An Emerging System to Study Photosymbiosis, Brain Regeneration, Chronobiology, and Behavior: The Marine Acoel Symsagittifera roscoffensis

Abstract

The acoel worm Symsagittifera roscoffensis, an early offshoot of the Bilateria and the only well-studied marine acoel that lives in a photosymbiotic relationship, exhibits a centralized nervous system, brain regeneration, and a wide repertoire of complex behaviors such as circatidal rhythmicity, photo/geotaxis, and social interactions. While this animal can be collected by the thousands and is studied historically, significant progress is made over the last decade to develop it as an emerging marine model. The authors here present the feasibility of culturing it in the laboratory and describe the progress made on different areas, including genomic and tissue architectures, highlighting the associated challenges. In light of these developments, and on the ability to access abundant synchronized embryos, the authors put forward S. roscoffensis as a marine system to revisit questions in the areas of photosymbiosis, regeneration, chronobiology, and the study of complex behaviors from a molecular and evolutionary perspective.

A community perspective on the concept of marine holobionts: current status, challenges, and future directions

“…Controlled bi-or trilateral associations: Only a few models, covering a small part of the overall marine biodiversity, are currently being cultivated ex-situ and can be used in fully controlled experiments, where they can be cultured aposymbiotically. The flatworm Symsagittifera (= Convoluta) roscoffensis (Arboleda et al 2018), the sea anemone Exaiptasia (Baumgarten et al 2015;Wolfowicz et al 2016), the upside-down jellyfish Cassiopea (Ohdera et al 2018), and their respective intracellular green and dinoflagellate algae have, in addition to corals, become models for fundamental research on evolution of metazoan-algal photosymbiosis. In particular, Exaiptasia has been used to explore photobiology disruption and restoration of cnidarian symbioses (Lehnert et al 2012).…”

The digestive system of xenacoelomorphs

“…One specific case: the digestive system of S. roscoffensis Over the last few years, we have been analyzing different aspects of the morphology and development of the acoel Symsagittifera roscoffensis, another member of the family Convolutidae, which lives in the Atlantic coast of Europe (Arboleda et al 2018). As part of our study of the different tissue architectures, we generated a map of cell types within the hatchling by using the serial section TEM approach.…”

Better off alone? New insights in the symbiotic relationship between the flatworm Symsagittifera roscoffensis and the microalgae Tetraselmis convolutae

“…Among the most studied animal-algal relationships are the reef-building corals, hosting photosynthetic dinoflagellates in their polyps. More discreet and less known, the flatworm Symsagittifera roscoffensis (Graff 1891) establishes an obligatory symbiosis with the green alga Tetraselmis convolutae (Parke and Manton 1967;Arora 2016;Arboleda et al 2018). Their interaction is set up at each generation by worm juveniles ingesting microalgae which they will keep for the lifetime of the animal (Keebles 1910).…”