Diurnal changes of lysosome-related bodies in the crayfish photoreceptor cells

Summary

The effect of illumination on the degradation of microvillar membrane in the invertebrate photoreceptor cell has been correlated with the appearance in the cytoplasm of certain distinct lysosome-related bodies. Three types of organelles were distinguished in the retinula cell cytoplasm of the crayfish, multivesicular bodies (MVB), both large (4.20-1.50 μm) and small (1.49-0.30 μm), combination bodies (CB), and lamellar bodies (LB). Under diurnal lighting conditions significant temporal differences were found in the appearance of these three classes of organelles in the retinula cell. Small MVB are present at a consistent level throughout most of the diurnal cycle but show peak numbers at 30 min after light onset and again after 6 h of dark adaptation. Large MVB increase significantly 1 h after light onset and remain elevated through 4 h in the light. After 4 h the large MVB decline gradually for the remaining light period. Combination bodies and LB do not begin to increase until 1 h after light onset and are at peak levels between 4 and 6 h into the light period. The minimum rhabdome diameter coincides with the peak levels of large MVB, CB, and LB. These data support the hypothesis that light causes microvillar membrane breakdown, resulting in the initial production of MVB which in turn undergo degradation to form CB and finally LB. This primary degradative response appears to be completed within the first 8 h of the light period.