牙鲆脑垂体早期发育的组织学观察

Histological observation on early development of pituitary in flounder Paralichthys olivaceus

垂体作为鱼类最重要的内分泌器官之一,在生长、发育、生殖以及其他一些内分泌相关生理活动中起重要作用。作者采用组织学方法观察了牙鲆的脑垂体发生,对不同发育时期的腺垂体细胞进行了初步鉴定。结果表明,孵化后1d仔鱼的间脑下方可见一实心细胞团,于孵化后3d迁移至间脑后方的漏斗体下,与来自漏斗体的神经内分泌细胞及其神经纤维结合共同形成脑垂体,前者形成腺垂体,后者则主要形成神经垂体。孵化后8d腺垂体分为中间部(Pars intermedia,PI)和外侧部(Pars distalis,PD)两部分。孵化后14d腺垂体分化为前外侧部(Rostral pars distalis,RPD)、中外侧部(Proximal pars distalis,PPD)和PI共3部分,为"前后型"脑垂体。稚鱼变态期间及变态完成后的幼鱼,各部分从"前后型"排列开始向"背腹型"排列转变。孵化后14d的牙鲆仔鱼中,PPD细胞多呈强嗜酸性,至变态完成后一直是PPD的主要细胞;PI靠近神经纤维的细胞呈强嗜碱性。孵化后42d的牙鲆幼鱼RPD中,与神经垂体相邻的少量细胞呈嗜碱性,而其下方细胞则呈嗜酸性。根据成体牙鲆激素分泌细胞的染色特征对上述各细胞类型进行了推测。

The fish pituitary, as an important endocrine organ, plays vital roles in endocrine-related function including growth, development and reproduction. In the present study, the histological development of pituitary was observed for flounder Paralichthys olivaceus, and adenohypophysial cells were identified preliminarily. The results showed that a solid cell cluster was located under the diencephalon in 1 day post hatching （DPH） fry, migrated towards under the infundibulum at the posterior dieneephalon, and coalesced with neuroendocrine cells and nerve fibers from the infundibulum to form the pituitary preliminarily in 3 DPH fry. The cell cluster formed the adenohypophysis, and others primarily formed the neurohypophysis. In 8 DPH fry, the adenohypophysis differentiated into two portions： the pars intermedia （PI） and the pars distalis （PD）, which was divided into the rostral pars distalis （RPD） and the proximal pars distalis （PPD） in 14 DPH fry. The fore-and-aft pituitary changed to dorsal-ventral position during metamorphosis stages of juvenile to young fish. The highly acidophilic cells were found to dominate in the PPD in the 14 DPH fry and posterior developmental stages, and cells close to nerve fibers in the PI showed strong basophilia. In the 42 DPH young fish, a few cells around nerve fibers in the RPD were basophilic, whereas cells in the lower part of RPD were acidophilic. The types of these cells were speculated based on the staining characteristics of hormone-secreting cells in the adult P. olivaceus.