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Histochemical Characterization and Distribution of Fiber Types in the Pectoralis Muscle of the Ostrich ( Struthio camelus ) and Emu ( Dromaius novaehollandiae )
Author(s) -
Rosser Benjamin W. C.,
George John C.
Publication year - 1985
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1985.tb00839.x
Subject(s) - struthio , biology , sexual dimorphism , anatomy , pectoralis muscle , myofibril , zoology , endocrinology
The muscle fibers of the pectoralis (M. pectoralis pars thoracicus) of a male and a female ostrich ( Struthio camelus ) and a male and a female emu ( Dromaius novaehollandiae ) were studied histochemically for succinate dehydrogenase and myofibrillar adenosine triphosphatase. Slow‐tonic (ST), fast‐twitch oxidative‐glycolytic (FOG) and fast‐twitch glycolytic (FG) fibers were approximately equal in number and distribution in the emu pectoralis examined. In the ostriches, both predominantly FG and approximately equal areas, were present. ST fibers were significantly ( P ≤ 0.05) larger than the similarly ( P ≥ 0.05) sized FG and FOG fibers in the female ostrich and emus. In the male ostrich ST fibers were smaller ( P ≤ 0.05) than FG fibers, neither of which were significantly ( P ≥ 0.05) different from FOG fibers. The ratites have the greatest percentage and widest distribution of ST fibers found in any avian pectoralis studied to date. This could represent the ancestoral avian pectoralis, neoteny or an effect of flightlessness. ST fibers are used in the maintenance of posture, which is probably the main role of the pectoralis in the emu. The predominantly FG areas of the ostrich are indicative of an additional function, namely, behavioural display. Sexual dimorphism in the ostrich pectoralis is strongly suggested.