Histological cross-sections of the perivertebral musculature showing the distribution of the muscle fiber types (left) and schematic illustration of the segregations of fatigue-resistant fibers (right). Data were assembled from: hagfish, Myxine glutinosa: Sudan black B staining [from , reproduced with permission of author and Springer Verlag]; velvet belly lantern shark, Etmopterus spinax: cross-section from behind the anus, Sudan black B staining (Photos by P.R. Flood, Copyright by Bathybiologica AS); tiger salamander, Ambystoma tigrinum, 4th external trunk segment, enzyme-histochemical reaction for mATPase (acid preincubation) ; desert iguana, Dipsosaurus dorsalis, 14th trunk vertebra, combined enzyme-histochemical reaction for mATPase (alkaline preincubation) and NADH-TR (S. Moritz, unpubl. data); common vole, Microtus arvalis, intervertebral level between 6th and 7th lumbar vertebrae, enzyme-histochemical reaction for mATPase (alkaline preincubation) and NADH-TR . Cross-sections were selected to illustrate of the muscular characters discussed in the text. Note that cranio-caudal changes in the proportion of the respective fiber types may occur (see text for details).