Despite the benefits of phototrophy, many algae have lost photosynthesis and have converted back to heterotrophy. Parasitism is a heterotrophic strategy, with apicomplexans being among the most devastating parasites for humans. The presence of a nonphotosynthetic plastid in apicomplexan parasites suggests their phototrophic ancestry. The discovery of related phototrophic chromerids has unlocked the possibility to study the transition between phototrophy and parasitism in the Apicomplexa. The chromerid Chromera velia can live as an intracellular parasite in coral larvae as well as a free-living phototroph, combining phototrophy and parasitism in what I call photoparasitism. Since early-branching apicomplexans live extracellularly, their evolution from an intracellular symbiont is unlikely. In this opinion article I discuss possible evolutionary trajectories from an extracellular photoparasite to an obligatory apicomplexan parasite.

尽管有光养作用的好处，但许多藻类却失去了光合作用，并转变回异养作用。寄生是一种异养策略，apicomplexans是人类最具破坏力的寄生虫之一。apicomplexan寄生虫中存在非光合质体表明其光养祖先。相关的光养性chromeridus的发现为研究Apicomplexa中的光养与寄生之间的过渡打开了可能性。chromerid Chromera velia可以作为珊瑚幼虫中的细胞内寄生虫以及自由活动的光养生物生存，在我称之为光寄生病的情况下，光养与寄生关系结合在一起。由于早期分支的apicomplexans生活在细胞外，它们不可能从细胞内共生体进化。在这篇观点文章中，我讨论了从细胞外光寄生虫到强制性apicomplexan寄生虫的可能进化轨迹。