Fig. 3. Sagittal view of the mantle of a juvenile Sepioteuthis lessoniana that shows (A) the relative proportions of superficial mitochondria-rich (SMR) and central mitochondria-poor (CMP) circular muscle fibres. A nerve (N) and radial muscle fibres (R) are also visible in the micrograph. Compare A with Fig. 2A and note that juveniles have a much larger proportion of CMP to SMR circular muscle fibres. B and C show magnified views of the SMR and CMP cells, respectively. Scale bars in B and C are 10 µm. Bright-field microscopy of 1 µm glycol methacrylate sections stained with 1% Toluidine Blue.