Seppo Saarela

Daily rhythm of oxygen consumption and thermoregulatory responses in some European winter- or summer-acclimatized finches at different ambient temperatures

The oxygen consumption of European finches, the siskin (Carduelis spinus), the brambling (Fringilla montifringilla), the bullfinch (Pyrhulla pyrhulla), the greenfinch (Carduelis chloris) and the hawfinch (Coccothraustes coccothraustes), was recorded continuously while ambient temperature was decreased stepwise from +30 down to-75°C. The oxygen consumption, body temperature (telemetrically), and shivering (integrated pectoral electromyography) of greenfinches were measured simultaneously at ambient temperatures between +30 and-75°C. Maximum heat production, cold limit, lower critical temperature, basal metabolic rate and thermal conductance (of the greenfinch) were determined. The diurnal variation of oxygen consumption of siskins and greenfinches was recorded at thermoneutrality and below the thermoneutral zone in winter- and summer-acclimatized birds. The diurnal variation of body temperature and thermal conductance of greenfinches were also determined. The diurnal variation of heat production was not seasonal or temperature dependent in the siskin and in the greenfinch. Nocturnal reduction of oxygen consumption saved 15–33% energy in the siskin and greenfinch. Body temperature of the greenfinch was lowered by 2.5–3.4°C. The nocturnal reduction of thermal conductance in the greenfinch was 39–48%. The basal metabolic rate was lowest in the largest bird (hawfinch) and highest in the smallest bird (siskin). The values were in the expected range. The heat production capacity of finches in winter was 4.7 times basal metabolic rate in the siskin, 4.2 times in the brambling, 3.5 times in the greenfinch and 2.9 times in the bullfinch and hawfinch. The heat production capacity of the siskin and greenfinch was not significantly lower in summer. The cold limit temperatures (°C) in winter were-61.2 in the siskin,-41.3 in the greenfinch,-37.0 in the bullfinch,-35.7 in the brambling and-28.9 in the hawfinch. The cold limit was 14.3°C higher in summer than in winter in the siskin and 8.7°C in the greenfinch. Thermal insulation of the greenfinch was significantly better in winter than in summer. The shivering of the greenfinch increased linearly when ambient temperature was decreased down to-40°C. Maintenance of shivering was coincident with season. In severe cold integrated pectoral electromyography did not correlate with oxygen consumption as expected. The possible existence of non-shivering thermogenesis in birds is discussed. It is concluded that the acclimatization of European finches is primarily metabolic and only secondly affected by insulation.

Nocturnal hypothermia in fasting Japanese quail: The effect of ambient temperature

Japanese quail were equipped with intraperitoneal transmitters for telemetric measurement of body temperature (Tb) and activity. Food deprivation at + 24 degrees C for four days induced a well-defined nocturnal hypothermic response. The normal day-night difference (about 1 degrees C) in Tb increased 1 degrees C per day, reaching 5 degrees C on the fourth night of fast. Nocturnal motor activity decreased during the fast, while daytime activity first increased and then returned to the original level by the end of the fasting period. A strong correlation between Tb and motor activity was found during scotophase (r = .91) but not during photophase (r = .02). At + 4 degrees C, where food was deprived for two days, the level of hypothermia was not different from that at + 24 degrees C, but birds fasting in the cold reached the hypothermic level more rapidly. In control birds, the decrease in Tb at the beginning of scotophase was independent of ambient temperature. In the combined data, the level of hypothermia correlated strongly with body mass loss (r = .90), which shows that quail can directly or indirectly sense the amount of body energy reserves. This is the first report of hypothermia in a fasting gallinaceous bird. The consistent level of hypothermia at varying ambient temperatures suggests that either nonenergetic costs or phylogenetic constraints prevent deeper hypothermia in cold. Accordingly, the regulation of hypothermia cannot be explained by using only energetic arguments.

Summer and Winter Temperature Regulation in the Black Grouse Lyrurus tetrix

Metabolic rate and thermal responses to ambient temperatures between -26.5 C and 34.0 C were studied in the adult black grouse in both summer and winter, and in juvenile (70-80 days old) black grouse in early autumn. At an ambient temperature between 0 C and 20 C, the body temperature of the adult grouse was significantly higher in summer (41.3 ± .09 C) than in winter (40.2 ± .14 C). The standard metabolism at thermoneutrality was 6.5 W/kg in summer and 8.2 W/kg in winter, being higher in both seasons than predicted by theoretical equations. The lower critical temperature was 9.5-12.5 C in summer and around 5 C in winter. However, no clear inflection point was seen in the metabolism in winter. The increase in metabolic rate was only 1.7-fold in winter and 2.2-fold in summer when ambient temperature decreased from 30 C to -23 C. At ambient temperatures ranging from 10 C to -23 C the thermal conductance was higher in winter than in summer; in winter, but not in summer, it decreased with decreasing ambient temperature. The assumption is that in winter the black grouse improve their insulation also at ambient temperature far below the lower critical temperature.

Effect of photoperiod and melatonin on cold resistance, thermoregulation and shivering/nonshivering thermogenesis in Japanese quail

SummaryThe effect of photoperiod and melatonin treatment on cold resistance and thermogenesis of quails was studied. The birds were acclimated for 8 weeks to short day (8L:16D) or long day (16L:8D) conditions, and 8 of 16 quails in each group were implanted with melatonin capsules. One group of quails was maintained outside in an aviary during winter. Oxygen consumption (

Annual variation in the concentrations of circulating hormones in capercaillie (Tetrao urogallus)

\dot V_{O_2 }

The effect of myocardial infarction on the synthesis, concentration and receptor expression of endogenous melatonin.

) body temperature (Tb, recorded with temperature transmitters) and shivering (integrated pectoral EMG) were recorded continuously, and samples of heart rate and breathing rate were picked up when ambient temperature was decreased stepwise from 27 down to −75 °C. Heat production maximum (HPmax), cold limit, lower critical temperature, basal metabolic rate (BMR) and thermal conductance were determined.The results show that short day, cold and melatonin treatment improved cold resistance and thermal insulation of quils when compared with quails acclimated to long day conditions. An increase in HPmax was induced only by melatonin treatment. The results suggest that the acclimatization of quails is under control of the pineal gland.The linear increase of shivering intensity with

Plasma urea, creatinine, and urea: creatinine ratio in reindeer (Rangifer tarandus tarandus) and in Svalbard reindeer (Rangifer tarandus platyrhynchus) during defined feeding conditions and in the field.

\dot V_{O_2 }