The highly developed symbiotic system between the solar-powered nudibranch Pteraeolidia semperi and Symbiodiniacean algae
Hideaki Mizobata,
Kenji Tomita,
Ryo Yonezawa,
Kentaro Hayashi,
Shigeharu Kinoshita,
Kazutoshi Yoshitake,
Shuichi Asakawa
Affiliations
Hideaki Mizobata
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan; Corresponding author
Kenji Tomita
Technology Advancement Center, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
Ryo Yonezawa
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
Kentaro Hayashi
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
Shigeharu Kinoshita
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
Kazutoshi Yoshitake
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
Shuichi Asakawa
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan; Corresponding author
Summary: The intricate coexistence of Symbiodiniacean algae with a diverse range of marine invertebrates underpins the flourishing biodiversity observed within coral reef ecosystems. However, the breakdown of Symbiodiniaceae–host symbiosis endangers these ecosystems, necessitating urgent study of the symbiotic mechanisms. The symbiosis between nudibranchs and Symbiodiniaceae has been identified as an efficacious model for examining these mechanisms, yet a comprehensive understanding of their histological structures and cellular processes remains elusive. A meticulous histological exploration of the nudibranch Pteraeolidia semperi, employing optical, fluorescence, and electron microscopy, has revealed fine tubules extending to the body surface, with associated epithelial cells having been shown to adeptly encapsulate Symbiodiniaceae intracellularly. By tracing the stages of the “bleaching” in nudibranchs, it was inferred that algal cells, translocated via the digestive gland, are directly phagocytosed and expelled by these epithelial cells. Collectively, these insights contribute substantially to the scholarly discourse on critical marine symbiotic associations.
