Retinal neuroanatomy of two emerging model organisms, the spiny mouse (Acomys dimidiatus) and the Mongolian gerbil (Meriones unguiculatus)

Purpose: Degenerative eye diseases such as macular degeneration and retinitis pigmentosa slowly deteriorate vision, ultimately leading to blindness. Current research with laboratory animal models largely utilizes small mammals that are nocturnal and lack the ability to restore lost vision. In contrast, the Mongolian gerbil is a diurnal rodent with good photopic vision, and the eastern spiny mouse is a small desert-dwelling rodent with remarkable regenerative capabilities. The goal of this study was to identify several antibodies that detect retinal cell classes in Meriones and Acomys , and to describe the retinal anatomy of these two species in comparison to outbred laboratory mice ( Mus musculus ). Methods: Retinal sections were obtained from adult eyes and subjected to histological or immuno-staining with antibodies for various retinal cell types. Sections were imaged by light, fluorescence, and confocal microscopy, assessing cell number and morphology. Cell density, morphology, and placement were compared between species qualitatively and quantitatively. Results: Immunohistochemical visualization and analysis of all general classes of retinal neurons and Müller glia revealed a classic assembly of retinal cells with a few deviations compared to Mus . Meriones displayed the highest density of cone photoreceptors and Acomys the lowest. A higher density of bipolar cell bodies in the proximal portion of the inner nuclear layer was observed in both Acomys and Meriones compared to Mus , and both species exhibited an increase in amacrine cell density compared to Mus . Conclusion: We have characterized similarities and differences in the retinal anatomy and cellular density between Meriones , Acomys , and Mus . We identified several commercially available antibodies that reliably detect retinal cell types in the Acomys and Meriones retina. Our results provide a foundation for future research into the visual system adaptations of both of these interesting rodent species. ### Competing Interest Statement The authors have declared no competing interest.