Body-building without power training:Endogenously regulated pectoral muscle hypertrophy in confined shorebirds

Shorebirds such as red knots Calidris canutus routinely make migratory flights of 3000 km or more. Previous studies on this species, based on compositional analyses, suggest extensive pectoral muscle hypertrophy in addition to fat storage before take-off. Such hypertrophy could be due to power train...

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Bibliographic Details
Main Authors: Dietz, M.W., Piersma, T., Dekinga, A.
Format: Article in Journal/Newspaper
Language:English
Published: 1999
Subjects:
pectoral muscle
stomach
migration
intra-individual variation
use-disuse mechanism
endogenous annual rhythm
red knot
Calidris canutus
DISTANCE MIGRANT SHOREBIRD
KNOT CALIDRIS-CANUTUS
BASAL METABOLIC-RATE
BLUE-WINGED TEAL
SKELETAL-MUSCLE
FIBER HYPERPLASIA
MASS
FLIGHT
SIZE
Red Knot
Online Access:https://hdl.handle.net/11370/53787cd7-b709-411a-88a1-d788880d083a
https://research.rug.nl/en/publications/53787cd7-b709-411a-88a1-d788880d083a
https://pure.rug.nl/ws/files/6658935/1999JExpBiolDietz.pdf
https://jeb.biologists.org/content/202/20/2831
Description
Summary:Shorebirds such as red knots Calidris canutus routinely make migratory flights of 3000 km or more. Previous studies on this species, based on compositional analyses, suggest extensive pectoral muscle hypertrophy in addition to fat storage before take-off. Such hypertrophy could be due to power training and/or be effected by an endogenous circannual rhythm. Red knots of two subspecies with contrasting migration patterns were placed in a climate-controlled aviary (12 h:12 h L:D photoperiod) where exercise was limited. Using ultrasonography, we measured pectoral muscle size as the birds stored fat in preparation for migration. At capture, there were no differences in body mass and pectoral muscle mass between the two subspecies. As they prepared for southward and northward migration, respectively, the tropically wintering subspecies (C. c. canutus) gained 31 g and the temperate wintering subspecies (C. c. islandica) gained 41 g. During this time, pectoral mass increased by 43-44% of initial mass, representing 39% (C. c. canutus) and 29% (C. c. islandica) of the increase in body mass. The gizzard showed atrophy in conjunction with a diet change from molluscs to food pellets. Although we cannot exclude the possibility that the birds' limited movement may still be a prerequisite for pectoral muscle hypertrophy, extensive power training is certainly not a requirement. Muscle hypertrophy in the absence of photoperiod cues suggests the involvement of an endogenous circannual process.

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