January 13, 2022
Keio University
Yu Funakoshi and Takumi Shito, second-year master's students at the Graduate School of Science and Technology, Keio University, along with Professor Kotaro Oka and Associate Professor Koji Hotta of the university's Faculty of Science and Technology, have defined the developmental stages of the European sea squirt (*Ascidiella aspersa*) and constructed a 3D embryo image resource as a first step toward establishing it as a new model organism for bioimaging research.
The European sea squirt is a species of tunicate belonging to the Urochordata, the closest relatives of vertebrates. This sea squirt is known as a harmful invasive alien species that reproduces invasively not only in Japan but around the world, causing damage to fisheries by attaching to cultured scallops. On the other hand, we have discovered that the embryos of this species are so transparent that they transmit 90% of visible light, and we are exploring its potential as a useful model organism for bioimaging research. However, until now, there has been no standard table of developmental stages, which is essential for developmental research on this species.
As the first step in establishing the European sea squirt as a model organism, this study defined 28 different developmental stages for it, from fertilized egg to hatched larva, by referencing the world-standard table of developmental stages for *Ciona intestinalis*. Furthermore, we have developed this table of developmental stages into a web-based 3D embryo image resource, making it accessible to anyone in the world. This resource contains over 3,000 tomographic and 3D images of European sea squirt embryos captured with a confocal laser scanning microscope.
The 3D image resource of the European sea squirt constructed in this study is essential for linking various omics data to each spatiotemporal hierarchy of the developmental stages and is expected to contribute to a systems-level understanding of embryonic development and phylogeny in chordates, including humans. Moreover, it is believed that advancing research on this species by developing its research infrastructure will lead to measures to prevent its attachment to scallop shells.
The research results were published online on December 17, 2021, in the Swiss scientific journal " Frontiers in Cell and Developmental Biology ".
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