Haldar C, Bishnupuri K S
Pineal Research Laboratory, Department of Zoology, Banaras Hindu University, Varanasi-221 005, India.
Microsc Res Tech. 2001 Apr 1;53(1):25-32. doi: 10.1002/jemt.1065.
Although having a similar developmental pattern, the pineal gland of tropical birds varies in shape, size, and morphology, probably more than any other part of the avian brain. Following the old classification, we noted a solid follicular (transitional) type of the pineal gland in the nocturnal bird Athene brama, and a tubulo-follicular and elongated tubular types of pineal gland in diurnal birds Perdicula asiatica and Euroloncha punchulata, respectively. Detailed light (LM) and electron microscopic (EM) studies of the pineal gland from these tropical birds revealed the presence of a well-developed, functionally active gland in nocturnal birds (contrary to reports available until now). Unlike diurnal birds, the nocturnal bird A. brama has no deep pineal in the posterior region (near the habenular commissure). It could be that the deep encephalic receptors have no/fewer functions in nocturnal birds. At present, we were unable to define the significance of deep pineal in these tropical avian species. A notable difference in the proximodistal orientation of intrapineal follicles and parenchymatous cells was noted among these birds due to different habitats. Ultrastructurally, the pinealocytes exhibited great similarities in terms of secretory organelles, except for the presence of some peculiar membranous structure in E. punchulata. The pinealocytes have rudimentary photoreceptive features (e.g., outer segment) along with cytoplasmic organelles for secretory activity, suggesting both photosensory and photosecretory types of function. The present study also suggests more heterogenicity in pineal gland morphology (cellular architecture) among diurnal birds than the nocturnal one.
尽管具有相似的发育模式，但热带鸟类的松果体在形状、大小和形态上存在差异，可能比鸟类大脑的任何其他部分差异都要大。按照旧的分类方法，我们注意到夜行动物印度夜鹰的松果体为实心滤泡型（过渡型），而日行性鸟类灰胸竹鸡和栗头八色鸫的松果体分别为管状滤泡型和细长管状型。对这些热带鸟类松果体进行的详细光学显微镜（LM）和电子显微镜（EM）研究显示，夜行动物的松果体发育良好且功能活跃（与迄今为止的报道相反）。与日行性鸟类不同，夜行动物印度夜鹰在后部区域（靠近缰连合）没有深部松果体。可能是深部脑受体在夜行动物中功能缺失或较少。目前，我们无法确定这些热带鸟类物种中深部松果体的意义。由于栖息地不同，在这些鸟类中观察到松果体内滤泡和实质细胞的近端-远端方向存在显著差异。在超微结构上，除了栗头八色鸫中存在一些特殊的膜结构外，松果体细胞在分泌细胞器方面表现出很大的相似性。松果体细胞具有基本的光感受特征（如外段）以及用于分泌活动的细胞质细胞器，这表明其具有光感受和光分泌两种功能类型。本研究还表明，日行性鸟类松果体形态（细胞结构）的异质性比夜行动物更大。
