The stoichiometric approach in determining total evaporative water loss and the relationship between evaporative and non-evaporative heat loss in two resting bird species: passerine and non-passerine

Abstract

The stoichiometric approach in determining total evaporative water loss and the relationship between evaporative and non-evaporative heat loss in two resting bird species: passerine and non-passerine GavrilovGavrilov Avian Res (2015) 6:19 DOI 10.1186 RESEARCHThe stoichiometric approach in determining total evaporative water loss and the relationship between evaporative and non-evaporative heat loss in two resting bird species: passerine and non-passerine Valery M. Gavrilov * Abstract Background: Evaporation is of significant ecological interest. Evaporation from an animal always results in a decrease in the temperature of the surface from which the evaporation occurs. Therefore, evaporation is a one-way transfer which causes heat loss from the organism. Biological evaporation always involves the loss of water which is a vital resource for nearly all biochemical processes. Evaporation is loss of heat via loss of body mass. Methods:The simultaneous determination of energy expenditure and loss of body mass in resting birds allows us to estimate evaporative heat loss. This method includes direct measurements of the energetic equivalent of the loss of body mass as the ratio between heat production, determined by the rate of oxygen consumption and the loss of body mass at various ambient temperatures. Results:The data indicate that evaporation was minimal at lower critical temperature and that the rate of evaporation increased at lower or higher temperatures. Obtained results indicate that passerine and non-passerine species have the ability to change their non-evaporative heat conductance the same number of times (approximately fourfold), and that their abilities in this respect are similar. Conclusions:The novelty of the study resides in the stoichiometric approach to determination of total evaporative water loss. The analysis shows that determinations by stoichiometric approach of total evaporative water loss yielded the values, which fit into the confidence intervals of all equations from literatures. The basal metabolic rate and nonevaporative thermal conductance are fundamental parameters of energetics and determine the level of physiological organization of an endothermic animal.

Scaling of total evaporative water loss and evaporative heat loss in birds at different ambient temperatures and seasons

“…I performed preliminary experiments to determine the time of a day (in 24-hour cycle) when the loss of body mass of the bird was minimal and bird's rate of metabolism was constant. Our data for some species were consistent with the results of previous experiments, [4][5][6][7]17,26 and suggests that mass losses resulting from cloacal excretions and products of nitrogen metabolism remain very small under these experimental conditions and may be ignored. Therefore, the main variable affecting the q value is the pulmonary and cutaneous evaporation of water.…”

“…At 0°C and T lс , the lines describing the effects of the evaporative and non-evaporative heat losses on the body mass do not intersect in the range of real sizes; however, at T uc , the lines of regression for H e and H s intersect at a body mass of approximately 25g in Passeriformes. [6][7][8] These facts show that relatively larger passerine birds at high ambient temperatures find it more difficult to maintain their heat balance. These birds must use additional water evaporation to maintain their heat balance.…”

“…, q where q is in W/g (7) Equation (7) facilitates the calculation of %H e for specific q values for fat metabolism, determined during the winter. Evaporative heat loss for any combination of oxidized compounds can be calculated using this method.…”

“…All of the obtained data on heat loss at rest (BMR) and the associated values measured (q, H e , and TEWL) for all bird species for two seasons are summarized in Table 2. Most of the BMRs measurements results have been published in reviews, [6][7][8]17,27 and entered into the critical analysis of Makarieva et al, 2008, 29 McNab. 13 As an example, the obtained values of energy metabolism in summer for one of the passerine species, the Chaffinch (Fringilla coelebs), are also presented in graphic.…”

“…A major disadvantage of the direct weighing method is that it does not permit the simultaneous determination of the energetic cost of evaporative cooling by monitoring oxygen consumption or carbon dioxide production, as is possible in the open flow method. As previous studies have shown, [4][5][6][7] it is possible to determine evaporative heat loss from the ratio (q) between heat production (RM) (determined by the rate of oxygen consumption) and body mass loss (Dm) at various ambient temperatures (T A ): q=RM/Dm. High water loss necessitates regular water ingestion through drinking, consuming water in food, and metabolic water production.…”