Michał Wojciechowski | Nicolaus Copernicus University (original) (raw)

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Papers by Michał Wojciechowski

Basal metabolic rate (BMR) correlates with the cost of life in endothermic animals. It usually di... more Basal metabolic rate (BMR) correlates with the cost of life in endothermic animals. It usually differs consistently among individuals in a population, but it may be adjusted in response to predictable or unpredictable changes in the environment. The phenotypic flexibility of BMR is considered an adaptation to living in a stochastic environment; however, whether it is also repeatable it is still unexplored. Assuming that variations in phe-notypic flexibility are evolutionarily important, we hypothesized that they are consistently different among individuals. We predicted that not only BMR but also its flexibility in response to changes in ambient temperature (T a) are repeatable on short-and long-term timescales. To examine this, we acclimated Siberian hamsters (Phodopus sungorus) for 100 d to winterlike and then to summerlike conditions, and after each acclimation we exposed them interchangeably to 107 and 287C for 14 d. The difference in BMR measured after each exposure defined an individual's phe-notypic flexibility (DBMR). BMR was repeatable within and among seasons. It was also flexible in both seasons, but in winter this flexibility was lower in individuals responding to seasonal changes than in nonresponding ones. When we accounted for individual responsiveness, the repeatability of DBMR was significant in winter (t p 0.48, P p 0.01) and in summer (t p 0.55, P p 0.005). Finally, the flexibility of BMR in response to changes in T a was also repeatable on a long-term timescale, that is, among seasons (t p 0.31, P p 0.008). Our results indicate the evolutionary importance of the phenotypic flexibility of energy metabolism and suggest that it may be subject to selection.

As photoperiod shortens with the approach of winter, small mammals should reduce their energy exp... more As photoperiod shortens with the approach of winter, small mammals should reduce their energy expenditure to survive periods of food limitation. However, within seasons, animals should balance their energy budgets as abiotic conditions change, sometimes unpredictably; cold spells should increase heat production, while warm spells should do the opposite. Therefore, we addressed specific questions about the possible interactions between seasonal acclimatization and the intra-seasonal phenotypic flexibility of metabolic rate. We hypothesized that phenotypic flexibility in small mammals differs seasonally and is greater in summer than in winter, and predicted that seasonal adjustments in energetics, which are driven by photoperiod, overwhelm the influence of variations in the thermal environment. We measured body mass, basal metabolic rate (BMR), facultative non-shivering thermogenesis (fNST), body temperature, and calculated minimum thermal conductance in Siberian hamsters Phodopus sungorus. Animals were acclimated to winter-like, and then to summer-like conditions and, within each season, were exposed twice, for 3 weeks to 10, 20 or 28 °C. We used differences between values measured after these short acclimation periods as a measure of the scope of phenotypic flexibility. After winter acclimation, hamsters were lighter, had lower whole animal BMR, higher fNST than in summer, and developed heterothermy. After these short acclimations to the above-mentioned temperatures, hamsters showed reversible changes in BMR and fNST; however, these traits were less flexible in winter than in summer. We conclude that seasonal acclimation affects hamster responses to intra-seasonal variations in the thermal environment. We argue that understanding seasonal changes in phenotypic flexibility is crucial for predicting the biological consequences of global climate changes.

Http Dx Doi Org 10 1560 Ijee 53 2 173, Mar 14, 2013

We examined the responses of moths to an auditory stimulus in the field with respect to moth size... more We examined the responses of moths to an auditory stimulus in the field with respect to moth size, moth activity state (at rest or flying), whether it responded, and response type. Moths most commonly responded by changing flight direction. Flying moths responded significantly more often to the auditory stimulus than did resting moths; small- and medium-sized moths responded significantly more often than larger ones. We found no differences in use of response types between size classes. We suggest that these behavioral responses to the auditory stimulus are likely due to evolved induced responses to detection of predatory bats.

Small migratory birds employ a wide range of behavioural and physiological strategies to accelera... more Small migratory birds employ a wide range of behavioural and physiological strategies to accelerate their fuel accumulation rate at migratory stopovers. Although they could potentially reduce their rest-phase energy requirements by huddling with conspecifics, to date only anecdotal information exists about this behaviour. We found that resting Blackcaps (Sylvia atricapilla) regularly huddled in groups of two to six individuals in aviaries during migratory stopover. This occurred in spring migration in the Negev Desert and in autumn migration in central Poland. On some nights, huddling Blackcaps used rest-phase hypothermia, but on other nights, huddling birds maintained higher body temperatures at night than solitarily roosting individuals. Since many species of migrating passerine birds congregate at migratory stopovers, we anticipate huddling to be a common energy saving phenomenon among them.

. "Huddling reduces evaporative water loss in torpid Natterer's bats, Myotis nattereri." Comp Bio... more . "Huddling reduces evaporative water loss in torpid Natterer's bats, Myotis nattereri." Comp Biochem Physiol A Mol Integr Physiol 179: 125-132. Supplementary table 1. Raw data used for the analysis of the effect of huddling on evaporative water loss and metabolic rate of torpid Myotis nattereri.

To assess changes in body composition with changing body mass during migratory stopover, we scann... more To assess changes in body composition with changing body mass during migratory stopover, we scanned over 600 migrating birds of 21 species [body mass  50 g] using dualenergy X-ray absorptiometry (DEXA) at a stopover site at Eilat, Israel. DEXA analysis of 4 passerine species and one wader species supports the idea that fat-free mass is replenished first, and only after it asymptotes does fat mass increase. We suggest that the observed changes reflect two functional phases of body mass gain before birds recommence migration. Non-fat tissues are rebuilt first, including those subsequently necessary to restore fat, which takes place second. Seasonal differences in body composition of fruit-eating Sylvia atricapilla and Sylvia borin indicate that birds leave Eilat in spring before storing fat to maximum capacity, but close to the completion of fat-free mass regain. In contrast, S. atricapilla arrive at Eilat in autumn in the final stages of rebuilding their fat-free mass and during stopover they build-up fat stores before recommencing migration. Data for invertebrate-eating birds (Calidris minuta, Acrocephalus scirpaceus, Phylloscopus collybita and Luscinia svecica) indicate that the process of rebuilding fuel reserves is completed before leaving Eilat, both during autumn and spring migration. We suggest that because invertebrate availability is dependent on substrate and weather, invertebrate eaters opportunistically complete fueling, whereas fruits are reliably available at stopovers and frugivorous birds may have the opportunity to refuel more regularly as they progress.

Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2014

Hibernating rodents prior to winter tend to select food rich in polyunsaturated fatty acids (PUFA... more Hibernating rodents prior to winter tend to select food rich in polyunsaturated fatty acids (PUFA). Several studies found that such diet may positively affect their winter energy budget by enhancing torpor episodes. However, the effect of composition of dietary fatty acids (FA) on metabolism of normothermic heterotherms is poorly understood. Thus we tested whether diets different in FA composition affect metabolic rate (MR) and the capacity for nonshivering thermogenesis (NST) in normothermic golden hamsters (Mesocricetus auratus). Animals were housed in outdoor enclosures from May 2010 to April 2011 and fed a diet enriched with PUFA (i.e., standard food supplemented weekly with sunflower and flax seeds) or with saturated and monounsaturated fatty acids (SFA/MUFA, standard food supplemented with mealworms). Since diet rich in PUFA results in lower MR in hibernating animals, we predicted that PUFA-rich diet would have similar effect on MR of normothermic hamsters, that is, normothermic hamsters on the PUFA diet would have lower metabolic rate in cold and higher NST capacity than hamsters supplemented with SFA/MUFA. Indeed, in winter resting metabolic rate (RMR) below the lower critical temperature was higher and NST capacity was lower in SFA/MUFA-supplemented animals than in PUFA-supplemented ones. These results suggest that the increased capacity for NST in PUFA-supplemented hamsters enables them lower RMR below the lower critical temperature of the thermoneural zone.

Israel Journal of Ecology & Evolution, 2007

We examined the responses of moths to an auditory stimulus in the field with respect to moth size... more We examined the responses of moths to an auditory stimulus in the field with respect to moth size, moth activity state (at rest or flying), whether it responded, and response type. Moths most commonly responded by changing flight direction. Flying moths responded significantly more often to the auditory stimulus than did resting moths; small-and medium-sized moths responded significantly more often than larger ones. We found no differences in use of response types between size classes. We suggest that these behavioral responses to the auditory stimulus are likely due to evolved induced responses to detection of predatory bats.

Integrative and Comparative Biology, 2011

During monthly bat surveys carried out in winters of 2008/2009 and 2009/2010 we studied clusterin... more During monthly bat surveys carried out in winters of 2008/2009 and 2009/2010 we studied clustering behavior of greater mouseeared bats (Myotis myotis) hibernating in the Międzyrzecz Fortified Front (MFF) in western Poland. Since the behavior of hibernating bats is usually affected by varying environmental conditions we measured changes in the ambient temperature (Ta and water vapor pressure (WVP) and their variability in the selected areas and analyzed the relationship between clustering behavior of hibernating bats and abiotic conditions. In both winters, the number of solitarily roosting individuals of M. myotis decreased from autumn to spring while the highest number of bats hibernating in clusters was recorded in the middle of winter. The number of clusters did not change significantly over the winter, but the number of individuals within a particular cluster increased from November (median = 5, inter-quartile range, IQR = 5-8) to March (median = 20, IQR = 14-35.5). The changes of the clusters' size were best explained by a mixed model with WVP and the variability in WVP over the 20 days prior to the bat survey as explanatory variables. As WVP and the variability in WVP decreased, the number of individuals in a cluster increased. Also, Ta affected the size of clusters. However, neither of the models supported the hypothesis of the effect of variability of Ta on clustering of M. myotis. We propose that huddling enables bats to reduce evaporative water loss during the middle and at the end of the hibernation and reduces costs of spring arousals, perhaps by synchronizing them between clustered individuals and thus allowing the use of passive re-warming.

Http Dx Doi Org 10 1560 Ijee 53 2 173, Mar 14, 2013

Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2014

Israel Journal of Ecology & Evolution, 2007

We examined the responses of moths to an auditory stimulus in the field with respect to moth size... more We examined the responses of moths to an auditory stimulus in the field with respect to moth size, moth activity state (at rest or flying), whether it responded, and response type. Moths most commonly responded by changing flight direction. Flying moths responded significantly more often to the auditory stimulus than did resting moths; small-and medium-sized moths responded significantly more often than larger ones. We found no differences in use of response types between size classes. We suggest that these behavioral responses to the auditory stimulus are likely due to evolved induced responses to detection of predatory bats.

Integrative and Comparative Biology, 2011