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Structure and Variation in the Sarcotubular System of the Extraocular Muscle Fibres in the Shark Scyliorhinus canicula L.
Author(s) -
KRYVI HARALD,
BORANDER ANNE K.,
SYVERSEN GAUTE
Publication year - 1981
Publication title -
zoologica scripta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.204
H-Index - 64
eISSN - 1463-6409
pISSN - 0300-3256
DOI - 10.1111/j.1463-6409.1981.tb00497.x
Subject(s) - scyliorhinus canicula , extraocular muscles , anatomy , biology , triad (sociology) , fish <actinopterygii> , fishery , psychology , psychoanalysis
The microscopic anatomy of the extraocular eye muscles of the shark Scyliorhinus canicula is described. In contrast to swimming muscles, the fibres are not differentiated into distinct fibre type groups. The sarcoplasmic reticulum has narrow terminal cisternae in the Z band region, longitudinal tubules and a fenestrated cisterna in the H band region. Triads or dyads are mostly located at the Z discs. A number of variations from this general pattern is described, with main emphasis on triad location, orientation and structure. Since triads in vertebrates usually are located either at the Z disc or at the A‐I junction, and with a fixed structure, these variations in shark muscles are of phylogenetic interest, as they may provide basis for an explanation of development to the two different triad locations.