Thermal responses and Symbiodiniaceae shuffling in a Red Sea foraminifer holobiont
Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine
Abstract Symbiont-bearing benthic foraminifera, like corals, rely on endosymbionts for growth and nutrition and experience bleaching under heat stress., found in tropical and subtropical waters, hosts a diverse range of endosymbionts belonging to Symbiodiniaceae. We examined the thermal tolerance of the Red Sea population, which is the source of an established, invasive population ofin the Eastern Mediterranean. The Red Sea population is expected to exhibit enhanced thermotolerance, potentially due to its greater variety of endosymbionts. We conducted temperature-manipulation experiments, measuring calcification rates and net photosynthesis, evaluating the thermotolerance ofand its endosymbionts. We also analyzed the diversity of Symbiodiniaceae by sequencing the internal transcribed spacer 2 (ITS2). Our results show that exposure to 35°C initially induced stress in the endosymbionts during the first week; however, net photosynthesis gradually recovered in subsequent weeks. In contrast, host calcification rates remained low at 35°C, though not completely inhibited. Amplicon sequencing revealed that by the end of the experiment, a single ITS2 type, belonging to Symbiodiniaceaeand initially present in field-collected specimens, became dominant in cultured individuals. Because this type became dominant across all temperature treatments, the observed shift likely reflects a response to laboratory conditions rather than direct thermal selection. Consequently, although the recovery
Abstract
Abstract Symbiont-bearing benthic foraminifera, like corals, rely on endosymbionts for growth and nutrition and experience bleaching under heat stress., found in tropical and subtropical waters, hosts a diverse range of endosymbionts belonging to Symbiodiniaceae. We examined the thermal tolerance of the Red Sea population, which is the source of an established, invasive population ofin the Eastern Mediterranean. The Red Sea population is expected to exhibit enhanced thermotolerance, potentially due to its greater variety of endosymbionts. We conducted temperature-manipulation experiments, measuring calcification rates and net photosynthesis, evaluating the thermotolerance ofand its endosymbionts. We also analyzed the diversity of Symbiodiniaceae by sequencing the internal transcribed spacer 2 (ITS2). Our results show that exposure to 35°C initially induced stress in the endosymbionts during the first week; however, net photosynthesis gradually recovered in subsequent weeks. In contrast, host calcification rates remained low at 35°C, though not completely inhibited. Amplicon sequencing revealed that by the end of the experiment, a single ITS2 type, belonging to Symbiodiniaceaeand initially present in field-collected specimens, became dominant in cultured individuals. Because this type became dominant across all temperature treatments, the observed shift likely reflects a response to laboratory conditions rather than direct thermal selection. Consequently, although the recovery at 35°C is consistent with acclimatory physiological responses, it does not provide direct evidence for symbiont-specific acclimation. Our findings suggest that holobiont physiological recovery and symbiont shuffling under laboratory conditions may contribute to the resilience ofin warming oceans.