Muscle morphology shown as grey scale images of autofluorescence and immunofluorescence analysis of Col I as LUT images, respectively.

<p>The muscle analysed was sampled between two perimysial layers of the dorsal fillets. A) Hard muscles show a fine line of Col I between two adjacent cells (arrow) and more abundant content where more than two cells attach (asterisks). B) Col I rich fibrotic material (arrow) and total lack of endomysium (arrow head) in muscle with low firmness. C) Myocytes in a section of soft muscle appear detached and lack Col I along the stippled lines. Inset show a higher magnification with Col I along the sarcolemma of one myocyte (arrows), whereas the neighbouring cell have almost non-detectable fluorescence (arrow heads).