Fig. 1. Swimming tadpole does not shown features of apoptosis. (A) Swimming tadpole of Ciona intestinalis was labeled with TUNEL. Digitized images were merged to superimpose the TUNEL labeling (green pseudocolor field) over the respective Nomarski field. No sign of apoptosis was observed at this stage (Ot, otolith; Oc, ocellus; N, notochord). Double arrowed line indicates the level of the ultra-thin section shown in B. (B) Electron micrograph of cross-section of a Ciona tadpole tail at 20 hours post fertilization (hpf) (T, tunic; EP, epidermis; SM, striated muscle cell; NT, neural tube; ES, endodermal strand; NC, notochord). (C) Cross-section of a striated muscle cell from the tail of a Ciona intestinalis tadpole. The myofibrils (My) seen in the cross section are arranged in a single peripheral layer. The nucleus (N) and mitochondria (m) are present in the internal core. (D) Striated muscle cell tangentially sectioned and showing one sarcomere. Scale bars: 380 µm in A; 7 µm in B; 3 µm in C; 0.4 µm in D.