Praesagittifera naikaiensis is an acoelomorph worm native to the seashore of the Seto Inland Sea. P. naikaiensis harbors a species of prasinophytes, Tetraselmis sp., as a symbiont. The symbiotic algae are acquired horizontally from the environment during the larval stage. In this study, we established a method for the rearing of adult P. naikaiensis as a first step toward using the animal in the study of development, evolution, and the symbiotic mechanism. We kept the animals in aquaria with closed seawater circulations. The bottom of the aquarium was half covered with sand collected from the seashore of the Seto Inland Sea. An LED light was suspended over the aquarium to aid photosynthesis. The system was maintained at a salinity of 32–33 ppt and a temperature of 14°C, on a 14-h light (35–80 μmol quanta m−2s−1)/10-h dark photoperiod. We succeeded in constantly producing sexually mature animals, independent of season. The system developed here will serve as a foundation for future studies on acoel evolution and development.

本研究は科学研究費補助金(26924012)の助成を受けたものである。