Pleodorina starrii is a species of algae that resides in freshwater in Japan.[1]
It is trioecious meaning males, females, and hermaphrodites exist in the species.[2]
Reproduction is asexual under normal conditions and creates colonies of clones with the same genotype.[3][4] Sexual reproduction is induced by low-nitrogen conditions and is anisogamous.[1]
The species was involved in a 2006 study that provided the first molecular genetic evidence for the evolutionary link between sexes and mating types.[5][6]: 215–216, 222 A male-specific gene was founded in the species and named "Otokogi", meaning manliness or chivalry in Japanese.[6]: 221
The species was previously believed to be heterothallic with males and females, but a 2021 study revealed it also contained hermaphrodites.[7] This study was the first time the sexual system trioecy has been reported in haploid species and it challenged models for the evolution of sexual systems.[2]