MORPHOMETRY OF MYOFIBER TYPES IN MUSCLES OF A BURROWING MAMMAL (Ctenomys talarum)

ALVAREZ GRACIELA ISABEL; VASSALLO ALDO; DÍAZ ALCIRA

La Plata

Congreso; IX National Congress of Morphological Sciences; 2004

Sociedad de Ciencias Morfológicas de La Plata

The purpose of this study was to analyze morphometrically the different kinds of myofiber type in two of the digging muscles (triceps lateralis and teres major) from Ctenomys talarum (Caviomorpha: Octodontidae).Myofibers were classified into types SO (slow-twitch/ oxidative), FOG (fast-twitch/ oxidative/ gycolytic) and FG (fast-twitch/ glycolytic) by differences in reactivity for myosin-ATPase (after preincubation at pH 4.35, 4.5 and 10.2), SDH and PAS. The diameters on cross-section fibers were measured and the proportion (%) and relative area (%) of each fiber type were calculated. Differences were tested for significance by mean of the X test and ANOVA.Both muscles exhibited a heterogeneous population of myofiber types (SO: 4.45 and 5.33, FOG: 55.0 and 75.53, FG: 38.55 and 19.14 for the triceps lateralis and teres major respectively), being the proportions of type FOG significantly higher (p 0.005). Fiber size was ranked with FG FOG SO. Differences between mean fiber diameters were significant (p 0.0001). The relative area of fiber type FG was higher than its proportion whereas the relative areas of fiber types FOG and SO were correspondingly lower.The muscles of Ctenomys talarum, with its heterogeneous composition of myofiber types, would allow them to face up to different functional demands (digging, aboveground locomotion, handling food) for which they must contract with varying degrees of strength. In the most specialized diggers; in contrast, the muscles tend to be more homogeneous in their fiber types composition.