Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark.
Proc Biol Sci. 2023 Sep 27;290(2007):20230127. doi: 10.1098/rspb.2023.0127.
The jellyfish largely cover their carbon demand via photosynthates produced by microalgal endosymbionts, but how holobiont morphology and tissue optical properties affect the light microclimate and symbiont photosynthesis in remain unexplored. Here, we use optical coherence tomography (OCT) to study the morphology of 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 and show that granules enhance local light-availability for symbionts in close proximity. Individual granules had a scattering coefficient of = 200-300 cm, and scattering anisotropy factor of = 0.7, while large tissue-regions filled with white granules had a lower = 40-100 cm, and = 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 play an important role in the host modulation of the light-microenvironment.
水母主要通过共生微藻光合作用产生的光合产物来满足其碳需求，但共生体形态和组织光学特性如何影响光微环境和共生体光合作用尚不清楚。在这里，我们使用光学相干断层扫描（OCT）以高空间分辨率研究水母体的形态。我们包括对外部微观形态的详细 3D 重建，并显示了共生体和钟状组织中白色颗粒的空间分布。此外，我们使用 OCT 数据从 中的光散射白色颗粒中提取固有光学特性，并表明颗粒增强了近距离共生体的局部光可用性。单个颗粒的散射系数为 = 200-300 cm，散射各向异性因子为 = 0.7，而充满白色颗粒的大组织区域的 = 40-100 cm， = 0.8-0.9。我们将 OCT 信息与同位素标记实验相结合，研究了在白色组织区域增强光可用性的效果。与在有分支组织（即没有光散射白色颗粒的组织）中的共生体相比，位于白色组织中的共生体表现出明显更高的碳固定率。我们的发现支持了先前的观点，即 中的白色颗粒在宿主调节光微环境方面发挥着重要作用。
