Electron microscopical study of a new genus and new species of microsporida in the gills of Atlantic cod Gadus morhua L.*

Abstract

A microsporidium, forming xenoparasitie complexes (xencmas) of the cell-hypertrophy tumour type, was found in the gills of the Atlantic cod Gadus morhua L. and studied with the electron microscope. It seemed to be similar to Nosema branehiale Nemeezek, 1911, in the haddock Melanogrammus aeglefinus (L.) except in size of spore. The xenoma (cyst) was basically like the Glugea eyst and the parasite had some other characters in common with Glugea; it was apansporoblastie, unikaryotic, disporoblastie and underwent partial development in parasitophorous vacuoles. It differed from Glugea in lacking plasmodial stages, producing usually 1 or 2 spores (rather than 16) in a vacuole, showing no distinct tendency for different stages to occur in different zones of the cyst and having tubules in the parasitophorous vacuoles. The name Loma morhua n. g., n. sp. (type) was proposed and the genus assigned to the family Glugeidae Thelohan. 1892. The parasite of haddock gill was transferred to the new genus, becoming L. branchiaUs (Nemeezek, 1911) n. comb.

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

“…This complex structure is defined by the formation of a HHC containing intracellular microsporidian parasites and a HBN (Weissenberg 1949, 1968, 1976, Canning 1976, Dyková & Lom 1978. The features we observed in the xenoma of the microsporidian Loma myrophis (Azevedo & Matos 2002) are similar to those published in studies on other fish species (Morrison & Sprague 1981, Lom & Pekkarinen 1999.…”

“…In our observations, the presence of different sizes of xenoma, of which only the biggest with mature spores had numerous EPT, suggests that autoinfection may occur within the HHC (Morrison & Sprague 1981, Lom & Pekkaninen 1999.…”

“…This term, introduced by Weissenberg (1949), characterizes a wall of host origin surrounding the dividing parasite in the original parasitized host cell, which becomes hypertrophic with a hypertrophic nucleus. In the cytoplasm of the hypertrophic host cell (HHC), the parasite divides repeatedly, producing an enlarged xenoma containing numerous spores and other life-cycle stages (Morrison & Sprague 1981, Lom & Pekkarinen 1999. In a recent paper by Lom (2002), a complete list of microsporidians parasitic in fish was published.…”

Microsporidian xenomas in fish seen in wider perspective

“…Type species: G. anomala in Gasterosteus aculeatus. (Weidner 1976, Canning et al 1982, Takvorian and Cali 1983, Morrison et al 1985 1981a, b, 1983, Bekhti 1984 (Figs. 6, 8, 16).…”

Sur l’évolution des xénomes et le double rôle des polynucléaires neutrophiles dans la microsporidiose àGlugea stephani(Hagenmüller, 1899) chez le fletPlatichthys flesus(Linné, 1758)

“…Des réactions cellulaires du Poisson-hôte contre leur Microsporidie ont été signalées chez Crenilabrus melops parasité par Glugea gigantea (Mercier, 1921), Osmerus mordax parasité par Glugea hertwigi (Fantham, Porter et Richardson, 1941), Silurus glanis parasité par Nosema fennica (Lom et Weiser, 1969), Hippocampus erectus parasité par Glugea heraldi (Blasiola, 1979), Lophius americanus parasité par Spraguea lophii (Lom, 1972), Gadus pallachius et G. morhua parasités respectivement par Loma branchialis et L. morhua (Lom, 1972 ;Morrison et Sprague, 1981), Leiostomus xanthurus parasité par Ichthyosporidium giganteum (Sprague et Hussey, 1980), Gambusia affinis parasité par Glugea sp. (Crandal et Bowser, 1981).…”