title: Physiological and biochemical performances of menthol-induced aposymbiotic corals.
abstract: The unique mutualism between corals and their photosynthetic zooxanthellae (Symbiodinium spp.) is the driving force behind functional assemblages of coral reefs. However, the respective roles of hosts and Symbiodinium in this endosymbiotic association, particularly in response to environmental challenges (e.g., high sea surface temperatures), remain unsettled. One of the key obstacles is to produce and maintain aposymbiotic coral hosts for experimental purposes. In this study, a simple and gentle protocol to generate aposymbiotic coral hosts (Isopora palifera and Stylophora pistillata) was developed using repeated incubation in menthol/artificial seawater (ASW) medium under light and in ASW in darkness, which depleted more than 99% of Symbiodinium from the host within 4∼8 days. As indicated by the respiration rate, energy metabolism (by malate dehydrogenase activity), and nitrogen metabolism (by glutamate dehydrogenase activity and profiles of free amino acids), the physiological and biochemical performances of the menthol-induced aposymbiotic corals were comparable to their symbiotic counterparts without nutrient supplementation (e.g., for Stylophora) or with a nutrient supplement containing glycerol, vitamins, and a host mimic of free amino acid mixture (e.g., for Isopora). Differences in biochemical responses to menthol-induced bleaching between Stylophora and Isopora were attributed to the former digesting Symbiodinium rather than expelling the algae live as found in the latter species. Our studies showed that menthol could successfully bleach corals and provided aposymbiotic corals for further exploration of coral-alga symbioses.
authors.affiliation: Graduate Institute of Biotechnology, Tajen University, Pingtung, Taiwan. jtw@mail.tajen.edu.tw
authors.forename: Jih-Terng
authors.initials: JT
authors.lastname: Wang
authors.forename: Yi-Yun
authors.initials: YY
authors.lastname: Chen
authors.forename: Kwee Siong
authors.initials: KS
authors.lastname: Tew
authors.forename: Pei-Jei
authors.initials: PJ
authors.lastname: Meng
authors.forename: Chaolun A
authors.initials: CA
authors.lastname: Chen
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000187:drug effects / Q000502:physiology*; D019069:Cell Respiration / Q000502:physiology; D057894:Coral Reefs; D004141:Dinoflagellida / Q000187:drug effects / Q000502:physiology*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D008027:Light; D008291:Malate Dehydrogenase / Q000378:metabolism; D008610:Menthol / Q000494:pharmacology*; D009792:Oceans and Seas; D010788:Photosynthesis; D012623:Seawater; D013045:Species Specificity; D013559:Symbiosis; D013696:Temperature
chemical_list: D008610:Menthol; D008291:Malate Dehydrogenase; D005969:Glutamate Dehydrogenase