Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Studies on the Motility of the Foraminifera. I. Ultrastructure of the Reticulopodial Network of Allogromia laticollaris (Arnold)

Jeffrey L. Travis and Robert Day Allen
The Journal of Cell Biology
Vol. 90, No. 1 (Jul., 1981), pp. 211-221
Stable URL: http://www.jstor.org/stable/1609389
Page Count: 11
  • More info
  • Cite this Item
Studies on the Motility of the Foraminifera. I. Ultrastructure of the Reticulopodial Network of Allogromia laticollaris (Arnold)
Preview not available

Abstract

Allogromia laticollaris, a benthic marine foraminifer, extends numerous trunk filopodia that repeatedly branch, anastomose, and fuse again to form the reticulopodial network (RPN), within which an incessant streaming of cytoplasmic particles occurs. The motion of the particles is saltatory and bidirectional, even in the thinnest filopodia detected by optical microscopy. Fibrils are visible by differential interference microscopy, and the RPN displays positive birefringence in polarized light. These fibrils remain intact after lysis and extraction of the RPN in solutions that stabilize microtubules (MTs). Electron micrographs of thin sections through these lysed and stabilized cytoskeletal models reveal bundles of MTs. The RPNs of living Allogromia may be preserved by standard EM fixatives only after acclimatization to calcium-free seawater, in which the streaming is normal. The MTs in the RPN are typically arranged in bundles that generally lie parallel to the long axis of the trunk and branch filopodia. Stereo electron micrographs of whole-mount, fixed, and critical-point-dried organisms show that the complex pattern of MT deployment reflects the pattern of particle motion in both flattened and highly branched portions of the RPN. Cytoplasmic particles, some of which have a fuzzy coat, are closely associated with, and preferentially oriented along, either single MTs or MT bundles. Thin filaments (∼5 nm) are also observed within the network, lying parallel to and interdigitating with the MTs, and in flattened terminal areas of the filopodia. These filaments do not bind skeletal muscle myosin S1 under conditions that heavily decorate actin filaments in controls (human blood platelets), and are ∼20% too thin to be identified ultrastructurally as F-actin.

Page Thumbnails

  • Thumbnail: Page 
211
    211
  • Thumbnail: Page 
212
    212
  • Thumbnail: Page 
213
    213
  • Thumbnail: Page 
214
    214
  • Thumbnail: Page 
215
    215
  • Thumbnail: Page 
216
    216
  • Thumbnail: Page 
217
    217
  • Thumbnail: Page 
218
    218
  • Thumbnail: Page 
219
    219
  • Thumbnail: Page 
220
    220
  • Thumbnail: Page 
221
    221