Foraminiferal ultrastructure: A perspective from fluorescent and fluorogenic probes

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Biogeosciences 124 (2019): 2823-2850, doi:10.1029/2019JG005113.Microscopy techniques have been widely applied to observe cellular ultrastructure. Most of these techniques, such as transmission electron microscopy, produce high‐resolution images, but they may require extensive preparation, hampering their application for in vivo examination. Other approaches, such as fluorescent and fluorogenic probes, can be applied not only to fixed specimens but also to living cells when the probes are nontoxic. Fluorescence‐based methods, which are generally relatively easy to use, allow visual and (semi)quantitative studies of the ultrastructural organization and processes of the cell under natural as well as manipulated conditions. To date, there are relatively few published studies on the nearly ubiquitous marine protistan group Foraminifera that have used fluorescent and fluorogenic probes, despite their huge potential. The aim of the present contribution is to document the feasible application of a wide array of these probes to foraminiferal biology. More specifically, we applied fluorescence‐based probes to study esterase activity, cell viability, calcium signaling, pH variation, reactive oxygen species, neutral and polar lipids, lipid droplets, cytoskeleton structures, Golgi complex, acidic vesicles, nuclei, and mitochondria in selected foraminiferal species.The authors are very grateful to the Editor‐in‐Chief Miguel Goni and two anonymous reviewers for their thoughtful and valuable comments that have greatly improved the paper. Markus Raitzsch and Karina Kaczmarek from the AWI, Jakub Kordas from the ZOO Wrocław sp. z o. o. (Poland), and Max Janse from The Royal Burgers' Zoo (Arnhem, the Netherlands) are gratefully acknowledged. The authors declare that no competing interests exist. All the data are included within the paper or the supporting information accompanying it. The research for this paper was partially supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (PRIN 2010‐2011 protocollo 2010RMTLYR) to R.C., the Japan Society for the Promotion of Science KAKENHI Grant (Numbers: JP18H06074, JP17H02978, JP19H02009, JP19H03045) to T.T. and Y.N., the WHOI Investment in Science Program to J.M.B, the Polish National Science Center (Grant DEC‐2015/19/B/ST10/01944) J.T. and J.G. and the Kuwait Foundation for the Advancement of Sciences (EM084C) to E.A‐E.2020-02-2