Cryopreservation of six Symbiodiniaceae genera and assessment of fatty acid profiles in response to increased salinity treatments

Abstract

Symbiodiniaceae are a diverse group of dinoflagellates, the majority of which are free-living and/or associated with a variety of protists and other invertebrate hosts. Maintenance of isolated cultures is labour-intensive and expensive, and cryopreservation provides an excellent avenue for their long-term storage. We aimed to cryopreserve 15 cultured isolates from six Symbiodiniaceae genera using dimethyl sulfoxide (DMSO) as the cryoprotectant agent (CPA). Under 15% DMSO, 10 isolates were successfully cryopreserved using either rapid freezing or controlled-rate freezing. Cultures that failed or had low survival, were subjected to (1) a reduction of CPA to 10%, or (2) increased salinity treatment before freezing. At 10% DMSO, three further isolates were successfully cryopreserved. At 15% DMSO there were high cell viabilities in Symbiodinium pilosum treated with 44 parts per thousand (ppt) and 54 ppt culture medium. An isolate of Fugacium sp. successfully cryopreserved after salinity treatments of 54 ppt and 64 ppt. Fatty acid (FA) analyses of S. pilosum after 54 ppt salinity treatment showed increased saturated FA levels, whereas Fugacium sp. had low poly-unsaturated FAs compared to normal salinity (34 ppt). Understanding the effects of salinity and roles of FAs in cryopreservation will help in developing protocols for these ecologically important taxa.

Developing model systems for dinoflagellates in the post‐genomic era

“…Although monoclonal cultures are available from major culture collections, most dinoflagellate strains are cryo‐recalcitrant (Paredes et al, 2021), limiting their tractability as models. Attempts at cryopreservation have been successful for some Symbiodiniaceae strains (Di Genio et al, 2021; Kihika et al, 2022), but generalizability to other dinoflagellate taxa remains to be investigated.…”

First successful production of adult corals derived from cryopreserved larvae

“…In vitrification, the sample solidifies without ice crystals, and multiple (Tsai et al, 2016b;Jang et al, 2017;Magnotti et al, 2018) or no CPAs (Isachenko et al, 2003;Spis et al, 2019) are used for biological samples that require extremely high cooling rates (Bojic et al, 2021). Vitrification was first used in mouse (Mus musculus) embryos (Rall and Fahy, 1985) and then plants (Stiles, 1930), erythrocytes (Rapatz and Luyet, 1968), mammalian embryos (Rall and Fahy, 1985;Massip et al, 1986;Yuswiati and Holtz, 1990;Rall, 1993;Schiewe and Anderson, 2017), fish (Cuevas- Uribe et al, 2013;Figueroa et al, 2013;Godoy et al, 2013), invertebrates (Guo and Weng, 2020;Heres et al, 2021), and now corals (Tsai et al, 2015) and their unicellular dinoflagellate symbionts (di Genio et al, 2020;Kihika et al, 2022a;Kihika et al, 2022b). Researchers are striving to cryobank genetic materials from endangered coral species and save regional populations in decline.…”