INTERMEDIATE FILAMENTS IN THE
CYTOSKELETONS OF FISH CHROMATOPHORES
DOUGLAS B. MURPHY* AND WILLIAM A. GRASSER
Department of Cell Biologv and Anatomv, Johns Hopkins Medical School, Baltimore,
Maryland 21205, U.SA. '
SUMMARY
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.