Fig. 2. Sagittal view of the mantle of a newly hatched Sepioteuthis lessoniana that shows (A) the relative proportions of superficial mitochondria-rich (SMR) and central mitochondria-poor (CMP) circular muscle fibres. Scale bar, 50 µm. A magnified view of SMR fibres is visible in B. Note the large size of the mitochondrial core (Mt) relative to the CMP cells in C. Note also that the cross-sectional area of myofilaments is not substantially different between the SMR (B) and CMP cells (C). The scale in B and C is the same. Scale bar in B, 10 µm. Bright-field microscopy of 1 µm glycol methacrylate sections stained with 1% Toluidine Blue. Mt, mitochondrion; N, nucleus.