Studies On The Origin And Development Of The Pituitary Gland And Its Ultrastructure Of Teleost, Silurus Asotus

The process of the origin and development of the pituitary gland and it' s ultrastructure of Silurus asotus have been observed using laser scanning confocal microscopy technology and transmission electron microscpe (TEM). It' s shown from the results that the pituitary gland of Silurus asotus originates from two embryonic cells of different position; and the doral wall of the original cavum oris forms the rostral pars distali (RPD) and the proximal pars distalis (PPD); the infundibulum of the ventral part of diencephalons forms the the pars intermedia (PI) and the neurohypophsis.In a 3-day old larva, the pituitary gland is formed and is of front-back style. In a 5-day old larva, Neurohypophsis and Adenohypophysis can be distinguished. We can also make out the RPD, the PPD and PI. At this time, the growth hormone (GH) cells in the PPD have differentiated. Except for the GH cells in the PPD, no other hormone cells were found differentiated. Anteriorticrticotrophic (ACTH) cell and Prolactin (PRL) cell in RPD do not differentiate until the larva got 15-day old. Blood capillary begins to spread inside the pituitary gland. In a 20-day old larva, all harmone cells in the pituitary have differentiated.Pituitary gland is of front-back style before 11-day old. Thearrangement of the RPD, PPD and PI appear vertically in 15-day and 20-day old larvas. Pituitary gland is of dorsoventral style in Silurus asotus of sexual maturity.The pituitary gland of Silurus asotus has no median hump and vein system that can be found in other vertebrates. Each type of hormone secretory cells is adjusted directly by the nerve fibre in the pituitary. The nerve secretory fibre can be divided into types of A1, A2 and B. The nerve fibre forms synaptic or indirect links with special harmone secretory cells.Seven types of hormone secretory cells are found in the Adenohypophysis of Silurus asotus of sexual maturity, named as anteriorticrticotrophic (ACTH) cell, prolactin (PRL) cell, growth hormone (GH) cell, thyrotrophs (TSH) cell, gonadotropin hormone (GTH) cell, melanophore-stimulating hormone (MSH) cell and PAS-cell. The characteristic of their ultrastructure is the same as other scholars found in other bony fish. Only one type of GTH cells is observed in the pituitary of sexual mature Silurus asotus.