Transmission of a heterologous clade CSymbiodiniumin a model anemone infection system via asexual reproduction

Abstract

Anemones of genusExaiptasiaare used as model organisms for the study of cnidarian-dinoflagellate (genusSymbiodinium) endosymbiosis. However, while most reef-building corals harborSymbiodiniumof clade C,Exaiptasiaspp. anemones mainly harbor clade BSymbiodinium(ITS2 type B1) populations. In this study, we reveal for the first time that bleachedExaiptasia pallidaanemones can establish a symbiotic relationship with a clade CSymbiodinium(ITS2 type C1). We further found that anemones can transmit the exogenously supplied clade CSymbiodiniumcells to their offspring by asexual reproduction (pedal laceration). In order to corroborate the establishment of stable symbiosis, we used microscopic techniques and genetic analyses to examine several generations of anemones, and the results of these endeavors confirmed the sustainability of the system. These findings provide a framework for understanding the differences in infection dynamics between homologous and heterologous dinoflagellate types using a model anemone infection system.