Haplosporidiosis of the Pacific oyster, Crassostrea gigas

Carolyn S. Friedman, Deborah F. Cloney, Donald Manzer, Ronald Hedrick

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Haplosporidan parasites were observed in 10 100 spat and 1 171 adult Pacific oysters, Crassostrea gigas, reared in Matsushima Bay, Japan. Eight of the infected spat contained mild to severe plasmodial infections. The multinucleated plasmodia were 6-12 μm × 7-15 μm and were associated with an infiltration of hemocytes that occurred throughout the vesicular connective tissues of all infected oysters. Two oysters, one adult and one spat, contained advanced sporogonic infections. These were characterized by the presence of sporocysts and immature and mature operculated spores that measured 5.6-6.0 μm × 6.0-8.0 μm and were found exclusively within the digestive tubule epithelium. Electron microscopic examination revealed that mature spores contained a hinged operculum, striated and layered wall, spherule, single nucleus, and haplosporosome formative regions. Parasite morphology and infection pattern closely resemble that of Haplosporidium nelsoni, a pathogen of American oysters (C. virginica).

Original languageEnglish (US)
Pages (from-to)367-372
Number of pages6
JournalJournal of Invertebrate Pathology
Issue number3
StatePublished - Jan 1 1991


  • digestive tubule epithelium
  • haplosporidan
  • Pacific oyster Crassostrea gigas
  • plasmodia
  • spores
  • vesicular connective tissue

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


Dive into the research topics of 'Haplosporidiosis of the Pacific oyster, Crassostrea gigas'. Together they form a unique fingerprint.

Cite this