Intermediate filaments in the cytoskeletons of fish chromatophores.

When fish pigment cells (melanophores, erythrophores) are lysed by a modified Kleinschmidt method on a buffer-air interface and examined by electron microscopy, large numbers of intermediate filaments are observed. The intermediate filament networks are distinct from actin and tubulin, and entrap the pigment as determined by stereo viewing of freeze-dried rotary-shadowed specimens. During lysis, under conditions that do not preserve actin filaments or microtubules, the area covered by dispersed pigment granules reaches a maximum size and remains stable for many minutes, suggesting that intermediate filaments are responsible for holding the pigment in position and preventing further cytoplasmic dispersion. These observations demonstrate that fish pigment cells contain large numbers of intermediate filaments and suggest that they may be important for coordinating pigment granule movement.