Green algae
Pelagic phototaxis is present in green algae – it is not present in glaucophyte algae or red algae. Green algae have a "stigma" located in the outermost portion of the chloroplast, directly underneath the two chloroplast membranes. The stigma is made of tens to several hundreds of lipid globules, which often form hexagonal arrays and can be arranged in one or more rows. The lipid globules contain a complex mixture of carotenoid pigments, which provide the screening function and the orange-red colour, as well as proteins that stabilize the globules. The stigma is located laterally, in a fixed plane relative to the cilia, but not directly adjacent to the basal bodies. The fixed position is ensured by the attachment of the chloroplast to one of the ciliary roots. The pigmented stigma is not to be confused with the photoreceptor. The stigma only provides directional shading for the adjacent membrane-inserted photoreceptors (the term "eyespot" is therefore misleading). Stigmata can also reflect and focus light like a concave mirror, thereby enhancing sensitivity.