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Among squamate reptiles, snakes stand out for their diversity in photoreceptor morphotypes and pronounced differences in retinal architecture between diurnal and nocturnal species. Diurnal snakes have a cone-dominated retina, lacking typical rods, but containing a transmuted, cone-like rod and exhibiting a low photoreceptor density. Nocturnal species have rod-dominated retinas with high rod densities and two or three types of cones. Despite these striking differences, no previous study has examined inner-retinal neuron types or aspects of neural circuitry in snakes. In this study, we used immunohistochemistry to investigate a specific type of bipolar cell immunoreactive to the anti-protein kinase C alpha (PKC\u03b1) antibody, a well-established marker for rod bipolar cells, and to assess its connectivity with photoreceptors in eight nocturnal and 13 diurnal species of snakes from eight families. Nocturnal snakes exhibited a canonical rod-selective PKC\u03b1-immunoreactive rod bipolar cell, whereas in diurnal species, the anti-PKC\u03b1 antibody labeled a distinct population of long-wavelength-sensitive, cone-selective bipolar cells. This study reveals clear differences between diurnal and nocturnal species and highlights the remarkable plasticity and evolutionary innovation of the visual system in this group.<\/jats:p>","DOI":"10.1038\/s41598-026-47828-5","type":"journal-article","created":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T15:26:18Z","timestamp":1780500378000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Canonical PKC\u03b1-immunoreactive rod bipolar cells are present in nocturnal snakes but not in diurnal snakes"],"prefix":"10.1038","volume":"16","author":[{"given":"Einat","family":"Hauzman","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juliana H.","family":"Tashiro","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David J.","family":"Gower","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dora Fix","family":"Ventura","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pavel","family":"N\u011bmec","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kathleen F.","family":"Grego","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicholas R.","family":"Casewell","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Silke","family":"Haverkamp","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,6,3]]},"reference":[{"key":"47828_CR1","doi-asserted-by":"crossref","unstructured":"Walls, G. 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