Pineal organ of the Muscovy duck

Abstract

Summary The avian pineal is a photosensory organ taking part in the organization of circadian and seasonal rhythms and playing an important role in the regulation of many behavior and physiological phenomena. The morphology of the pineal organ shows an enormous diversity. The aim of study was to investigate the histology and ultrastructure of the pineal organ in the Muscovy duck (Cairina moschata). The study was performed on 14-week-old females kept under natural lighting. The investigated pineals consisted of a wide distal part and narrow middle and proximal parts. The proximal part was attached to the diencephalon via the choroid plexus. The light microscopy showed a mixed structural form of the organ, which comprised both tubulo-follicular and solid parts. The stroma contained the lymphatic tissue, which occurred in a diffused form and as lymphoid nodules. Electron microscopy revealed the huge complexity of the parenchyma architecture, caused by the presence of several lumen-containing structures. According to their size and shape, they were classified into classical follicles, canals (diameter > 1 m) and canaliculi (diameter < 1 m). Pinealocytes were characterized by high variability of their shapes and sizes, frequently occurring partial or total reduction of the apical protrusions and presence of extremely numerous microtubules. The supporting cells constituted a prominent part of the pineal parenchyma and were represented by ependymal-like cells and astrocyte-like cells. Ependymal-like cells limited the lumen of follicles, canals and canaliculi.

Roles of Direct Photoreception and the Internal Circadian Oscillator in the Regulation of Melatonin Secretion in the Pineal Organ of the Domestic Turkey: A Novel In Vitro Clock and Calendar Model

“…This observation agrees with the results of ultrastructural studies showing that pinealocytes of the rudimentary receptor type are the predominant type of pinealocytes in the pineal organ of 12–14-week-old turkeys and that they share many similarities in organization with the photoreceptor cells of fish pineal organs, except for the presence of an outer segment [45]. The rudimentary receptor pinealocytes of turkeys are much better developed than those of chickens, geese, and Muscovy ducks [37,38,42,48].…”

“…Infrequent studies on other birds have shown that the functional significance of the direct and indirect routes of the effect of light on pineal organ activity as well as the contribution of each clock in the regulation of MLT secretion differ significantly between avian species [2,6,9,15]. These differences are not be surprising because the avian pineal organs show among the greatest variability of morphology observed among vertebrates [37,38,39,40,41,42,43,44,45,46,47,48]. Concerning poultry species, our in vitro studies on the pineal organs of Anseriformes birds demonstrated that light acting directly on pinealocytes is not able to ensure the precise entrainment of MLT secretion to a light-dark cycle and that norepinephrine is the main factor controlling pineal organ activity in the duck and the goose [7,25].…”

Effects of different light intensities on the transcriptome changes of duck retina and pineal gland

“…The pineal gland is dominated by synaptic pathways originating in the SCN of the hypothalamus ( Simonneaux and Ribelayga, 2003 ). The pineal gland is a photosensitive organ, which participates in circadian and seasonal rhythms, and plays a vital role in regulating many behavioral and physiological phenomena ( Kwiecińska et al, 2017 ).…”