Figure 2
From: Development of the ultrastructure of sonic muscles: a kind of neoteny?
Ultrastructure of epaxial and sonic muscles in Pygocentrus nattereri of different sizes. Ultrastructure of epaxial muscle in Pygocentrus nattereri of 3 mm (A), 25 mm (B) and 146 mm (C) length and ultrasturcture of sonic muscle from fish of 146 mm (D) length. mt: mitochondria, my: myofibril, nu: nucleus, sa: sarcoplasm, sr: sarcoplasmic reticulum, arrow head: sarcolem.