Ultrastructure of Amoebophrya sp. and its changes during the course of infection

Protist. 2012 Sep;163(5):720-45. doi: 10.1016/j.protis.2011.11.007. Epub 2011 Dec 29.


Amoebophrya is a syndinian parasite that kills harmful bloom forming algae. Previously uncharacterized ultrastructural aspects of infection and development were elucidated. The biflagellate dinospore has two mitochondria, electron-dense bodies, striated strips, trichocysts, and a nucleus with peripherally condensed chromatin. After finding an Akashiwo sanguinea host and adhering to its surface, the parasite penetrates the host surface, apparently using a microfilament based motility and electron-dense bodies within a microtubular basket in the process of parasitophorous vacuole membrane formation. After entering the host nucleus, possibly by a similar mechanism used to enter the host cell, the parasite cytosol expanded substantially prior to mitosis. From 12-36 hours mitochondria were inconspicuous but present. Chromatin condensation was variable. By 36 hours post-infection, parasites had multiple nuclei, a microtubule-supported cytopharynx, and were beginning to form a fully internal mastigocoel. By 48 hours, the characteristic "beehive" appearance was apparent with flagella projecting into a fully developed mastigocoel. The cytoplasm contained trichocysts, elongated mitochondria, and nuclei with peripherally condensed chromatin. Although Amoebophrya lacks an apical complex, its electron-dense bodies show functional similarities to apicomplexan rhoptries. Its lack of permanently condensed chromosomes, but compact dinospore chromatin, supports the idea that dinoflagellate permanently condensed chromosomes may be a remnant of a parasitic ancestor with a compact dispersal stage.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alveolata / growth & development
  • Alveolata / isolation & purification
  • Alveolata / ultrastructure*
  • Chromatin / ultrastructure
  • Microscopy, Confocal
  • Microscopy, Electron, Scanning
  • Microscopy, Electron, Transmission
  • Organelles / ultrastructure


  • Chromatin