SEDLMAYR, J; REHOREK, S; LEGENZOFF, E; SANJUR, J; Univ. of Ca., Los Angeles; Slippery Rock Univ.; Slippery Rock Univ.; Slippery Rock Univ.: Circadian Endocrinological Network in Archosauria
The Amniote Head Project is devoted to the examination of various cephalic structures and systems within the framework of a comparative study of basal and highly derived taxa across several amniote clades. Specimens are studied at multiple levels, ranging from embryological development through to physiology. The testing and determination of homologous structures, reconstruction of the ancestral amniote head “bauplan”, and documentation of evolutionary derivations from this bauplan are key aspects of this research. Numerous techniques will be employed, including gross anatomical observation, serial histological sectioning, radioimmunoassays, clearing and staining, micro-CT and immunocytochemistry. The results of this project focus on the Harderian-pineal-retinal-hypothalamic axis (HaH) and its relation to circadian rhythms (cyclical behavioral patterns regulated by indoles) in avesuchian archosaurs and other amniotes. The precise structure of the components of the HaH axis, including their vascular and nervous supply, was examined. The avian and crocodilian retina, Harderian and “pineal/parapineal” glands are highly vascular structures. The crocodilian Harderian gland has structural similarities to the squamate gland, including mucous secreting cells. However, as in birds, the crocodilian Harderian gland possesses plasma cells and lipid secreting cells. Additional issues include: (1) presence of a functional pineal gland in crocodilians; (2) anatomy and histochemistry of the Harderian and pineal glands in basal birds (ratites and tinamous); (3) comparison of Harderian glands and the biological significance of the secretions in extant avesuchians, including the lack or presence of melatonin in the gland and the retina; and (4) a synthesis of relations and functions between the various components of the circadian endocrinological network.
