Morphology of the adrenal homologues in two hillstream teleostean fishes from India.

In Garra gotyla and Pseudecheneis sulcatus, the interrenal and chromaffin tissues represent homologues of the adrenal cortex and medulla, respectively, and are confined to the largely lymphoid head kidneys in a bilaterally symmetrical topographical pattern. Together they form a collar round the postcardinal vein, with a thickness of 300 microns in Garra gotyla and 150 microns in Pseudecheneis sulcatus. Distributionally, the interrenal tissue conforms to Nandi's type III and type I and the chromaffin tissue to type V and type III in Garra gotyla and Pseudecheneis sulcatus, respectively. The interrenal cells in these species are polygonal, cuboidal or columnar, and are filled with coarse basophilic cytoplasm. The chromaffin cells form syncytial patches and have sparsely granular cytoplasm.