In vivoimaging of coral tissue and skeleton with optical coherence tomography

Abstract

statement: We use optical coherence tomography to study the microstructural properties of coral tissues and skeletons.OCT imaging of corals Abstract Optical coherence tomography (OCT) is a non-invasive three-dimensional imaging technique with micrometer resolution allowing microstructural characterization of tissues in vivo and in real time. We present the first application of OCT for in vivo imaging of tissue and skeleton structure of intact living corals spanning a variety of morphologies and tissue thickness. OCT visualized different coral tissue layers (e.g. endoderm vs ectoderm), special structures such as mesenterial filaments and skeletal cavities, as well as mucus release from living corals. We also developed a new approach for noninvasive imaging and quantification of chromatophores containing green fluorescent protein (GFP)-like host pigment granules in coral tissue. The chromatophore system is hyper-reflective and can thus be imaged with good optical contrast in OCT, enabling quantification of chromatophore size, distribution and abundance. Because of its rapid imaging speed, OCT can also be used to quantify coral tissue movement showing that maximal linear contraction velocity was ~120 μm per second upon high light stimulation. Based on OCT imaging of tissue expansion and contraction, we made first estimates of dynamic changes in the coral tissue surface area, which varied by a factor of 2 between the contracted and expanded state of the coral Pocillopora damicornis. We conclude that OCT is an excellent novel tool for in vivo tomographic imaging of corals that can reveal tissue and skeleton organization as well as quantify dynamic changes in tissue structure and coral surface area non-invasively and at high spatio-temporal resolution.

Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light

“…In spite of this difference in overall acclimation to light, a decrease in the surface layer photosynthesis was seen in the coral sediment at an incident irradiance of 500 μmol photons m −2 s −1 , which could either reflect the heterogeneity and patchiness of the phototrophs found in the sediment, or could point to a possible migration of motile phototrophic organisms. Migration as a phototactic response is recognized as an effective mechanism for controlling photon absorption across different systems such as terrestrial plants (Wada et al, 2003) and microphytobenthic assemblages (Serodio et al, 2006; Cartaxana et al, 2016a,b), and similar phototactic response has been shown in coral tissues where the in hospite light environment can be modulated by host tissue movement (Wangpraseurt et al, 2014a, 2017). Downward migration at high irradiances is probably correlated with increasing photic stress e.g., by the formation of reactive oxygen species that can damage photosystem II by preventing the synthesis of the D1 protein in these layers (Hihara et al, 2001; Nishiyama et al, 2001; Aarti et al, 2007; Latifi et al, 2009; Al-Najjar et al, 2010).…”

In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?

“…Although, P. damicornis does also have a GFP-like pigment (Takabayashi and Hoegh-Guldberg, 1995), the GFP-like pigments in Favites sp. are arranged in a chromatophore system that strongly enhances light scattering (Lyndby et al, 2016; Wangpraseurt et al, 2016b) facilitating a steep light attenuation along the enhanced optical path within thick scattering coral tissue (Wangpraseurt et al, 2012; Lyndby et al, 2016). Our finding of low light levels in the aboral polyp tissues therefore suggests that tissue background scattering and absorption effectively attenuate light even in bleached tissues of Favites sp.…”

Optical coherence tomography in biofilm research: A comprehensive review

“…To the authors knowledge there is only the publication of Wangpraseurt et al (bioRxiv) who introduced this approach describing the expansion and compaction of coral tissue. A change of the surface area by a factor of two was determined.…”