Cell Tiss. Res. 164, 473-480 (1975) - 9 by Springer-Verlag 1975 Subsurface Cisterns in the Vertebrate Retina* Steven K. Fisher** and Karen Goldman Department of Biological Sciences, University of California at Santa Barbara, Santa Barbara, California, U.S.A. Summary. Structures identified as subsurface cisterns (SSC's) were found in retinal neurons and their processes in the Western grey squirrel, the California and 13-line ground squirrels, the South African clawed toad, and the domestic cat. The SSC's are located in amacrine, bipolar, and gan- glion cells; they are connected with the rough endoplasmic reticulum and are associated with specific membrane specializations. SSC's were not seen in the MOiler cells, an observation which agrees with earlier reports that these organelles do not exist in glial cells. Key words: Subsurface cisterns - Retina - Endoplasmic reticulum - Neurons - Membrane specialization. Introduction Subsurface cisterns (SSC's) are generally considered to be distinct organelles, unique to neurons and not occurring in glial cells (Rosenbluth, 1962; Sieges- mund, 1968 ; Weis, 1968; Pannese, 1968; Raviola and Raviola, 1969; Takahashi and Wood, 1970; LeBeux, 1972). There is, however, no known function for these unusual structures. Most authors speculate on the role of SSC's in terms of possible alteration of neuronal membrane functions, but there is no physiolog- ical or biochemical evidence for such a role. Recent findings reported by LeBeux (1972) and by us in the present paper, show that there are specific modifications of cell membranes at the site of the SSC's themselves which seem to indicate some specific role in neuronal function. Send offprint requests to: Dr. Steven K. Fisher, Department of Biological Sciences, University of California at Santa Barbara, Santa Barbara, California 93106, USA. * Supported by Grant EY 00888 from the USPHS to S.K. Fisher. ** The authors wish to thank Dr. Katherine Esau for the use of her electron microscope facilities, Professor B.B. Boycott for his critical reading of the manuscript, and Mr. Kenneth Linberg for technical assistance.