An eye for phytoplankton

The unicellular phytoplankton known as warnowiid dinoflagellates are a prime example of the remarkable diversity which exists in the realm of protsists. Within their single cell, these organisms have complex eyes or ‘ocelloids’, complete with structures resembling cornea, lens and retina. Gregory Gavelis et al. investigate the evolutionary origin of ocelloids using a single-organelle genomics approach in Erythropsidinium sp., Warnowia sp. and Nematodinium sp. isolates from marine waters off Japan and Canada. They find that ocelloids are built from pre-existing organelles of disparate origin. The cornea is derived from mitochondria, and the retinoid is made of an anastomosing network of plastids, originally derived from a secondary red-algal endosymbiont.