DAO 54:203-207 (2003)  -  doi:10.3354/dao054203

Ultrastructural details of the xenoma of Loma myrophis (phylum Microsporidia) and extrusion of the polar tube during autoinfection

E. Matos1, L. Corral2,3, C. Azevedo2,3,*

1Department of Animal Biology, Federal Rural University of the Amazonia, Belém, Brazil
2Department of Cell Biology, Institute of Biomedical Sciences, and
3CIIMAR ‹ Centre for Marine and Environmental Research, University of Oporto, Lg. Abel Salazar no. 2, 4099-003 Porto, Portugal
*Corresponding author. Email:

ABSTRACT: Xenomas of the recently described new microsporidian species Loma myrophis parasitizing the gut tissue of the Amazonian fish Myrophis platyrhynchus (family Ophichthidae) were described by light- and transmission-electron microscopy. The xenoma consisted of a thin fibrillar wall that surrounded a hypertrophic host cell cytoplasm containing numerous microsporidian developmental stages and spores. Several spores showed different stages of natural extrusion of the polar tube. Numerous longitudinal and transverse sections of the extruded polar tubes were observed in developing life-cycle stages (spores excepted), the nucleus of hypertrophic host cell, the xenoma wall and surrounding fibroblasts. The extruded polar tubes were projected in all directions with no preferential orientation. These aspects suggested that autoinfection occurred within this xenoma.

KEY WORDS: Ultrastructure · Microsporidian · Xenoma · Extrusion · Polar tube · Loma myrophis · Parasite

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