Glial cells: basic components of clusters of supramedullary neurons in pufferfish

In this paper a cytochemical and ultrastructural study of clustered supramedullary neurons (SN) of Tetraodon fluviatilis (Tetraodontiformes) is presented. SN are large-sized nerve cells that have a high metabolic rate and are intensely engaged in protein biosynthesis. The SN are completely surrounded by two types of glial cell, which have been ultrastructurally, histochemically and immunohistochemically identified as astrocyte-like cells and microglial cells. The glial cells are located very close to the SN and sometimes contact them, which suggests that they do not only provide mechanical support but are also trophic for the SN and serve their functioning. We consider these glial cells as a constitutive and functional part of the cluster of SN, and therefore propose that the SN cluster constitute a suitable model to study in detail the morphological and functional relationships between neurons and glial cells in Anamnia.