The highly developed symbiotic system between the solar-powered nudibranch Pteraeolidia semperi and Symbiodiniacean algae

Abstract

The intricate coexistence of Symbiodiniacean algae with a diverse range of marine invertebrates underpins the flourishing biodiversity observed within coral reef ecosystems. However, the phenomenon of coral bleaching--precipitated by the dissolution of symbiotic relationships with Symbiodiniaceae--poses a significant threat to these ecosystems, thereby necessitating an urgent investigation into the underlying symbiotic mechanisms. The symbiosis between nudibranchs and Symbiodiniaceae has been identified as an efficacious model for examining these mechanisms, yet a comprehensive understanding of their histological structures and cellular processes remains elusive. In this study, we concentrate on the nudibranch host Pteraeolidia semperi, renowned for its exceptional symbiotic capabilities, and we elucidate its sophisticated symbiotic architecture. Furthermore, we delineate the bleaching process within the nudibranch, uncovering the associated cellular processes. Collectively, these findings furnish invaluable insights into the intricate relationship between nudibranchs and Symbiodiniaceae, thereby contributing to our understanding of the symbiosis that sustains these critical marine ecosystems.