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Treatment of fish parasites

II. Morphogenesis ofHenneguya laterocapsulata Landsberg, 1987 (Myxosporea, Myxozoa), and the effects of a new triazine derivative, HOE 092 V, on its developmental stages: a light and electron microscopy study


The ultrastructure of sporogenesis was studied inHenneguya laterocapsulata parasitizing the skin of hybrid catfish (Clarias gariepinus x Heterobranchus bidorsalis) in Nigeria. Sporogenesis started when a generative cell was surrounded by a second nondividing cell (i.e., envelope cell). By subsequent divisions of the generative cell, ten cells were produced, which finally became arranged into two spore-producing units. Each unit consisted of a binucleate sporoplasm, two capsulogenic cells, and two valvogenic cells. Apparently capsulogenesis, valvogenesis, and sporoplasm differentiation occurred concomitantly. In research for chemotherapy of fish parasitized by myxosporeans a new triazine derivative, 2-[3,5-α-dichloro-4-(4-methyl-sulfonylphenoxy)-phenyl]-1-methyl-hexahydro-1, 2, 4-triazine-3,5-dion (HOE 092 V), was tested in vivo against the uni- and multicellular developmental stages ofH. laterocapsulata. Naturally infected catfish were incubated in water containing 0, 2.5, 5, and 10 μg HOE 092 V/ml or the pure solvent for 3 h. After the fish had been returned into fresh water, they were killed 1 day after the treatment and the plasmodia were studied by means of light and transmission electron microscopy. Starting with a dose of 2.5 μg HOE 092 V/ml, the pericyte's outer membrane was broken in the bi- and multicellular stages. The number of ribosomes in the bi- and multicellular stages decreased. In the multicellular stages the rough endoplasmic reticula of the capsulogenic cells were enlarged. Treatment with 5 μg HOE 092 V/ml led to breaks in the limiting outer membranes of the capsulogenic cells and to vacuolization of their peripheral cytoplasm. In early prespore stages a decrease in the number of spherical inclusions was recognized. After treatment with 10 μg HOE 092 V/ml the degree of the damage increased and the sporoplasm of the nearly mature pansporoblast shrank. The pure solvent had no effect on either the plasmodia or the uni- and multicellular stages. These results suggest that chemotherapy againstH. laterocapsulata and other myxozoan species should be accomplished by bathing the fish in aerated containers with 5 or 10 μg HOE 092 V/ml for 3 h. This treatment will considerably reduce the production of spores.

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chromatin aggregations


capsulogenic cell


capsular primordium


destruction of the limiting membrane


electron-dense body


envelope cell




generative cell










polar capsule


perinuclear space




rough endoplasmic reticulum




sutural ridge


thickenings of the limiting cell membrane


vacuole caused by treatment


valvogenic cell


material forming the valve


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Correspondence to Günter Schmahl.

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Schmahl, G., Obiekezie, A. & Raether, W. Treatment of fish parasites. Parasitol Res 79, 667–674 (1993).

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  • Outer Membrane
  • Dion
  • Triazine
  • Generative Cell
  • Rough Endoplasmic Reticula