Photosymbioses under stress: photoinhibition and phototaxis in the sea anemone Exaiptasia diaphana

• Autor(a) principal: Silva, Patricia Carvalho da
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/39241
• topic: Sea anemones; Exaiptasia; Photoacclimation; Photoinhibition; Photoprotection; Phototaxis; Contraction

Marine cnidarians (e.g., sea anemones and corals) and dinoflagellate algae of the Symbiodineaceae familiy can coexist harmoniously in symbiotic associations. This study aimed to study the photophysiology and photobehavior of individuals of the sea anemone Exaiptasia diaphana harboring symbiodineaceaen endosymbionts. The photoacclimation state of the anemones was characterized non-destructively using in vivo imaging of chlorophyll fluorescence to generate light-response curves of the relative electron transport rate (rETR) of photosystem II (PSII). Photoinhibition under high light was studied by measuring the constant rates of PSII photoinactivation (kPI) and repair (kREC), using lincomycin as an inhibitor of protein synthesis. Exposure to high light caused the contraction of the anemones, which was quantified using the images of chlorophyll fluorescence. The photophysiological light preferences were compared with the photobehavior of the anemones along a light gradient. The light-saturated photosynthetic activity (rETRm) reached values of 184.4 ± 51.1 and the photoacclimation parameter Ek attained 314.8 ± 94.8 μmol quanta mˉ² sˉ¹. The optimal light intensity, Eopt, reached 729.5 ± 296.4 μmol quanta mˉ² sˉ¹. kREC was in all cases higher than kPI (1.55×10ˉ⁴ sˉ¹ and 6.26×10ˉ⁵ sˉ¹, respectively), indicating that PSII repair ability was considerably greater than susceptibility to photoinactivation damage. The anemones not subjected to lincomycin treatment showed a higher level of contraction. The phototaxis experiments revealed a light-induced behavioral of the anemones resulting in the their accumulation mainly under intermediate light intensities (16-50 μmol quanta mˉ² sˉ¹).