Symbiotic nutrient exchange enhances the long-term survival of cassiosomes, the autonomous stinging-cell structures of .

Medusae of the widely distributed upside-down jellyfish release autonomous, mobile stinging structures. These so-called cassiosomes play a role in predator defense and prey capture, and are major contributors to "contactless" stinging incidents in (sub-)tropical shallow waters. While the presence of endosymbiotic dinoflagellates in cassiosomes has previously been observed, their potential contribution to the metabolism and long-term survival of cassiosomes is unknown.

Non-invasive investigation of the morphology and optical properties of the upside-down jellyfish with optical coherence tomography.

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.

Green fluorescent protein-like pigments optimise the internal light environment in symbiotic reef-building corals.

Pigments homologous to the green fluorescent protein (GFP) have been proposed to fine-tune the internal light microclimate of corals, facilitating photoacclimation of photosynthetic coral symbionts (Symbiodiniaceae) to life in different reef habitats and environmental conditions. However, direct measurements of the in vivo light conditions inside the coral tissue supporting this conclusion are lacking. Here, we quantified the intra-tissue spectral light environment of corals expressing GFP-like proteins from widely different light regimes.

Amoebocytes facilitate efficient carbon and nitrogen assimilation in the -Symbiodiniaceae symbiosis.

The upside-down jellyfish engages in symbiosis with photosynthetic microalgae that facilitate uptake and recycling of inorganic nutrients. By contrast to most other symbiotic cnidarians, algal endosymbionts in are not restricted to the gastroderm but are found in amoebocyte cells within the mesoglea. While symbiont-bearing amoebocytes are highly abundant, their role in nutrient uptake and cycling in remains unknown.

Heat generation and light scattering of green fluorescent protein-like pigments in coral tissue.

Green fluorescent protein (GFP)-like pigments have been proposed to have beneficial effects on coral photobiology. Here, we investigated the relationships between green fluorescence, coral heating and tissue optics for the massive coral Dipsastraea sp. (previously Favia sp.