Iva Dyková

Sphaerospora renicola n.sp., a myxosporean from carp kidney, and its pathogenicity

Sphaerospora renicola n.sp. is a common parasite of carp in Czechoslovakia. Its life cycle involves intracellular stages in the epithelial cells of renal tubuli and trophozoite stages proliferating in the tubular lumen, transforming ultimately into pansporoblasts, each having one pansporoblast nucleus and producing two spores. The spores are almost globular with an average size of 7.3×7.2 μ, with polar capsules of equal size, and may have two slightly protruding tubercles on their shell valves. Differential diagnosis from otherSphaerospora species infecting carp, as well as fromMitraspora cyprini Fujita, is made. Intracellular stages ofS. renicola cause swelling and hyperplasia of the epithelium in renal tubuli followed by dystrophic changes. Accumulation of developmental stages in the tubular lumen provokes pronounced regressive changes of the epithelium, which may be followed by necrosis.

Sporogenesis and spore structure in Kudoa lunata (Myxosporea, Multivalvulida)

The multivalvulid myxosporean Kudoa lunata Lom, Dyková and Lhotáková, 1983 forms large polysporic trophozoites within the myocytes of scaldfish, Arnoglossus imperialis and A. laterna. The spores arise by the division of generative cells that produce a number of sporogonic cells necessary to complete a sporoblast. The development of some of the sporogonic cells can take place in isolation from other sporoblast cells, as shown by aberrant cases of polar capsule formation. Pansporoblast formation does not exist in Kudoa, at variance with large polysporic trophozoites of other myxosporean genera. The genus Kudoa also includes species with small trophozoites producing just one or two spores without pansporoblasts, as in Sphaerospora. Perhaps this type of sporogenesis was preserved in the species of Kudoa that have large trophozoites. Kudoa spores have a unique type of sporoplasm, comprising an outer cell enveloping an inner one; these differ in their contents of ribosomes and glycogen granules. This type of sporoplasm is reminiscent of the basic unit of all types of myxosporean development, i.e., the primary (vegetative) cell enclosing an inner (generative) cell. The canals for filament discharge extend through the apical spore projections and are of a length unmatched in other myxosporea.

Heterosporis schuberti n.sp., a new microsporidian parasite of aquarium fish.

Heterosporis schuberti n.sp. is described from the myocytes of an ornamental fish, Pseudocrenilabrus multicolor (Cichlidae). An apparently identical species was also found in Ancistrus cirrhosus (Loricariidae). Early meronts - uninucleate or plurinucleate - are perhaps responsible for dissemination of the infection throughout the muscle tissue. Later development of the microsporidian takes place in a structure encased with a thick envelope, for which the name sporophorocyst is proposed. At first, it contains merogony stages. Later, sporogony stages appear, too, which eventually prevail until a voluminous sporophorocyst is packed full with sporophorous vesicles with macrospores and rather rare microspores. Pleistophora anguillarumHoshina, 1951 reveals features similar enough to permit its reassignment to the genus HeterosporisSchubert, 1969.

Kudoa lunata n. sp. (Myxozoa, Myxosporea) and notes on the nature of muscular “cysts” of the genus Kudoa

Summary Kudoa lunata n. sp. has been described from skeletal muscles of 3 species of scaldfish, Arnoglossus imperialis, A. laterna and A. thori . Spores are stellate with 4 blunt, upward lifted tips, with 4 sharp apical projections, their width is 10 (9–11.4) µm, length 5.3 (4.5–6.2) µm. Polar capsules of equal size measure 1.5 × 2.5 µm on the average and have 3 coils of the polar filament. The spindle-shaped trophozoites, 0.5–0.7 × 2–3 mm large, fill centres of muscle fibers and appear as “cysts”. Developing trophozoites are covered solely by their own plasmalemma, adhering regions of the myocyte appear undamaged. Plasmalemma is richly folded to increase the host parasite interface and reveals pinocytotic activity. Histological sections of muscles of 4 other fish hosts infected with undetermined Kudoa species were examined. All these observations result in the conclusion that developing and fully grown trophozoites of Kudoa species located within the myocytes are encased only with their own plasmalemma and elicit no tissue reaction. Such reaction may only set in later.

Hrabyeia xerkophora n.gen. n.sp., a new microsporidian with tailed spores from the oligochaete Nais christinae Kasparzak, 1973.

A new microsporidian, Hrabyeia xerkophora n.g., n.sp., is described from the coelomocytes of the body cavity of a freshwater oligochaete, Nais christinae Kasparzak, 1973 from Czechoslovakia. Infected coelomocytes are turned into xenomas 50 μm in size. Of the incompletely known life cycle, diplokaryotic sporonts developing in close contact with the host cell cytoplasm and diplokaryotic spores were studied. The spores of a Nosema-type have a gnarled caudal appendage encased with and compartmentalized by the exospore.

Light and electron microscopic observations on the swimbladder stages of Sphaerospora renicola, a parasite of carp (Cyprinus carpio).

The developmental cycle of stages ofSphaerospora renicola, proliferating in the walls of the swimbladder in carp fry and responsible for swimbladder inflammation (=SBI stages) is described. The initial stage, a primary cell containing two secondary cells, grows in size while the secondary cells divide and produce two tertiary cells each by endogenous division. After a supposed disintegration of the grown primary cell, the cell triplets are released to repeat the cycle. The cell divisions are asynchronous and the development of the whole formation may be quite irregular. The cytology of these stages is closely reminiscent of the blood stages ofS. renicola and also shares common features with the parasites sporogonic stages. The SBI stages show typical features of myxosporean organisation, i.e., a “cell-within-cell” arrangement in which the primary cell contains secondary cell(s) in membrane-bound vacuoles and many free ribosomes, in the absence of centrioles. Othersalient features of SBI stages are partitions in the nuclei; a small amount of cytoplasm in the early secondary cells; distinct, age-dependent changes in morphology of the nucleus; and atypically shaped Golgi bodies in the cytoplasm or integrated with the nuclear envelope. The cytological features and significance of swimbladder stages are discussed in detail.

Host Cell Hypertrophy Induced by Contact with Trophozoites of Thelohanellus pyriformis (Myxozoa: Myxosporea)

Summary Thelohanellus pyriformis ( Thelohan 1892) from tench (Tinca tinca) gills is redescribed using light and electron microscopy. Trophozoites in form of polysporic plasmodia develop in gill filament arteries. The plasmodia are coated with endothelial cells of the host. One of the cells is enclosed within the plasmodium and becomes greatly hypertrophic without being pervaded by the parasite. The term “contact hypertrophy” is proposed for this phenomenon, which may serve to increase the nutrient flow mediating interface between the host cells and the parasite.

Species of the genus Chloromyxum Mingazzini (Myxozoa: Myxosporea) infecting burbot (Lota lota L.)

Three different species of the genus Chloromyxum Mingazzini were found in burbot (Lota lota L.) collected in south-west Bohemia (Czechoslovakia). Comparison with existing records revealed that one species could be identified as C. pseudomucronatum Kashkovskiy, 1966. Found in the urinary bladder, it had subspherical spores with fine surface ridges and polysporic plasmodia. The two other myxosporea were established as new species: C. lenorae n. sp. was found in the kidney, renal corpuscles, renal tubules and interstitium, and had ellipsoid spores with surface ridges barely perceptible in the light microscope but clearly revealed by transmission electron microscopy. In the polysporic plasmodia, spores developed in pansporoblasts. C. reticulatum n. sp. was found in the gall bladder. It had polysporic plasmodia and spherical spores (average size 8.1 μm in diameter) with a unique surface structures: elevated crests marking off irregular fields which appeared as a reticulum. In five of the fish infected with C. lenorae, bloodstream myxosporean stages of an extrasporogonic cycle were found. Further research is needed to determine whether they are stages of Sphaerospora cristata Shulman, 1962, a species also found in two of the burbot examined, or stages belonging to the Chloromyxum life cycle.

Chloromyxum reticulatum (Myxozoa, Myxosporea) in the liver of burbot (Lota lota L) and its migration to the final site of infection

The coelozoic myxosporean Chloromyxum reticulatum Lom, Dyková and Kepr, 1988 forms large sporogonic plasmodia in the gall bladder of burbot (Lota lota). Different, very small stages of the parasite were detected in the liver parenchyma. Their presence between the hepatocytes provoked no pathological changes and induced no host tissue reaction. They were concentrated beneath the epithelial layer of the proximal parts of the bile ducts, were wedged between the bile duct epithelial cells and also in the lumen. These findings indicate that, contrary to earlier assumptions, myxosporea reach the gall bladder via circulating blood, not directly from the intestine through the common bile duct. Thus the haematogenous spread of early myxosporean stages can be presumed in myxosporeans infecting all sites in the fish body.

Haemogregarina vltavensis n. sp. from perch (Perca fluviatilis) in Czechoslovakia

A new species, Haemogregarina vltavensis n. sp., is described from the blood of perch (Perca fluviatilis) in southwestern Czechoslovakia. Both intra-erythrocytic and free stages interpreted as gametocytes were detected. Only one parasite per erythrocyte was found. It displaces the nucleus and fills most of the volume of the infected host cell. No other developmental stages were discovered.