DOI: 10.5061/dryad.jwstqjqgc
title: Non-invasive investigation of the morphology and optical properties of the upside-down jellyfish Cassiopea with optical coherence tomography

description: The jellyfish Cassiopea largely cover their carbon demand via
 photosynthates produced by microalgal endosymbionts, but how holobiont
 morphology and optical properties affect the light microclimate and
 symbiont photosynthesis in Cassiopea remain unexplored. Here, we use
 optical coherence tomography (OCT) to study the morphology of Cassiopea
 medusae at high spatial resolution. We include detailed 3D reconstructions
 of external micromorphology, and show the spatial distribution of
 endosymbionts and white granules in the bell tissue. Furthermore, we use
 OCT data to extract inherent optical properties from light-scattering
 white granules in Cassiopea, and show that white granules enhance local
 light-availability for symbionts in close proximity. Individual granules
 had a scattering coefficient of µs = 200-300 cm-1, and scattering
 anisotropy factor of g = 0.7, while large tissue-regions filled with white
 granules had a lower µs = 40-100 cm-1, and g = 0.8-0.9. We combined OCT
 information with isotopic labelling experiments to investigate the effect
 of enhanced light-availability in whitish tissue regions. Endosymbionts
 located in whitish tissue exhibited significantly higher carbon fixation
 compared to symbionts in anastomosing tissue (i.e., tissue without
 light-scattering white granules). Our findings support previous
 suggestions that white granules in Cassiopea play an important role in the
 host modulation of the light-microenvironment.
description: .oct datafiles included in this repository are to be used with
 the software "ThorImage OCT" from Thorlabs GmbH. All data
 provided here were acquired with ThorImage OCT version 5.1.2.0.
 For people without access to the ThorImage OCT software all data
 files are also provided in a .tiff format to be used in ImageJ.
description: # Non-invasive investigation of the morphology and optical properties of
 the upside-down jellyfish <i>Cassiopea</i> with optical
 coherence tomography: *** ## Description of the Data and file structure
 This dataset includes raw OCT data files of the animals and morphological
 structures presented in the manuscript published. Files are provided in
 two formats: 1. in the original raw .OCT data files as generated using the
 ThorImageOCT version 5.1.2.0 software provided for users of the Thorlabs
 Ganymede OCT system. 2. in 32-bit .tiff file format to be opened in
 ImageJ. This file format is for people that do not have access to the
 ThorImageOCT software, and contains all the raw data information as the
 original files, but lacks the complete 3D view function and additional
 features of the ThorImageOCT software. All files uploaded here represent
 the raw data of 2D and 3D scans of intact *Cassiopea* jellyfish, as well
 as cut-out regions of select tissue regions, used for this study (figures
 1-5 and supplementary figure 3). All files are named with their respective
 figure number and panel (if applicable). A brief description of each
 figure is found below, but for more detail of the anatomy of *Cassiopea*
 please see the supplementary material provided by Proceedings B, as well
 as the main text for further details on each figure and methods applied:
 **Figure 1** \| 3D scan of an entire juvenile *Cassiopea* sp. medusa,
 using a FOV of 7×7×2.8 mm (X-Y-Z), a resolution of 350×350×1024 pixels,
 corresponding to a voxel size of 20×20×2.74 µm. A pre-made, animated 3D
 representation of this figure can be found in the supplementary material
 provided by Proceedings B (Movie 1). **Figure 2** \| Rhopalia of
 *Cassiopea* medusae of \~4 cm (a) and \~1 cm (c) in diameter. (b) 2D scan
 of the rhopalium observed in panel (a). Panel (c-e) is of a smaller
 medusae, where the rhopalia canal is observed forking out into two parts
 that surround the rhopalium. **Figure 3** \| \(a\) 3D scan of an oral arm
 with clearly formed oral groove\, as well as oral vesicles and secondary
 mouths covered in frigid digitata\. \(b\) closeup of vesicle with a
 developing cluster of cassiosomes\. **Figure 4** \| \(a\) OCT scan of bell
 tissue with part of the subumbrella epidermis and mesoglea removed to
 improve scan penetration depth and clarity in this area\. \(b\) Overview
 of bell tissue with subumbrella layer removed\. The remaining gastrodermis
 from the radial canals was still attached to the exumbrella mesoglea
 showing how these canals branch out over the entire bell\. A dense carpet
 of white granules was found in the exumbrella mesoglea underneath radial
 canals\. **Figure 5** \| \(a\) 3D scan of a rhopalia canal with the
 subumbrella layer removed\, revealing the density of symbiont clusters in
 anastomosing tissue *vs*. white granules in this tissue area. Panel (b) is
 derived from panel (a) and represents a single tomographic section to
 illustrate the different densities of symbiont clusters and white
 granules. (c) closeup-scan of symbiont clusters. (d) closeup-scan of white
 granules. A pre-made, animated 3D representation of figure 5a can be found
 in the supplementary material provided by Proceedings B (Movie 2). **Fig.
 S3** \| \(a\) Overview of an intact vesicular lappet submerged in pure
 glycerol\. \(b\) Cross\-sectional scan of the lappet\.