Fig. 1: Intracellular development of the marine parasite Amoebophrya (Syndiniales) inside its microalgal host (the dinoflagellate Scrippsiella acuminata) unveiled by volume electron microscopy (FIB-SEM: Focused-Ion beam Scanning Electron Microscopy).
A 3D reconstruction of the first infection stage (cytoplasmic parasite) in the host cytoplasm where the parasite displayed a relatively small mitochondrion and condensed chromatin (heterochromatin) at the periphery of the nucleus (Scale bar: 2 µm). B, C The parasite then invaded the host nucleus where it developed from a young (B) to a mature trophont (C): the volumes of the parasite, its nucleolus and mitochondrion increased. The Golgi apparatus and nucleus division only appear in the mature trophont. (Scale bar: 2 µm). D The sporont parasite exhibited multiple nuclei (without visible nucleolus) and Golgi apparatus, and an extended mitochondrion that is dispersed throughout the whole parasite cell volume. Trichocysts were also synthetized at this stage, which are involved in host attachment for new infection. (Scale bar: 2 µm). Brown: parasite volume; light blue: nucleolus; Red: mitochondrion; dark blue: heterochromatin; green: Golgi apparatus; Yellow: trichocysts. E–H Volume of the parasite and its organelles (nucleus, nucleolus, mitochondrion) assessed after FIB-SEM-based 3D reconstruction (µm3) from four cytoplasmic parasites, seven young trophonts, one mature trophont and one sporont. See also Table S1 for morphometrics data.
