Menthol-DCMU bleaching and re-inoculation of Symbiodiniaceae in the large benthic foraminifera Sorites orbiculus

Sorites orbiculus specimens were collected on 26 July 2023 from the Gulf of Aqaba at the Interuniversity Institute for Marine Sciences in Eilat. In a controlled laboratory setting at the Leibniz Institute for Tropical Marine Research MAREE facility, these specimens underwent a bleaching process using 0.19 mmol L-1 menthol and 5 µmol L-1 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) over 27 days. Post-bleaching, the specimens were re-inoculated for 19 days with the Symbiodiniaceae strains Symbiodinium microadriaticum (strains CCMP2467 and KB8) and Fugacium kawagutii (strain F2) at a concentration of 1 × 10⁵ cells mL⁻¹. Subsequently, the specimens were cultivated for an additional 37 days to assess the stability of the newly established symbiotic associations. Throughout the experiment, physiological parameters were monitored using confocal laser scanning microscopy, pulse-amplitude modulated fluorometry, standard microscopy, motility assessments, and real-time quantitative polymerase chain reaction to confirm symbiont identity.