Upcoming

DinoSphere Online Seminar – 18th of June 2026 at 9 am (PDT) / 6 pm (CEST)

On our upcoming DinoSphere seminar will be on June 18th at 9 am (PDT) / 6 pm (CEST) with  presnetation by Jana Pilátová (Lawrence Berkeley National Laboratory) and Grace Zhong (University of British Columbia). 

Zoom link will be available closer to the date 

Jana Pilátová 

Long-range actin-driven mobility of dinoflagellate symbionts in an animal-algal symbiosis

Established symbionts in animal-microbe symbioses are often thought to be confined to a niche and generally lose their motile appendages such as flagella. Whether this loss implies immobility within the animal host remains an open conundrum. We discover long-range, host-mediated symbiont mobility in a dinoflagellate-acoel worm symbiosis. Using long-term tracking, fluorescence, and electron microscopy, we find that hundreds of dinoflagellate symbionts (Amphidinium sp., 10-20 𝝁𝒎 in size) travel across the entire body of an acoel worm host (Waminoa sp.) at high velocities (around 1 𝝁𝒎/𝒔) while under high confinement inside a network of ultra-thin host parenchymal cells (∼200 𝒏𝒎 thin). We unveil the molecular mechanism of this mobility to be host actin machinery. We further reveal spatiotemporal regulation of symbiont distribution associated with diel rhythms and during regeneration. We establish the presence of host-mediated mobility in animal-microbe symbioses, which suggests the existence of previously overlooked regulatory processes in holobionts’ maintenance of dynamic homeostasis.

Grace Zhong

Microbial vision in Symbiodiniaceae, eyespots acting as photonic mirrors

The free-living dinoflagellate Effrenium voratum (Symbiodiniaceae, Dinoflagellata, Alveolata, SAR) forms a type E eyespot composed of microscopic crystals. This eyespot type is widespread across Suessiales, a group distributed from tropical to polar waters and from marine to freshwater habitats, encompassing free-living species as well as symbionts and parasites. The crystals forming the eyespot have previously been identified as uric acid. However, our Raman microscopy analyses revealed that these crystals instead consist of β-polymorphic anhydrous guanine. Super-resolution imaging of the highly reflective guanine crystals using interference reflectance microscopy (IRM) provided real-time insight into crystal dynamics within the eyespot. Due to their high refractive index (1.83), guanine crystals can alternate with the low-refractive-index cytoplasm (1.34) to form multilayered photonic mirrors capable of constructive light interference, depending on layer thickness. Transmission electron microscopy (TEM) and tomography revealed layer thicknesses of approximately 85 ± 20 nm. This structural information enabled simulations of reflectance spectra using finite-difference time-domain optical modeling, resulting in reflectance maxima between 500 and 550 nm. Complementary data-driven machine learning predictions of absorbance spectra for photoreceptive rhodopsins showed a corresponding spectral match. These findings are consistent with empirical studies demonstrating that phototaxis is both intensity- and wavelength-dependent, with maximal attraction toward green light, the dominant wavelength range in marine environments.