Affiliation:
1. Colgate University, Department of Biology, 13 Oak Dr., Hamilton, NY 13346, USA
2. Hamilton College, Department of Biology, 198 College Hill Rd., Clinton, NY 13323, USA
Abstract
Resident birds in temperate zones respond to seasonally fluctuating temperatures by adjusting their physiology, such as changes in basal metabolic rate (BMR) or peak metabolic rate during cold exposure (Msum), or altering their organ sizes, so as to match the thermogenic requirements of their current environment. Climate change is predicted to show increases in the frequency of heat and cold wave events, which could increase the likelihood that birds will face environmental mismatch. Here, we examined seasonality and the effects of acute and chronic heat shock to 33 °C and subsequent recovery from heat shock on the ultrastructure of the superficial pectoralis muscle fiber diameter, myonuclear domain (MND), and capillary density in two temperate bird species of differing body masses, the black-capped chickadee (Poecile atricapillus) and the rock pigeon (Columba livia). We found that muscle fiber ultrastructure did not change with heat treatment. However, in black-capped chickadees, there was a significant increase in fiber diameter in spring phenotype birds compared with summer phenotype birds. In rock pigeons, we saw no differences in fiber diameter across seasons. Capillary density did not change as a function of fiber diameter in black-capped chickadees, but did change seasonally, as did MND. Across seasons, as fiber diameter decreased, capillary density increased in the pectoralis muscle of the rock pigeons. For both species in this study, we found that as fiber diameter increases so does MND. Our findings imply that these two temperate birds employ different muscular growth strategies that may be metabolically beneficial to each.
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
Cited by
14 articles.
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