Ultrastructural Changes in the Avian Brain Wulst during Captivity: A Transmission Electron Microscopy Study

Abstract

Stress presents challenges, and without adaptation, animals may develop severe psychological and physiological disorders regulated by neural networks manifesting in change of behavior and brain morphology. This study was undertaken to examine the subcellular ultrastructural changes in the avian forebrain's Wulst under acute and chronic captivity conditions, utilized transmission electron microscopy (TEM). The study involved avian species with high (crow and myna) and low (cattle egret) cognitive abilities. Birds were maintained in captivity in standard cages for 1 day and 7 days, representing acute and chronic captivity, respectively. In both phases of captivity there were many pathological changes in the Wulst, including cytoplasmic disorganization with vacuolization and electron-dense inclusions alongside increased lysosomal and autophagic activity, mitochondrial shape changes, swelling and loss of cristae, chromatin condensation, nuclear membrane irregularities; suggesting cellular degradation and impaired energy metabolism, and indicative of oxidative stress, protein aggregation, chromatolysis, necrosis and potential apoptotic processes. However, in acute captivity, all these changes were noted but with a lesser degree of occurrence than in chronic phase, indicating preserved neuronal integrity, and intact synaptic structures. There were variations of ultrastructural changes in avian forebrain's Wulst after captivity stress on the three bird species. The Crow’s Wulst was the less affected followed by Myna, while in the cattle egret there was a severe damage. These findings highlight the differential effects of captivity duration on cellular ultrastructure, with chronic stress leading to pronounced neuronal degeneration and alters the neural ultrastructure more robustly during the chronic captivity.