Photoparasitism as an Intermediate State in the Evolution of Apicomplexan Parasites
Abstract: 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.
Highlights:
- Apicomplexan parasites evolved from a phototrophic ancestor.
- Parasitism evolved multiple times in the Apicomplexa and in Apicomplexa-like protists.
- Chromerid algae are the closest known phototrophic relatives of parasitic Apicomplexa.
- The chromerid Chromera velia is a free-living alga that can infect coral larvae and live like a parasite.
Keywords: Apicomplexa; evolution; mixotrophy; parasitism; photoparasitism; phototrophy.
Oborník M. 2020: Photoparasitism as an Intermediate State in the Evolution of Apicomplexan Parasites. Trends in Parasitology 36: 727–734. [IF=5.560]
doi:10.1016/j.pt.2020.06.002
