The nudibranch Berghia stephanieae (Valdés, 2005) is not able to initiate a functional symbiosome-like environment to maintain Breviolum minutum (J.E.Parkinson & LaJeunesse 2018)

Photosymbiosis is found in different animal lineages and best understood cnidarians. A successful initiation maintenance of the symbiosis between hosts photosymbiotic partners based on a recognition by specific host receptors. This triggers signaling cascades that promote photobiont tolerance host, including an interpartner nutrient exchange ability to cope with increased levels reactive oxygen species (ROS) generated photobiont. Key inhibition phagosomal maturation resulting formation symbiosome. In animals other than cnidarians, little known about photosymbiosis maintenance, for instance sea slugs belonging Nudibranchia. Here, we investigated gene expression profile Berghia stephanieae , which able incorporate Breviolum minutum from its cnidarian prey Exaiptasia diaphana (Rapp, 1829) but not maintain algae more couple days during starvation. We show similar mechanisms present identified some additional candidate genes might be molluscan recognition. Downstream, B. responds ROS stop or decrease immune response against seem key factors missing accounts unstable this slug. Hence, can considered transitional state toward stable help elucidate general aspects evolutionary processes involved establishing photosymbioses animals.