Ocelloid
![A light micrograph of an ocelloid-containing dinoflagellate. The nucleus is marked n, the ocelloid is indicated with a double arrowhead, and a posterior cell extension is indicated with an arrow; scale bar = 10 µm.[1]](/Images/godic/202501/30/Bmc_evol_bio_hoppenrath_proterythropsis_ocelloid_fig1a2852.png")
![A micrograph of a single ocelloid; scale bar = 5 µm.[1]](/Images/godic/202501/30/Bmc_evol_bio_hoppenrath_proterythropsis_ocelloid_fig1e2853.png")
![A negative staining transmission electron micrograph of an ocelloid (white box), indicating the hyalosome (H) and retinal body (R), as well as a portion of the piston (Ps). Scale bar = 10 µm.[5]](/Images/godic/202501/30/Plos_one_hayakawa_erythropsidinium_ocelloid_EM_fig1b2853.png")
![Comparison between the structures of the ocelloid (1) and the vertebrate eye (2). Components are indicated as the hyalosome (H), retinal body/retina (R), and crystallin lens (C).[5]](/Images/godic/202501/30/Plos_one_hayakawa_erythropsidinium_ocelloid_EM_figS12853.png")
An ocelloid is a subcellular structure found in the family Warnowiaceae (warnowiids), which are a members of a group of unicellular organisms known as dinoflagellates. The ocelloid is analogous in structure and function to the eyes of multicellular organisms, which focus, process and detect light. The ocelloid is much more complex than the eyespot, a light-sensitive structure also found in unicellular organisms, and is in fact one of the most complex known subcellular structures. It has been described as a striking example of convergent evolution.