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Cytoarchitecture of the optic tectum of the squirrelfish, Holocentrus
Author(s) -
Schroeder Dolores M.,
Vanegas Horacio,
Ebbesson Sven O. E.
Publication year - 1980
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901910303
Subject(s) - tectum , biology , axon , neuropil , cytoarchitecture , nissl body , stratum , anatomy , neuroscience , central nervous system , midbrain , paleontology , staining , genetics
Abstract The Holocentrus has large eyes and a well‐developed optic tectum. Nissl and fibers stains and various Golgi techniques show that the optic tectum of Holocentrus has six strata which can be subdivided into 14 alternative cell and fiber layers, some of which have additional organization. The stratum marginale (SM) is especially impressive in this fish and contains dendrites of pyramidal neurons, marginal fibers from torus longitudinalis, and axon‐like processes (the SM ascending axons) from cell located in the stratum griseum centrale (SGC). Stratum opticum (SO) and stratum fibrosum et griseum superficiale (SFGS) have many small neurons with limited dendritic fields. The large, so‐called pyramidal cell of SFGS has an extensive dendritic tree in SM and descending dendrites and axon to SGC. The latter has a variety of neurons with large dendritic fields in various layers of the tectum; the most distinctive, however, is the large fusiform neuron with its shepherd's crook axon. This stratum also has a dense layer of neuropil, the internal plexiform layer. Stratum album centrale (SAC) is primarily a fibrous layer, and stratum periventriculare (SPV) is a dense cellular area with the upper portion containing neuronal types also found in SGC and different from the typical neurons found in SPV. The latter have a major ascending branch with various dendritic patterns, and often do not have an identifiable axon; however, some of these cells have extensive branches throughout SFGS with an axon‐like appearace. Some general conclusions were made about the functional significance of the various tectal layers and cell types.