Rod photoreceptors in the adult teleost retina are produced by rod precursors located in the outer nuclear layer (ONL). Annual fishes of the genus Austrolebias exhibit extensive adult retinal cell proliferation and neurogenesis, as well as surprising adaptive strategies to their extreme and changing environment, including adult retinal plasticity. Thus, here we identify and characterize rod precursors in the ONL of the Austrolebias charrua retina. For this aim we used classical histological techniques, transmission electron microscopy, detection of cell proliferation, and immunohistochemistry. Through these complementary approaches, we describe a cell population clearly distinguishable from photoreceptors in the ONL of the adult retina of A. charrua, which we propose corresponds to the rod precursor population. These cells exhibited particular morphological and ultrastructural characteristics, uptake of cell proliferation markers (BrdU+) and expression of stem cell markers (Sox2+). Determining the existence of the population of rod precursors is crucial to understand the sequence of events related to retinal plasticity and regeneration.
Keywords: Annual fish; Histology; Retina; Rod precursor; Ultrastructure.
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