Light and scanning electron microscopy of Myxobolus porofilus sp. n. (Myxosporea: Myxobolidae) infecting the visceral cavity of Prochilodus lineatus (Pisces: Characiformes: Prochilodontidae) cultivated in Brazil

Myxobolus porofilus sp. n. is described infecting the visceral cavity of Prochilodus lineatus (Valenciennes, 1836) cultivated in S?o Paulo State, Brazil. The plasmodial form of the parasite is 3-5 mm in length and appeared compressed between the wall of the visceral cavity and the pyloric caecum, reposing on this organ. The spores are small (length 5.7 +/- 0.3 microm, width 4.8 +/- 0.2 microm; mean +/- SD) and round to elliptical in frontal view. The valve surfaces are smooth and have sutural folds. The polar capsules are ovoid, small (length 1.6 +/- 0.1 microm, width 1.1 +/- 0.1 microm) and equal in size. The polar filaments have three turns aligned perpendicularly to the longitudinal axis of the capsule. A conspicuous polar filament pore is arranged at the anterior end of the spore. The only reaction observed upon histological analysis was the presence of a capsule of connective tissue surrounding the plasmodia. This is the first report of a myxosporean parasite in the Prochilodontidae.     

Myxobolus intrachondrealis sp. n. (Myxosporea: Myxobolidae), a parasite of the gill cartilage of the common carp, Cyprinus carpio

A species not identifiable with any of the about 23 Myxobolus species recorded from the common carp so far, was detected in the gills of one- and two-summer-old specimens of the common carp ((Cyprinus carpio L.) cultured in pond farms in Hungary. The strictly tissue-specific plasmodia of the parasite were located, surrounded by hyaline cartilage cells, in the chondrous substance of the terminal parts of the gill arches and in the cartilage structure ventrally connecting the gill arches. The spores of the parasite described as Myxobolus intrachondrealis sp. n. developed in globular or ellipsoidal plasmodia measuring 300-600 microm. By their elongated ellipsoidal shape and similarly elongated polar capsules the spores were well distinguishable from the hitherto described Myxobolus species parasitic in the common carp and also from the cartilage-parasitic Myxobolus species of other fishes.     

Intraoligochaete development of Myxobolus intimus (Myxosporea: Myxobolidae), a gill myxosporean of the roach (Rutilus rutilus)

The infection with Myxobolus intimus Zaika, 1965 in the gills of the roach Rutilus rutilus (L.) from Lake Balaton was recorded in 28 out of the 39 fish examined. Developing and mature plasmodia were detected on the gills exclusively in the spring. The Myxobolus intimus infection was found only in 2- to 3-year-old fish. In histological sections, young plasmodia were found in capillaries of the secondary lamellae. More mature, round plasmodia 0.4-0.6 mm in diameter, deformed the respiratory lamellae. The intraoligochaete development of M. intimus was studied in experimentally infected oligochaetes. In two experiments, uninfected Tubifex tubifex Müller and Limnodrilus hoffmeisteri (Claparède) were exposed to mature myxospores of M. intimus. In both experiments, typical triactinospores developed in T. tubifex specimens but no infection was found in L. hoffmeisteri. In semithin sections, developmental stages, pansporocysts and actinospores, were found within the proliferated gut epithelium of T. tubifex. Triactinospores were first released from oligochaetes 37 and 58 days after initial exposure in the two experiments, respectively. Each triactinospore had three pyriform polar capsules and a cylindrical sporoplasm with 32 secondary cells. The spore body joined the 3 caudal projections with a moderately long style.     

Huffmanela paronai sp. n. (Nematoda: Trichosomoididae), a new parasite from the skin of swordfish Xiphias gladius in the Ligurian sea (Western Mediterranean)

A new species of trichosomoidid nematode, Huffmanela paronai sp. n., is established on the basis of its egg morphology and biological characters. The dark-shelled, embryonated eggs of this histozoic parasite occur in masses in the epidermis of the swordfish Xiphias gladius L. (Xiphiidae, Perciformes) from the Ligurian Sea in northern Italy. The eggs are concentrated in groups appearing as black spots in the skin of the fish host, being distributed mainly on the lower part of its body (lower jaw, gill covers, pectoral, anal and caudal fins, lower half of body). The parasite's eggs are characterised mainly by their shape and markedly small size (48-51 x 21-24 microm), an aspinose surface, relatively small polar plugs, and thick egg wall (3 microm). This is the first Huffmanela species reported from fish in Europe.     

The development of Myxobolus pavlovskii (Myxozoa: Myxobolidae) includes an echinactinomyxon-type actinospore

Echinactinomyxon-type actinospores were found in a mixed-species oligochaete culture originating from the Temperate Water Fish Hatchery near Budapest, Hungary. On the basis of DNA sequence analysis, the actinospores were identified as Myxobolus pavlovskii (Akhmerov, 1954), the 18S rDNA sequence from myxospores of which is available in GenBank. Silver carp Hypophthalmichthys molitrix (Valenciennes) fry specimens were successfully infected by cohabitation with the echinactinomyxon-releasing oligochaetes, which confirmed the molecular data congruence. The echinactinomyxons and the myxospores that developed in the gills of exposed fish fry were analysed morphologically and on DNA basis. The infected gill tissue was examined histologically. As typical characters of M. pavlovskii, numerous small plasmodia were observed in the epithelia of gill lamellae. Plasmodia contained thousands of myxospores with polar capsules unequal in size and witl; large intercapsular processes. The 18S rDNA sequence from actinospores and those from myxospores originating from the experimentally infected fish were identical. The oligochaete species releasing actinospores was morphologically determined as Limnodrilus sp. This is the first record of an echinactinomyxon as an alternate stage within the genus Myxobolus.     

Myxozoans infecting the sharptooth catfish, Clarias gariepinus in the Okavango River and Delta, Botswana, including descriptions of two new species, Henneguya samochimensis sp. n. and Myxobolus gariepinus sp. n

During a recent investigation of parasites infecting fishes from the Okavango River and Delta, Botswana (southern Africa) fourteen sharptooth catfish, Clarias gariepinus (Burchell, 1822) (Siluriformes: Clariidae) were examined for the presence of myxozoan infections. Results revealed the presence of two species of the genus Henneguya Thélohan, 1895 and one species of the genus Myxobolus Bütschli, 1882 infecting this fish host. Two of the sampled fish exhibited large plasmodia of Henneguya suprabranchiae Landsberg, 1987 in the cartilage of the accessory breathing organ, another two individuals were infected with H. samochimensis sp. n. plasmodia in the gills and another three individuals revealed an infection with Myxobolus gariepinus sp. n. plasmodia in the ovaries.     

Occurrence of a new microsporidium in the skeletal muscle of the flying fish Cypselurus pinnatibarbatus japonicus (Exocoetidae) from Yakushima, Japan

A new microsporidium was observed in the flying fish Cypselurus pinnatibarbatus japonicus (Franz) (Exocoetidae) from Yakushima, Japan. Visual examination revealed the microsporidium to form white elongate nodules in the host's trunk muscle. Monomorphic spores were ovoid to pyriform in shape, with average dimensions of 4.1 x 2.2 microm and possessing a polar tube describing 13-15 coils. Histological observations showed that each parasite focus of infection was encapsulated by a host-produced fibrous membrane. The presence of sporophorous vesicles was not clearly determined. Ribosomal DNA sequence analyses showed the microsporidium to be discrete from other known fish muscle-infecting species and to be most closely related to a clade comprising the Pleistophoridae and Glugea spp. The parasite is provisionally placed as Microsporidium cypselurus sp. n.     

Fine structure of Henneguya pilosa sp. n. (Myxozoa: Myxosporea), parasite of Serrasalmus altuvei (Characidae), in Brazil

Henneguya pilosa sp. n., a new species of myxosporean from the gill filaments of the white piranha, Serrasalmus altuvei Ramirez, 1965 (Characidae), a freshwater teleost fish collected in the Zoological Garden of the city of Teresina (Piauí), Brazil, is described from light and transmission electron microscope observations. This myxosporean produced small plasmodia (up to 0.2 mm in diameter), each one containing all life-cycle stages of the parasite, including numerous spores. The spores, laterally compressed, averaged 54.2 (52.3-56.0) microm in total length and consisted of two unequal valves adhering together along the suture line and two caudal processes. The spore body measured 21.1 (20.0-23.1) microm in length, 5.9 (5.5-6.3) microm in width, and 2.2 (1.9-2.6) microm in thickness. The two equal ellipsoidal polar capsules of 7.4 (7.1-7.6) microm long and 1.2 (1.0-1.3) microm wide possessed a polar filament with 11-12 (rarely 13) turns. All surfaces of the spores were covered with a tightly adherent complex network of numerous densely ramified granulo-fibrillar masses, the longest measuring 1.5 microm long, observed around the caudal processes. The prevalence of infection was 30%. The taxonomic affinities of this parasite with other of the same genus in freshwater South American fish species are discussed.     

Myxobolus lentisuturalis sp. n. (Myxozoa: Myxobolidae), a new muscle-infecting species from the Prussian carp,Carassius gibelio from China

A new highly pathogenic muscle-infecting species of the genus Myxobolus Bütschli, 1882 is described from the Prussian carp, Carassius gibelio (Bloch, 1782) using spore morphology and SSU rDNA sequence data. Phylogenetic analyses elucidated relationship of the newly described Myxobolus lentisuturalis to other Myxobolus species and supported its position of an independent species.     

Extensive release of an antigen associated with the sporogonic stages of myxobolus cerebralis (Myxozoa: Myxosporea) is detected by a heterologous antibody raised to Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea)

Monoclonal antibody B4 (mAb B4) was previously developed to the myxozoan parasite Tetracapsuloides bryosalmonae Canning, Curry, Feist, Longshaw et Okamura, 1999, the causative agent of proliferative kidney disease of salmonids, Here we describe the reaction of mAb B4 against Myxobolus cerebralis Hofer, 1903, the parasite that causes 'whirling disease' in salmonids. Tissues examined were collected from experimentally infected rainbow trout Oncorhynchus mykiss (Walbaum) and the aquatic oligochaete Tubifex tubifex (O.F. Müller), the two hosts involved in the life cycle of M. cerebralis. Paraffin sections of infected rainbow trout taken at 4 h and 3, 10, 17 and 54 days post-exposure to infective M. cerebralis actinospores were immunohistochemically stained with mAb B4. Longitudinal sections through infected T. tubifex sampled 120 days post-exposure to M. cerebralis myxospores were also examined using this method. The only phase of the M. cerebralis life cycle that expressed the mAb B4 antigen was during sporogenesis in the salmonid host. The immunohistochemical staining demonstrated that the antigen was released into the tissues surrounding the spore and sporogonic stages of the parasite. The localisation of the antigen was diffuse in the fish, suggesting that the possible effect of M. cerebralis infection is extensive through the head tissues and not limited to areas of cartilage destruction as previously thought.     

Occurrence of the microsporidian parasite Nucleospora salmonis in four species of salmonids from the Massif Central of France

Nucleospora salmonis (Hedrick, Groff et Baxa, 1991), an intranuclear microsporidian parasite of marine and freshwater fish, causes diseases mainly in salmonid species. Losses have been reported in stocks of salmonid fish reared in the region of Auvergne (France). The cause of chronic mortalities in the local host species raised in aquaculture and destined for supplementation of the river system Loire-Allier was examined. The presence of N. salmonis was confirmed by PCR and histology in Salmo salar L. previously and in newly investigated salmonid species, Salmo salar, Salmo trutta fario L., Thymallus thymallus (L.) and Salvelinus alpinus (L.), present in European streams. The infection by N. salmonis was consistent in all cases with characteristic symptoms of the disease in deceased or moribund fish. The small subunit ribosomal DNA from N. salmonis was partially sequenced and compared to previously characterised N. salmonis isolates. As a result, a genotype, or clonal entity, was attributed to N. salmonis among Atlantic salmon found along the Northern Atlantic coastal lines and other salmonid species co-inhabiting or co-cultivated in the Auvergne region.     

Differences in viability and reactivity of actinospores of three myxozoan species upon ageing

Little is known about the viability of myxozoan actinospore stages after harvest from laboratory cultures of infected oligochaete worms. The viability and reactivity of actinospores of three myxozoan species was evaluated after short-term storage at 4 degrees C and 12 degrees C. Two methods of determining actinospore viability were compared: differential fluorescent staining and direct microscopic observation of morphological indicators of spore integrity. Spore reactivity was quantified by measuring polar filament discharge rates in a micro-assay with fish mucus substrate and mechanical stimulation by vibration. The age-dependent viability of the three species showed clear differences. Myxobolus cerebralis actinospores had the shortest effective life span whereas Henneguya nuesslini actinospores survived significantly longer. Storage at lower temperatures yielded higher viability in all species. Myxobolus pseudodispar actinospores were significantly robust up to 12 degrees C when assessed by staining, but showed similar viability characteristics as H. nuesslini when analyzed morphologically. Evaluation of spore viability by fluorescent staining correlated with morphological assessment, although fewer viable actinospores were usually detected microscopically. Polar filament discharge activity of morphologically intact actinospores did not significantly decrease until the third day of storage compared to freshly harvested samples. The results indicate that durability and reactivity trends during storage of actinospores differ among myxozoan species.     

Capillostrongyloides Ancistri sp. n. (Nematoda: Capillariidae) a new pathogenic parasite of aquarium fishes in Europe

A new nematode species, Capillostrongyloides ancistri sp. n., is described from the intestine of aquarium-reared catfish Ancistrus dolichopterus Kner in Czechoslovakia. This fish is of South American origin and, therefore, C. ancistri sp. n. has probably been brought into aquaria in Europe from there. The parasite is characterized mainly by the structure of the male caudal end (presence of two large postanal papillae and the cuticular bursa supported by two caudal lobes), the length of a spicule (0.258-0.297 mm), the presence of a non-spiny spicular sheath, shape of the female end, structure of the stichosome (23-30 stichocytes present), and the size of the eggs. The species appears to be highly pathogenic to aquarium-reared Ancistrus dolichopterus, causing death of these fish.     

Moravecnema segonzaci gen. et sp. n. (Nematoda: Cystidicolidae) from Pachycara thermophilum (Zoarcidae), a deep-sea hydrothermal vent fish from the Mid-Atlantic Ridge

A new cystidicolid nematode, Moravecnema segonzaci gen. et sp. n. is described from the intestine of the teleost fish Pachycara thermophilum Geistdoerfer (Zoarcidae) from the hydrothermal sites Logatchev and Snake Pit-Moose of the Mid-Atlantic Ridge, at depths of 3,008; 3,492, and 3,510 m. The new genus Moravecnema is characterised by a dorsoventrally elongated oral opening, rudimentary pseudolabia, and four pairs of precloacal and six pairs of postcloacal caudal papillae in the male. The species has two spicules of unequal length, about 330 and 80 microm long. Males are about 5 mm and females about 5-10 mm long. Eggs have long thin polar filaments. This is the first species of parasitic nematode described from a fish endemic to hydrothermal deep-sea vents.     

Electron microscopic study of a new microsporean Microsporidium epithelialis sp. n. infecting Tubifex sp. (Oligochaeta)

The cytology of a new microsporean parasite Microsporidium epithelialis sp. n. from the intestinal epithelial cells of the freshwater oligochaete Tubifex sp. (Tubificidae) is described. The microsporean occurred together with an actinosporean of the genus Triactinomyxon, which was found between the epithelial cells. The merogonic and sporogonic stages (mature spores included) of the microsporean parasite are monokaryotic. An individual sporophorous vesicle surrounds each spore. The fixed and stained spore has an average dimension of 1.9-2.5 x 0.9-1.2 microm. The spores are oval with a characteristic surface layer, showing ornamentation-like projections, which are in close contact to the exospore. A short polar filament forming three to four coils traverses the polaroplast with two lamellar layers. The ultrastructure and other characteristic features of this microsporean parasite are distinct from those of the microsporean species described so far from oligochaetes.     

Effects of temperature on the in vivo and in vitro multiplication of Trypanosoma danilewskyi Laveran et Mesnil.

Temperature directly affected the in vivo and in vitro multiplication of Trypanosoma danilewskyi Laveran et Mesnil. The parasitemia in experimentally infected goldfish (Carassius auratus L.) increased rapidly at 20 degrees C and reached its peak in 3 to 5 weeks post-infection. The multiplication was slower at 10 degrees C. The parasitemia declined after the peak at 20 degrees C. Lowering of temperature of the infected goldfish from 20 degrees C to 10 degrees C slowed multiplication of the parasite. Similarly, raising of temperature of infected fish from 10 degrees C to 20 degrees C resulted in rapid multiplication of the parasite. These were confirmed in the in vitro studies. It is suggested that lower temperature slows the multiplication of the parasites because T. danilewskyi is a parasite of a warm water host (Carassius auratus gibelio Bloch).     

Morphometrics and seasonal occurrence of metacestodes of Neogryporhynchus cheilancristrotus (Cyclophyllidea: Dilepididae) in the blue bream (Abramis ballerus) from the Oder River (Germany/Poland)

From May 1993 to April 1995, the seasonal occurrence of metacestodes of Neogryporhynchus cheilancristrotus (Wedl, 1855) (Cyclophyllidea: Dilepididae) in its second intermediate host, the blue bream Abramis ballerus (L.) was studied monthly in the Oder River on the borders of Germany and Poland. Based on the parasite specimens found, detailed data on their morphometrics are presented. The metacestodes occurred in the blue bream intestine throughout the year (overall prevalence 27% and intensity 1-56 (mean 4.8) metacestodes per infected fish). Increased prevalences and mean intensities of infection were noted from March to June and November to December indicating that spring, late autumn and early winter are the main periods of new infections.     

Eimeria burdai sp. n. (Apicomplexa: Eimeriidae), a new parasite species from subterranean African silvery mole-rat, Heliophobius argenteocinereus

A new coccidian parasite of the genus Eimeria Schneider, 1875 is described from the subterranean African silvery mole-rat Heliophobius argenteocinereus Peters, 1846. Oocysts of Eimeria burdai sp. n. were subspherical to broadly ellipsoidal 17.8 (16-19) x 14.1 (12-15), with a shape index 1.2 (1.1-1.4). Oocyst wall was bilayered, smooth and colourless, approximately 1.0 thick. Outer layer was significantly thicker than inner one. A micropyle and oocyst residuum were absent. One or two ellipsoidal or spherical polar granules were present. Sporocysts were ellipsoidal, 10.8 (9-12) x 6.2 (5-8) with a shape index 1.7 (1.5-1.9). Sporocyst wall was single-layered, thin, smooth and colourless, with small Stieda body at the pointed end. In freshly sporulated oocysts, spherical sporocyst residuum was composed of small granules enclosed by a thin membrane. Sporozoites were elongate, lying length-wise in the long axis of the sporocyst, partially curled around each other, with single large refractile body located posteriorly. Faintly distinguishable nucleus was in the central part of the sporozoite. This eimerian represents the first coccidian species described from subterranean African silvery mole-rat (Rodentia: Bathyergidae).