Organization of diencephalon of the sturgeons. Preoptic area

Cytoarchitectonics of preoptic area of diencephalon of chondroid ganoid fish (the sturgeons) was studied in serial sections using Nissl and Bilschowski techniques, the latter in Viktorov’s modification). The preoptic area of the hausen, Huso huso L., Kura sturgeon, Acipenser guldenstaedtii persicus n. kurensis Belyaeff, Caspian sturgeon, Acipenser stellatus Pall. and the sturgeon Acipenser nudioventris Lov. was shown to be one of the largest parts of diencephalon. It is located along the rostral excess of the third ventricle and the anterior third of the ventricle thalamic part. Eight nuclei are identified in the preoptic area: (1) anterior microcellular preoptic nucleus, (2) suprachiasmatic nucleus, (3) accessory preoptic nucleus, (4) intrachiasmatic nucleus, (5) magnocellular preoptic nucleus, (6) posterior microcellular preoptic nucleus, (7) caudal preoptic nucleus, (8) entopeduncular nucleus. Besides, microcellular, magnocellular, and gigantocellular parts are identified in the magnocellular preoptic nucleus. The obtained results indicate high differentiation of this area of the sturgeons among Actinopterygii.