A cell of two halves
On Isonoura Beach, in the sands of Wakayama Prefecture, lives a microscopic flagellate with a double life. First observed in 2000 by biologists Noriko Okamoto and Isao Inouye, Hatena arenicola is a single-celled predator that can transform into a photosynthesizing, plant-like organism. This transformation is not its own doing; it occurs when the protist engulfs a specific type of green alga from the genus Nephroselmis.
Once the alga is captured, a strange remodeling begins. The predator, a colorless cell about 30-40 micrometers long, develops a complex feeding tube to hunt. After consuming a Nephroselmis cell, the protist loses this feeding apparatus. The captured alga also changes. It loses its own flagella and cytoskeleton, while its plastid—the photosynthetic part—swells to ten times its normal size, eventually occupying most of the host cell's interior. The alga's other internal components, like its mitochondria and Golgi body, are degraded. The host, now green and photosynthetic, uses the alga's red eyespot to guide its movement toward light, a behavior called phototaxis.