An enigmatic eye: the histology of the tuatara pineal complex
Article first published online: 2 DEC 2004
Clinical & Experimental Ophthalmology
Volume 32, Issue 6, pages 614–618, December 2004
How to Cite
Ung, C. Y.-J. and Molteno, A. C. (2004), An enigmatic eye: the histology of the tuatara pineal complex. Clinical & Experimental Ophthalmology, 32: 614–618. doi: 10.1111/j.1442-9071.2004.00912.x
- Issue published online: 2 DEC 2004
- Article first published online: 2 DEC 2004
- pineal complex;
- pineal gland;
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.