Premium
An enigmatic eye: the histology of the tuatara pineal complex
Author(s) -
Ung Casey YJ,
Molteno Anthony CB
Publication year - 2004
Publication title -
clinical and experimental ophthalmology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.3
H-Index - 74
eISSN - 1442-9071
pISSN - 1442-6404
DOI - 10.1111/j.1442-9071.2004.00912.x
Subject(s) - pineal gland , melatonin , biology , retina , histology , anatomy , endocrine system , pathology , medicine , neuroscience , endocrinology , hormone
Aim: To examine the histology of the tuatara pineal complex and to compare findings wtih those of Dendy. Some reptiles have an anatomically sophisticated pineal complex with a median pineal eye, a paraphysis and a pineal sac. In comparison, the human pineal gland is simple and homogenous and thought to be a phylogenetic relic. It is now considered a neuroendocrine gland the function of which is still not fully understood. Its simple anatomical structure is in contrast to its biochemical complexity; its secretions (the most studied being melatonin) modifying the function of the adeno‐ and neurohypophysis, thyroid and parathyroids, adrenal cortex and medulla, endocrine pancreas and the gonads. Methods: Histological sections of the brain of a neonatal tuatara were studied by light microscopy. Results: The histological findings of the pineal eye demonstrated a cornea‐like structure, rudimentary lens and simple retina. The adjacent paraphysis was a large, multisaccular organ and the pineal sac a very large saccular organ with a poorly differentiated retina. Conclusion: The pineal eye of the tuatara has a remarkably eye‐like structure with photoreceptors that in other reptiles have been shown to exhibit photoreceptive capabilities. The paraphysis appeared to have a secretory function that is as yet undetermined, while the pineal sac had the appearance of a poorly differentiated retina. Thus it appears that the complex biochemistry of the human pineal gland is reflected in the complex anatomical structure of this primitive reptile.