Seasonal acclimatization to temperature in cardueline finches

Abstract

1. Seasonal variation in body constituents and utilization of lipid, protein, and carbohydrate during cold stress in American goldfinches were studied to determine relations of these functions to the pronounced seasonal shift in thermogenic capacity documented in a previous study (Dawson and Carey, 1976). 2. Mean body mass for adults increases from a low of 11.4 g in July to a high of 15.1 g in December and January. Seasonal variation in lipid content accounts for the major part of the observed changes in body mass, but such variation in water and protein content is also appreciable. 3. Linoleic acid (18:2) is the predominant fatty acid in neutral lipids of liver, pectoralis muscle, and furcular depots at all seasons. Unsaturated fatty acids comprise a much greater proportion of total fatty acids in liver and pectoralis muscle during winter (71% and 73%, respectively) than in spring or fall. 4. Fasting winter goldfinches exposed to-10 ~ for 17 h overnight utilize significant amounts of body lipid. However, total body protein, liver and pectofalls muscle carbohydrate, and pectoralis muscle fatty acids do not differ significantly between control and cold-stressed individuals. 5. Glycogen stores in the pectoralis muscles are significantly higher in winter than in summer birds. Winter goldfinches exposed to-70 ~ utilize significant amounts of total body lipids and pectoralis glycogen. Birds tested in this manner in summer do not do so and quickly become hypothermic. 6. Histochemical characteristics and succinate oxidase activities of pectoralis muscles do not vary appreciably over the year. 7. Increased stores of body lipid and muscle carbohydrate and the ability to mobilize these substrates

Uncoupling Basal and Summit Metabolic Rates in White-Throated Sparrows: Digestive Demand Drives Maintenance Costs, but Changes in Muscle Mass Are Not Needed to Improve Thermogenic Capacity

“…Other cases of un-altered skeletal muscles after exposure to cold have been reported (e.g., Williams and Tieleman 2000;Tieleman et al 2003;Peña-Villalobos et al 2014), but these studies used relatively mild temperatures as their cold treatment (e.g., 157C) and did not include M sum measurements. Nonetheless, similar to our study, American goldfinches (Spinus tristis) showed an increase in M sum (Dawson and Carey 1976) with no associated changes in pectoral muscles (Carey et al 1978), and captive dark-eyed juncos (Junco hyemalis) developed a larger heart and increased their M sum in response to cold without a change in the size of their pectoral muscles (Swanson et al 2014c). Yet, other studies in both species revealed the expected changes in muscle size in association with an increase in M sum (Swanson 1991;Liknes et al 2002;Swanson et al 2014a; but see Swanson 2014b).…”

Seasonal muscle ultrastructure plasticity and resistance of muscle structural changes during temperature increases in resident black-capped chickadees (Poecile atricapillus) and rock pigeons (Columba livia)

“…It includes reversible traits such as changes in muscle mass (Liknes and Swanson, 2011). Previous studies have demonstrated that muscle mass in both black-capped chickadees and rock pigeon increases relative to body mass in colder months (Vézina et al, 2017;Petit et al, 2014;Saarela and Hohtola, 2003), although others have demonstrated no change in pectoralis muscle mass (Milbergue et al, 2018;Carey et al, 1978). Our data suggest that black-capped chickadees and rock pigeons employ differing phenotypically flexible strategies when dealing with changes across seasons.…”

“…Alteration of morphology of the pectoralis muscle is a common tactic employed by many bird species that occupy temperate regions to better match the energy demands during changing seasons (Swanson, 2010;Piersma and van Gils, 2011). Pectoralis muscle size alterations are especially pronounced between summer and winter seasons (Swanson, 1991;O'Connor, 1995;Cooper, 2002), though American goldfinches show no changes in pectoralis muscle morphology (Carey et al, 1978). Winter acclimatization in small passerine birds is frequently marked by increases in Ṁs um , and by increased thermogenic capacity, which is often correlated to 'pectoralis muscle hypertrophy' (Cooper, 2002;O'Connor, 1995;Swanson, 2010).…”

Diurnal Variation in Mass, Metabolic Rate, and Respiratory Quotient in Anna's and Costa's Hummingbirds

“…Whether the use of glycogen as a nighttime energy source by S. roseus is a unique adaptation is unclear because measurements of wholebody glycogen and its utilization are virtually nonexistent for other small birds. Mass-specific glycogen levels in S. roseus are, however, two to three times those of the American goldfinch ( Carduelis tristis; Carey et al 1978), the only other small bird for which whole-body glycogen has been determined.…”