ALO in the zebrafish. (A) Maximum intensity projection confocal micrograph of the red fluorescent surface of a 32-day-old zebrafish soaked in BODIPY 633. (B) Magnified image of the boxed area in panel A, with the ALO pseudocolored yellow. (C) Schematic diagram of the anatomical features shown in panel B. (D–F) Maximum intensity projection confocal micrographs of 9.3-mm (28 days post fertilization [dpf]) (D), 11.1-mm (34 dpf) (E), and 14.8-mm (34 dpf) (F) juvenile zebrafish soaked in BODIPY 633, showing stages prior to ALO emergence, initial ALO budding, and further ALO expansion, respectively. (G) Measurement of ALO length (µm) versus fish standard length (mm) (28 dpf, n = 6; 34 dpf, n = 8; 45 dpf, n = 3). ALOs emerge when fish reach ∼9–10 mm in body length. (H–K) Bright-field images of adult zebrafish ALO pre-amputation (H), immediately after amputation (I), 3 days after amputation (J), and 14 days after amputation (K), with yellow dashed lines and arrows marking the border of the ALO (regeneration, n = 6). (L–O) Images of ALOs found on other fish species, with yellow arrows noting the locations of the ALOs. Scale bars = 500 µm (A and H), 250 µm (B), 200 µm (D–F), 1 mm (L and M), and 2 mm (N and O).
