaporative Water

Abstract Endotherms dissipate heat to the environment to maintain a stable body temperature at high ambient temperatures, which requires them to maintain a balance between heat dissipation and water conservation. Birds are relatively small, contain a large amount of metabolically expensive tissue, and are mostly diurnal, making them susceptible to physiological challenges related to water balance and heat dissipation. We compiled total evaporative water loss (TEWL) measurements for 174 species of birds exposed to different temperatures and used comparative methods to examine their relationships with body size, ambient temperature, precipitation, diet, and diel activity cycle. TEWL in the thermoneutral zone (TNZ) was associated primarily with body mass and activity phase. Larger and more active-phase birds, with their higher metabolic rates, lost more water through evaporation than smaller, resting-phase birds, particularly at higher thermal exposures. However, maximum temperature of the natural habitat became an important determinant of TEWL when birds were exposed to temperatures exceeding the TNZ. Species from hotter climates exhibited higher TEWL. Adaptation to arid climates did not restrict evaporative water loss at thermal conditions within the TNZ, but promoted evaporative water loss at exposures above the TNZ. The TEWL of granivores, which ingest food with low water content, differed little from species with other food habitats under all thermal conditions. The effects of environmental covariates of TEWL were dissimilar across thermal exposures, suggesting no evidence for a tradeoff between water conservation in the TNZ and heat dissipation at exposure to higher temperatures. Thus, birds may be able to acclimate when climate change results in the need to increase heat dissipation due to warming, except perhaps in hot, arid environments where species will need to depend heavily upon evaporative cooling to maintain homeothermy.

Water Metabolism of the Domestic Fowl From Hatching to Maturity

1957 ◽  
Vol 190 (1) ◽  
pp. 139-141 ◽  
Author(s):  
W. Medway ◽  
M. R. Kare
Keyword(s):  
Metabolic Rate ◽  
Basal Metabolic Rate ◽  
Water Loss ◽  
Total Body Water ◽  
Domestic Fowl ◽  
Direct Method ◽  
Body Water ◽  
Water Metabolism ◽  
Evaporative Water ◽  
Total Body

The total evaporative water loss, total body water by the direct method and the basal metabolic rate were determined on domestic fowl at various stages of growth. The trials were conducted on a total of 440 birds. The combined respiratory and cutaneous water loss was high on the 1st day of life, dropped to a minimum between 1 and 2 weeks of age, rose sharply at 2–4 weeks of age, then gradually tapered off to the value observed in the adult. The total body water and the total body water on a fat-free basis was quite high on the 1st day of life, then gradually decreased to that of the adult. The basal metabolic rate was low on the 1st day, rose sharply to a maximum at 2–4 weeks of age and then gradually tapered off to that of the adult.

scholarly journals High standing genetic variation in an invasive plant allows immediate evolutionary response to climate warming

2020 ◽  
Author(s):  
Yan Sun ◽  
Oliver Bossdorf ◽  
Ramon Diaz Grados ◽  
ZhiYong Liao ◽  
Heinz Müller-Schärer
Keyword(s):  
Climate Change ◽  
Climate Warming ◽  
Experimental Evolution ◽  
Invasive Plant ◽  
Plant Traits ◽  
Common Environment ◽  
Pooled Dna ◽  
Evolutionary Response ◽  
Evolution Study ◽  
Simulated Climate

AbstractPredicting plant distributions under climate change is constrained by our limited understanding of potential rapid adaptive evolution. In an experimental evolution study with the invasive common ragweed, we subjected replicated populations of the same initial genetic composition to simulated climate warming. Pooled DNA sequencing of parental and offspring populations showed that warming populations experienced a greater loss of genetic diversity, and greater genetic divergence from their parents, than control populations. In a common environment, offspring from warming populations showed more convergent phenotypes in seven out of nine plant traits, with later flowering and larger biomass, than plants from control populations. For both traits, we also found a significant higher ratio of phenotypic to genetic differentiation across generations for warming than for control populations, indicating stronger selection under warming conditions. Our findings demonstrate that ragweed populations can rapidly evolve in response to climate change within a single generation.

scholarly journals Does control of insensible evaporative water loss by two species of mesic parrot have a thermoregulatory role?

2020 ◽  
Vol 223 (19) ◽  
pp. jeb229930 ◽  
Author(s):  
Christine Elizabeth Cooper ◽  
Philip Carew Withers ◽  
Gerhard Körtner ◽  
Fritz Geiser
Keyword(s):  
Water Loss ◽  
Water Conservation ◽  
Arid Zone ◽  
Evaporative Water Loss ◽  
Primary Role ◽  
Physiological Control ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Physiological Variables ◽  
Regulatory Ability

ABSTRACTInsensible evaporative water loss (EWL) at or below thermoneutrality is generally assumed to be a passive physical process. However, some arid zone mammals and a single arid zone bird can control their insensible water loss, so we tested the hypothesis that the same is the case for two parrot species from a mesic habitat. We investigated red-rumped parrots (Psephotus haematonotus) and eastern rosellas (Platycercus eximius), measuring their EWL, and other physiological variables, at a range of relative humidities at ambient temperatures of 20 and 30°C (below and at thermoneutrality). We found that, despite a decrease in EWL with increasing relative humidity, rates of EWL were not fully accounted for by the water vapour deficit between the animal and its environment, indicating that the insensible EWL of both parrots was controlled. It is unlikely that this deviation from physical expectations was regulation with a primary role for water conservation because our mesic-habitat parrots had equivalent regulatory ability as the arid habitat budgerigar (Melopsittacus undulatus). This, together with our observations of body temperature and metabolic rate, instead support the hypothesis that acute physiological control of insensible water loss serves a thermoregulatory purpose for endotherms. Modification of both cutaneous and respiratory avenues of evaporation may be involved, possibly via modification of expired air temperature and humidity, and surface resistance.

Thin-skinned invaders: geographic variation in the structure of the skin among populations of cane toads (Rhinella marina)

2020 ◽  
Vol 131 (3) ◽  
pp. 611-621
Author(s):  
Georgia K Kosmala ◽  
Gregory P Brown ◽  
Richard Shine
Keyword(s):  
Geographic Variation ◽  
Water Loss ◽  
Water Conservation ◽  
Ground Substance ◽  
Skin Thickness ◽  
Native Range ◽  
Evaporative Water ◽  
Rhinella Marina ◽  
Spatial Sorting ◽  
Dry Conditions

Abstract The structure of the skin may evolve rapidly during a biological invasion, for two reasons. First, novel abiotic challenges such as hydric conditions may modify selection of traits (such as skin thickness) that determine rates of evaporative water loss. Second, invaders might benefit from enhanced rates of dispersal, with locomotion possibly facilitated by thinner (and hence more flexible) skin. We quantified thickness of layers of the skin in cane toads (Rhinella marina) from the native range (Brazil), a stepping-stone population (Hawaii), and the invaded range in Australia. Overall, the skin is thinner in cane toads in Australia than in the native range, consistent with selection on mobility. However, layers that regulate water exchange (epidermal stratum corneum and dermal ground substance layer) are thicker in Australia, retarding water loss in hot dry conditions. Within Australia, epidermal thickness increased as the toads colonized more arid regions, but then decreased in the arid Kimberley region. That curvilinearity might reflect spatial sorting, whereby mobile (thin-skinned) individuals dominate the invasion front; or the toads’ restriction to moist sites in this arid landscape may reduce the importance of water-conservation. Further work is needed to clarify the roles of adaptation versus phenotypic plasticity in generating the strong geographic variation in skin structure among populations of cane toads.

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