Cytological Observations of the Large Symbiotic Foraminifer Amphisorus kudakajimensis Using Calcein Acetoxymethyl Ester

PLoS One. 2016 Nov 3;11(11):e0165844. doi: 10.1371/journal.pone.0165844. eCollection 2016.

Abstract

Large benthic foraminifera are unicellular calcifying reef organisms that can form symbiotic relationships with a range of different microalgae. However, the cellular functions, such as symbiosis and calcification, and other aspects of cellular physiology in large benthic foraminifera are not fully understood. Amphisorus kudakajimensis was used as a model to determine the detailed cellular characteristics of large benthic foraminifera. We used calcein acetoxymethyl ester (calcein AM) as a fluorescent indicator for live confocal imaging. We demonstrated that calcein AM is a useful fluorescent indicator to stain the fine network of reticulopodia and the cytoplasm in living A. kudakajimensis. We showed that at least two types of reticulopodia exist in A. kudakajimensis: the straight bundle of reticulopodia that spreads from the aperture and the fine reticulopodia along the surface of the aperture and chamber walls. The cytoplasm in outer chambers was highly branched and contained a few dinoflagellates. In contrast, the inner chamberlets contained condensed cytoplasm and many dinoflagellates, suggesting that the cytoplasm of A. kudakajimensis performs different functions based on its location within the large test. Our confocal detailed image analysis provides real-time cellular morphology and cell physiology of living foraminifera.

MeSH terms

  • Cytoplasm / metabolism
  • Fluoresceins / metabolism*
  • Foraminifera / cytology*
  • Foraminifera / metabolism*
  • Foraminifera / physiology
  • Optical Imaging*
  • Staining and Labeling
  • Symbiosis*

Substances

  • Fluoresceins
  • calcein AM

Grants and funding

This work was supported by KAKENHI (24340131), Grant-in-Aid for JSPS Fellows (15J04797), URL: https://www.jsps.go.jp/english/e-grants/; and The International Research Hub Project for Climate Change, and Coral Reef/Island Dynamics Department of the University of the Ryukyus, and the University of the Ryukyus Foundation, URL: http://www.u-ryukyu.ac.jp/en/.