Nile red can stain adipose tissues in living medaka.

(A) Medaka larva at 15 days post-hatch (dph) stained with Nile red. (B) Medaka larva at 15 dph stained with Oil red O. Nile red stained the same parts of the larvae as Oil red O. These included under the eyes (arrows), at the base of the pectoral fin (black arrowhead), along the dorsal wall of the abdominal cavity, and around the sides of the anus (compare A and B, white arrowhead). Scale bar = 1 mm. (C and D) Adult female medaka was stained with Nile red. (C) Stereomicroscopic image. (D) Fluorescent stereomicroscopic image. The dashed circle area indicates adipose tissues in panel C. adp, adipose tissue; dt, digestive tract; lv, liver; ov, ovary; sp, spleen. Fluorescence signals were observed in visceral adipose tissues (D, arrows). Scale bar = 1 mm. (E and F) Magnified images of the boxed area in panel D. (E) Stereomicroscopic image. (F) Fluorescent stereomicroscopic image. Fluorescence signals were apparent in many adipocytes. Scale bar = 200 μm.