Author ORCID Identifier

0000-0001-8235-6411 : Oliver Love

Document Type

Article

Publication Date

2-1-2020

Publication Title

American Journal of Physiology - Regulatory Integrative and Comparative Physiology

Volume

318

Issue

2

First Page

R274

Keywords

Capillaries per fiber area, Muscle fiber diameter, Muscle ultrastructure, Myonuclear domain, Phenotypic mismatch

Last Page

R283

Abstract

Phenotypic flexibility has received considerable attention in the last decade; however, whereas many studies have reported amplitude of variation in phenotypic traits, much less attention has focused on the rate at which traits can adjust in response to sudden changes in the environment. We investigated whole animal and muscle phenotypic changes occurring in black-capped chickadees (Poecile atricapillus) acclimated to cold (-5°C) and warm (20°C) temperatures in the first 3 h following a 15°C temperature drop (over 3 h). Before the temperature change, cold-acclimated birds were consuming 95% more food, were carrying twice as much body fat, and had 23% larger pectoralis muscle fiber diameters than individuals kept at 20°C. In the 3 h following the temperature drop, these same birds altered their pectoralis muscle ultrastructure by increasing the number of capillaries per fiber area and the number of nuclei per millimeter of fiber by 22%, consequently leading to a 22% decrease in myonuclear domain (amount of cytoplasm serviced per nucleus), whereas no such changes were observed in the warm-acclimated birds. To our knowledge, this is the first demonstration of such a rapid adjustment in muscle fiber ultrastructure in vertebrates. These results support the hypothesis that chickadees maintaining a cold phenotype are better prepared than warm-phenotype individuals to respond to a sudden decline in temperature, such as what may be experienced in their natural wintering environment.

DOI

10.1152/AJPREGU.00203.2019

ISSN

03636119

E-ISSN

15221490

PubMed ID

31823671

Download

Share

COinS