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Transmission electron micrograph of unstained cryo-section of a sperm cell of the starfish Patiria miniata. Echinoderm sperm nuclei are unusual in that chromatin fibers are clearly seen, allowing their diameter to be accurately determined. Cryosections of frozen material are typically of low contrast and show defects such as knife marks and compression. Despite these defects, individual chromatin fibers are clearly visible.

Technical Details

Whole sperm from the starfish P. miniata were cryo-fixed by plunging into liquid ethane, thin cryosections prepared, and examined in the frozen hydrated state using a Philips CM12 TEM operated at 80KV. Low dose images were recorded on SO-163 film. See also: Woodcock CL 1994 Chromatin fibers observed in situ in frozen hydrated sections. Native fiber diameter is not correlated with nucleosome repeat length. J Cell Biol 125:11-9.

Biological Sources

NCBI Organism Classification
Patiria miniata
Cell Type
Cellular Component
male germ cell nucleus

Biological Context

Biological Process
nucleus organization
chromatin organization


Chris Woodcock


This image is representative of a group of similar images.


Image Type
recorded image
Imaging Mode
transmission electron microscopy (TEM)
Parameters Imaged
electron density
Source of Contrast
intrinsic mass distribution
defocus phase contrast
Visualization Methods
visualization of contiguous regions
Processing History
unprocessed raw data

Sample Preparation

unfixed tissue
cryofixed tissue
Relation To Intact Cell
microtome-sectioned tissue


Spatial Axis Image Size Pixel Size
X 3211px 0.71nm
Y 2188px 0.71nm
*CIL – Cell Image Library accession number. Please use this to reference an image.