Tackling the mysteries of earth's history and the evolution of life through planktonic foraminifera — Toward unraveling the complete picture of an invisible photosymbiotic network

Q1. What inspired you to become a researcher?

A1. Captivated by the grand world of "Phoenix"

From an early age, I had a vague interest in topics like Earth and the universe. In particular, I became fascinated with Osamu Tezuka's "Phoenix," and was captivated by its grand worldview where past and present intersect. In high school, I chose the science track because I wanted to study natural sciences, but I deliberately selected physics as my elective and studied biology on my own.

I chose to major in earth sciences with the goal of studying geology at university. When selecting a laboratory, I chose one specializing in paleontology and paleoenvironmental science where I could do fieldwork and work with living organisms. There, I encountered research on the fossils of "planktonic foraminifera," single-celled organisms that drift in the ocean, and I have been continuing research on this theme ever since. These organisms, which have calcium carbonate shells, are preserved as fossils in geological strata and can even be found in Cretaceous formations. During my master's program, I learned that foraminifera have an ecology called "photosymbiosis," which intrigued me. Photosymbiosis means harboring photosynthetic microalgae within their cells as symbionts. While traces of symbiosis can be explored even from fossils, I began working with living foraminifera to deepen my understanding of the phenomenon of photosymbiosis itself.

Q2. What research are you currently working on?

A2. The evolutionary history of photosymbiosis and identification of control genes

Many foraminifera harbor microalgae within their cells. Although both the host foraminifera and the symbiotic algae are unicellular organisms, they establish a photosymbiotic relationship in which the symbiotic algae provide organic matter produced through photosynthesis to the foraminifera, and the foraminifera provide metabolic products to the symbiotic algae.

As I advanced my research, I learned that it has been reported that radiolarians, a different type of plankton, also harbor the same algae as the symbiotic algae of foraminifera. I believe that different types of plankton are connected through symbiotic algae, forming an invisible network in the ocean, and I aim to unravel the complete picture of this network. Recently, I elucidated the evolutionary history of photosymbiosis in planktonic foraminifera and demonstrated that a robust partnership has been formed over a long evolutionary period.

Q3. A message for those aspiring to become researchers

A3. Don't limit your methods and continue to challenge yourself

There is a fateful episode that I still cannot forget. During my master's program, I had the opportunity to participate in a research cruise led by Dr. Richard Norris of Scripps Institution of Oceanography in the United States, whose paper I had read and been deeply impressed by at the time.

I had the opportunity to present my research on board, and when I told Dr. Norris, "I started this research after reading your paper," he was genuinely delighted that he had been able to inspire a young researcher. I would be happy if I could someday become a guiding presence for young researchers as well.

Photosymbiosis in foraminifera is a field with few researchers even on a worldwide level. The appeal is that many of the phenomena I discover become "world-first" findings. By valuing encounters, I was able to find a research subject I could become passionate about. I have not limited my research methods and have tried anything I thought necessary. Foraminifera are very beautiful, both as fossils and in their living form. I continue taking on my challenges today, captivated by the beauty of the small universe that unfolds beyond the microscope.

(Article: Yasuhiro Hatabe)