Victor Sprague

The fine structure of Nosema sp. Sprague, 1965 (Microsporida, Nosematidae) with particular reference to stages in sporogony

Abstract Stages of Nosema sp. occurring in the skeletal muscle of an experimentally infected crab, Callinectes sapidus , were observed by means of electron microscopy. Only diplokarya and stages in sporogony from sporoblasts to spores were seen. All these were extracellular. The fine structure was basically similar to that which has been reported for other Microsporida but there were some peculiar features. Chief of these were a new kind of polaroplast and a large cavity or “cavum” in which it was suspended. The polaroplast, a bipartite structure, had a compactly laminated anterior portion. This part had been seen in a previous study as a chromophilic body which, suspended in the cavum, resembled a coiled polar filament in a capsule. Another peculiarity was the presence of numerous short bristles emanating from the surfaces of the sporoblasts and spores. An inference that the zygote in Nosema gives rise to two sporoblasts suggests the need for reexamination of the definition of the genus and of some commonly used terms.

A new species of Paramoeba (Amoebida, Paramoebidae) parasitic in the crab Callinectes sapidus☆

Abstract Paramoeba sp. Sprague and Beckett, 1966 , is compared with Paramoeba eilhardi Schaudinn 1896, the type and only presently recognized species in the genus, and found to be distinct. The name Paramoeba perniciosa sp. n. is proposed. Distinctive characters of this species are its parasitic habit, its failure to survive in common culture media, its relatively small size, and its linguiform lobopodia.

The fine structure of Ameson pulvis (Microspora, Microsporida) and its implications regarding classification and chromosome cycle☆☆☆

Abstract Nosema pulvis Perez, 1905 , Ameson pulvis (Perez) Sprague, 1977 , in muscles of the crabs Carcinus maenas and C. mediterraneus from the coast of France, was observed with the electron microscope. It was found to be structurally similar to the type species A. michaelis ( Sprague, 1970 ). Sprague, 1977 , having moniliform sporogonial plasmodia, unikaryotic sporoblasts, and hirsute sporulation stages. It is treated as distinct from A. michaelis because it has slightly smaller spores (by comparison with syntype material of A. michaelis) and appears to have fewer coils in the polar filament. The results require the removal of the genus Ameson from the family Nosematidae Labbe, 1899, where Sprague (1977) had placed it under the erroneous supposition that its sporoblasts are diplokaryotic. Ameson is transferred to family Unikaryonidae Sprague, 1977 . Ameson is distinguished from Perezia Leger and Duboscq, 1909 , shown by Ormieres et al. to have a similar developmental pattern, by presence of appendages on its sporulation stage. A. nelsoni ( Sprague, 1950 ), the third, and only other species of Ameson, lacks the appendages and is transferred to genus Perezia.

Light and electron microscope study of a new species of Urosporidium (Haplosporida), hyperparasite of trematode sporocysts in the clam Abra ovata

Abstract Abra ovata , collected at Bcauduc, France, contained sporocysts of Gymnophallus nereicola and another trematode of the family Monorchiidae. Frequently the former trematode and occasionally the latter was infected with a species of Urosporidium . Stages observed were mostly in the sporogenesis sequence. The sporoblast, an elongated body of uncertain origin, differentiates into two parts delimited by a girdle-shaped constriction between them. These are an anterior part, or sporoplasm primordium, containing a vesicular nucleus and a posterior part, or envelope primordium, containing a “parietal apparatus” (possibly a transformed nucleus). Cytoplasm of the envelope primordium (just behind the constriction) advances to enclose the sporoplasm primordium while it differentiates into endospore, exospore and an internally situated cover over the orifice. These two primordia separate late in the sporogenesis sequence. Thus, the typical haplosporidan spore may, as Cepede reported in 1911, consist of 2 cells, a generative cell enveloped by a somatic cell. Evidence that the Haplosporida have bicellular spores raises fundamental questions regarding the taxonomy of this group.

Light and electron microscope study of a new species of Thelohania (Microsporida) in the shrimp Pandalus jordani

Abstract Thelohania butleri n. sp. was found in cells of skeletal muscles of the shrimp Pandalus jordani, from Queen Charlotte Sound, British Columbia, Canada. Sporulation stages were studied with the light and the electron microscope. Earliest stages were small and apparently uninucleate. Next were small diplokaryotic cells that possibly arose by fusion of the former. These enlarged and underwent sporogony. Sporogony was a series of three binary divisions, each producing unikaryotic cells. There was no sporogonial plasmodium. The spore was ovoid, 4.8 × 3.1 μm (stained), with a large crescentic nucleus and rounded posterior vacuole. The polar filament was isofilar, doubly coiled, with about 10 turns. This species closely resembles the type T. giardi Henneguy. It is concluded that sporogony by means of three binary divisions and lack of a sporogonial plasmodium may be essential characters of the genus Thelohania Henneguy, 1982.

A new family, new genus, and new species allied to the Microsporida

Abstract A new and unusual microsporidian species was found in the intestinal epithelium of dipteran larvae of genus Sciara. Merogony is by binary and multiple fission. Sporogonial plasmodia become enclosed in ornate, thick-walled cysts. The cyst contents become cut up by temporary cytoplasmic partitions to make numerous binucleate cells (sporonts) Each divides to produce one normal and one abortive sporoblast. Because this species has a number of unusual features, a new family and a new genus are proposed to contain it.

A new species of Pleistophora (Microsporida: Pleistophoridae) parasitic in the shrimp Palaemonetes pugio

Abstract Pleistophora sp. Sprague, 1970 , in the muscle of Palaemonetes pugio was studied. Formalin fixed spores were ellipsoidal, 2.5–3.3 × 1.4–2.0 μm, and with large anterior and posterior clear areas representing the polaroplast and posterior vacuole. This species, after comparison with four other species of Pleistophora in decapod crustacea, was found to be new. It is named Pleistophora lintoni n. sp.