Thelohanellus njinei sp nov and T lagdoensis sp nov, Myxosporidia (Myxozoa: Myxosporea) parasites of Schilbeidae and Citharinidae fishes in Cameroon (central Africa)

The study of Myxosporidia infecting Schilbe mystus (Linné, 1758) (Schilbeidae) and Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Citharinidae) from the Sanaga and Bénoué basins revealed the presence of two new species of the genus Thelohanellus kudo, 1993. These species are Thelohanellus njinei sp. nov. and Thelohanellus lagdoensis sp. nov., found in the gut of Schilbe mystus and Citharinus citharus respectively. New data are also given on the diagnosis of Thelohanellus citharini, a species previously described in Chad.     

Henneguya cartilaginis n. sp. (Myxozoa: Myxosporea) in the head cartilage of masu salmon Oncorhynchus masou masou

Henneguya cartilaginis n. sp. (Myxozoa: Myxosporea) is described from wild masu salmon Oncorhynchus masou masou in Hokkaido, Japan. H. cartilaginis n. sp. produced white cysts, up to 3mm in size, in the head of masu salmon. Infected fish exhibited cranial protrusion due to the cysts. Spores (11.4 × 8.6μm) of H. cartilaginis n. sp. were egg-shaped with the posterior end more pointed and possessed two caudal appendages (34.2μm average length). Histological observations revealed that large plasmodia possessing fine fibrous pseudopodia on the surface developed in the head cartilage. H. cartilaginis n. sp. resembles H. cerebralis, which was described from the cranial cartilage of Kosogol grayling Thymallus nigrescens in Mongolia. However, they were distinguishable by spore morphology. Molecular analysis of the 18S rDNA sequences indicated that H. cartilaginis n. sp. was most closely related to Henneguya zschokkei, H. nuesslini and H. salminicola of salmonid fish, with genetic similarities of 95.3%, 95.1% and 93.9%, respectively. Based on these differences in spore morphology, molecular data, the site of infection and geographical distribution, the present species is considered to be a new species.     

Microcostatus schoemanii sp. nov., M. cholnokyi sp. nov. and M. angloensis sp. nov. three new terrestrial diatoms (Bacillariophyceae) from South Africa

The terrestrial diatom Microcostatus schoemanii sp. nov. is described from dry soils of the Faan Meintjies Nature Reserve (North‐West Province, South Africa). Microcostatus cholnokyi sp. nov. and Microcostatus angloensis sp. nov. are described from sandy soils at a colliery near the town of Kriel (Mpumalanga Province, South Africa). The morphology of these taxa is examined using both light and scanning electron microscopy and new taxa are compared with similar species. In M. schoemanii the density of the striae combined with the valve outline and the distance between the central raphe endings are the main distinguishing morphological features. M. cholnokyi is differentiated by the presence of a conopeum and the distinct structure of the microcostae. M. angloensis is similar to M. schoemanii but differentiated by the shape of the cell and the apices, the angle of striation and the distance in between the proximal raphe endings.     

Myxobolus desaequalis n. sp. (Myxozoa,Myxosporea), parasite of the Amazonian freshwater fish,Apteronotus albifrons (Teleostei,Apteronotidae)

Myxobolus desaequalis n. sp. is described from the gill lamellae of the freshwater fish Apteronotus albifrons, collected in the Amazon River, near the city of Salvaterra, Brazil. Large spherical plasmodia filled with disporic pansporoblasts and spores were observed. Ellipsoidal to pyriform spores are 18.3 microm length x 11.2 microm width x 4.4 microm thickness. The anterior end of the spores contain two extremely unequal pyriform polar capsules measuring: (larger): 11.2 microm length, 4.9 microm width, and an isofilar polar filament with 11 to 12 turns obliquely to the longitudinal axis; (smaller): 4.6 microm length, 2.8 microm width, and an isofilar polar filament with 4 to 5 turns, obliquely to the longitudinal axis.     

An ultrastructural and histopathological study of Henneguya pellucida n. sp. (Myxosporea: Myxobolidae) infecting Piaractus mesopotamicus (Characidae) cultivated in Brazil

During a study of myxosporean parasites of cultivated freshwater fish, a new myxosporean species, Henneguya pellucida n. sp., was discovered. Of the 120 Piaractus mesopotamicus sampled, only 10 specimens (8.3%) were infected. Yellow, round plasmodia measuring 0.5-3 mm were found in the serous membrane of the visceral cavity and in the tunica externa of the swim bladder. Sporogenesis was asynchronous, with the earliest developmental stages aligned prevailingly along the endoplasmic periphery and mature spores in the central zone. The mature spores were pear shaped (total length: 33.3 +/- 1.5 microm, mean +/- SD; width: 4.1 +/- 0.4 microm; body length: 11.4 +/- 0.3 microm; caudal process length: 24.1 +/- 1.5 microm). The polar capsules were elongated (length: 4.0 +/- 0.4 microm; width: 1.6 +/- 0.2 microm). The development of the parasite in the swim bladder produced thickening of the tunica externa and a granulomatous reaction. There was no correlation between the prevalence of the parasite and the chemical and physical characteristics of the water. Infection was recorded only in juvenile specimens ranging in size from 9.5 to 20 cm.     

Three new species of Myxosporidia (Myxozoa: Myxosporea) parasites of Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Citharinidae) in Chad (Central Africa)

The study of Citharinus citharus (Geoffroy Saint-Hilaire, 1809) (Teleost, Citharinidae) captured in the Chari river in Chad revealed the presence of three new myxosporidian which are described in the present paper: Thelohanellus taguii sp. nov., a systematic parasite; Myxobolus mbailaoi sp. nov., which affects operculum, skin and intestine, Myxobolus charii sp. nov., a parasite of the skin.     

Myxobolus insignis sp. n. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the Amazonian teleost fish Semaprochilodus insignis (Osteichthyes, Prochilodontidae)

A new myxosporean species is described from the fish Semaprochilodus insignis captured from the Amazon River, near Manaus. Myxobolus insignis sp. n. was located in the gills of the host forming plasmodia inside the secondary gill lamellae. The spores had a thick wall (1.5-2 microm) all around their body, and the valves were symmetrical and smooth. The spores were a little longer than wide, with rounded extremities, in frontal view, and oval in lateral view. They were 14.5 (14-15) microm long by 11.3 (11-12) microm wide and 7.8 (7-8) microm thick. Some spores showed the presence of a triangular thickening of the internal face of the wall near the posterior end of the polar capsules. This thickening could occur in one of the sides of the spore or in both sides. The polar capsules were large and equal in size surpassing the midlength of the spore. They were oval with the posterior extremity rounded, and converging anteriorly with tapered ends. They were 7.6 (7-8) microm long by 4.2 (3-5) microm wide, and the polar filament formed 6 coils slightly obliquely to the axis of the polar capsule. An intercapsular appendix was present. There was no mucous envelope or distinct iodinophilous vacuole.     

Myxobolus absonus sp. n. (Myxozoa: Myxosporea) parasitizing pimelodus maculatus (siluriformes: Pimelodidae), a South American freshwater fish

A new myxoporean species is described from a freshwater fish in Brazil. Myxobolus absonus sp. n. was found infecting Pimelodus maculatus captured in the river Piracicaba, State of S?o Paulo, Brazil. Cysts were found free in the opercular cavity. The spores are large (length--15.7 +/- 1.5 microns, width--10.2 +/- 0.7 microns; mean +/- S.D.) and oval in shape, with the anterior end slightly pointed. The spore valves are relatively thin, smooth, and asymmetrical in a frontal view. The polar capsules are pyriform in shape, and unequal in size; the largest are 6.4 +/- 0.7 microns long and 3.6 +/- 0.5 microns wide, while the smallest are 4.2 +/- 0.6 microns long and 2.5 +/- 0.5 microns wide.     

Revision of Myxobolus heterosporus Baker, 1963 (syn. Myxosoma Heterospora) (Myxozoa: Myxosporea) in African records

There is uncertainty regarding the validity of Myxobolus heterosporus Baker, 1963. The present study revises the taxonomy, using specimens isolated from plasmodia situated in the infected cornea of Oreochromis aureus, O. niloticus or Tilapia zillii inhabiting the River Nile, Egypt. In addition, histological effects of the parasite on the infected tissue were examined. The spores of M. heterosporus had a variety of shapes expressing remarkable heteromorphism. Five main Myxobolus-like spore types and tailed-spores were found. All forms were photographed, measured, sketched and described. Light and electron microscopy supported that spores of a Myxobolus-like morphology co-existed with so-called tailed-spores in one plasmodium. Some transitional stages from Myxobolus-like spore types to tailed-spores were observed. Therefore, some tailed-spores may be simply heteromorphs of Myxobolus.     

Myxobolus cuneus n. sp. (Myxosporea) infecting the connective tissue of Piaractus mesopotamicus (Pisces: Characidae) in Brazil: histopathology and ultrastructure

The characteristics of Myxobolus cuneus n. sp. and its relationship to the host Piaractus mesopotamicus are described based on light and electron microscopy and histological observations. Polysporic plasmodia measuring 20 microm to 2.1 mm in size were found in 63.3 % of the P. mesopotamicus examined. The parasite was found in the gall bladder, urinary bladder, gills, spleen, fins, head surface, liver and heart. Generative cells and disporoblastic pansporoblasts occurred along the periphery of the plasmodia, and mature spores were found in the internal region. The mature spores had a pear shaped body in frontal view, with a total length of 10.0 +/- 0.6 microm and a width of 5.1 +/- 0.3 microm (mean +/- SD). The spore wall was smooth with sutural folds. The polar capsules were elongated, were pear shaped, and equal in size (length 5.7 +/- 03 microm; width 1.7 +/- 0.2 microm), with the anterior ends close to each other. The polar filaments were tightly coiled in 8-9 turns perpendicular to the axis of the capsule. The plasmodia were always found in connective tissue (wall of the arterioles of the gill filaments, serous capsule of the gall bladder, middle layer and subepithelial connective tissue of the urinary bladder, connective tissue between the rays of the fins, subcutaneous tissue of the head surface and fibrous capsule spleen). The parasite caused important damage in the gills, where development occurred in the wall of gill filament arterioles; a mild macrophage infiltrate was also observed. In advanced developmental stages, the plasmodia caused deformation of the arteriole structure, with a reduction and, in some cases, obstruction of the lumen. The parasite was found throughout the period studied and its prevalence was unaffected by host size, season or water properties.     

Myxobolus goensis n. sp. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the gills of Mugil cephalus (Osteichthyes, Mugilidae) from Goa, India

Two species of Myxobolus are reported from the gills of Mugil cephalus collected at Goa, India: M. goensis n. sp. and M. parvus Shulman, 1962. Myxobolus goensis n. sp. forms digitiform or rounded plasmodia between the gill rakers. Their spores are oval in frontal view, with tapered anterior extremity, and lemon-shaped in lateral view, measuring 9.7 (9.5-10.5) microm in length, 6.6 (6-7.5) microm in width, and 5.2 (5-6) microm in thickness. The polar capsules are pyriform and unequal in size. The larger ones are 5.3 (4.5-6) microm long and 2.4 (2-3) microm wide; the smaller ones are 2.4 (2-3) microm long and 1.8 (1.5-2) microm wide. The polar filament forms five turns aligned perpendicularly to the longitudinal axis of the larger polar capsules. Within the smaller polar capsules the polar filament is difficult to observe and, apparently, forms three coils. The spores are distinctly different from other Myxobolus species infecting M. cephalus and other Mugil spp. Furthermore, the present material is also different from 204 Myxobolus species presenting differently sized polar capsules, representing nearly all the known species with this characteristic. The fact that only the M. cephalus specimens were infected among a sample of 206 fish specimens, comprising 27 different species, strongly suggests that this parasite is specific to M. cephalus.     

Diospyros korupensis sp. nov. and Diospyros onanae sp. nov. (Ebenaceae) from Cameroon

Diospyros korupensis Gosline is described as a new species endemic to the Korup National Park in Cameroon and neighbouring areas on the slopes of Mt Cameroon. Diospyros onanae Gosline is described as a new species from the South and Southwest Regions of Cameroon allied to the poorly known D. soyauxii Gürke & K. Schum. ex. Gürke.     

Ultrastructural aspects of the myxosporean Henneguya astyanax n. sp. (Myxozoa: Myxobolidae), a parasite of the Amazonian teleost Astyanax keithi (Characidae)

This study reports light and electron microscopical aspects of a myxosporean found in the gills of the freshwater teleost Astyanax keithi Géry, Planquete & Le Bail, 1996 (family Characidae), collected from the estuarine region of the Amazon River, near Belém, Brazil. The prevalence of infection was 23%. In interlamellar spaces of the gills, ellipsoidal whitish cyst-like plasmodia structures were present, which contained spores. The spores had a spermatozoa-like appearance (47.8 +/- 0.71 microm in total length) with a fusiform body (15.2 +/- 0.77 pm in length, 5.7 +/- 0.71 microm in width and 4.2 +/- 0.31 microm in thickness), and each of the 2 valves presented a tapering tail (32.6 +/- 1.11 microm in length). The valves surrounded a binucleate sporoplasm cell and 2 polar capsules (5.0 +/- 0.13 microm in length, 1.5 +/- 0.07 microm in width) that contained 8 to 9 coils of the polar filament. In the sporoplasm, several unique sporoplasmosomes were visible. A synoptic table of spore measurements of known Brazilian Henneguya species is presented. The spores differed from those of previously described species. Based on spore morphology, it is concluded that this species belongs to the family Myxobolidae, genus Henneguya, and that it constitutes a new species: H. astyanax n. sp.     

F-actin and beta-tubulin localization in the myxospore stinging apparatus of Myxobolus pseudodispar Gorbunova, 1936 (Myxozoa, Myxosporea)

To understand the discharge mechanism of Myxozoan polar capsule (cnida) it is necessary to verify the role of major cytoskeletal proteins in the process. With this aim F-actin and beta-tubulin localization in spores of myxosporean developmental phase (in myxospores) of Myxobolus pseudodispar Gorbunova, 1936 has been studied under confocal scanning laser microscope using phalloidin fluorescent staining of F-actin and indirect anti-beta-tubulin immunostaining. F-actin has been detected in walls of the stinging tube invaginated into the polar capsule of myxospore. The fact suggests the contractile proteins involvement in the process of myxozoan polar capsule extrusion. In addition, the cytoplasm of amoeboid sporoplasm inside the spore cavity is stained by phalloidin. A polar cap with strong beta-tubulin immunoreacton is observed at the front pole of fully mature myxospore above the outlets of the polar capsule discharge channels. The role of the beta-tubulin cap is supposed to be similar to that of the cnidarian cnidocil made of microtubules. The weaker beta-tubulin immunoreactivity has been found in stinging tubes, in polar capsule walls as well as in the suture line of spore walls and in the cytoplasm of amoeboid sporoplasm. The involvement of cytoskeletal proteins in the process of polar capsule extrusion is discussed. A hypothesis on the myxozoan polar capsule discharge mechanism is suggested. The mechanism of myxozoan cnida discharge is compared with that of cnidaria.     

Histology, ultrastructure and prevalence of Henneguya piaractus (Myxosporea) infecting the gills of Piaractus mesopotamicus (Characidae) cultivated in Brazil

The histopathological and ultrastructural characteristics of Henneguya piaractus, a parasite of the gill lamellae of Piaractus mesopotamicus, are reported here. Histological analysis showed that the plasmodia were of the intralamellar type. The development of the plasmodia resulted in marked dilatation of the infected lamellae, with the neighbouring lamellae being displaced laterally. Discreet epithelial hyperplasia was observed, but there was no inflammatory reaction. Ultrastructural analysis showed that the plasmodium had a single thin wall that was in direct contact with the host cells. Pinocytic canals and points of phagocytosis were observed in the wall. The prevalence of the parasite varied according to host size, with the lowest prevalence occurring in hosts up to 10 cm long.     

Morphological,ultrastructural and phylogenetic analyses of Myxobolus hilarii n. sp. (Myxozoa,Myxosporea), a renal parasite of farmed Brycon hilarii in Brazil

Myxobolus hilarii n. sp. was described, based on morphology, histology, ultrastructure and 18S rDNA sequencing, infecting the kidney of Brycon hilarii (Valenciennes 1850) (Characiformes: Bryconidae) taken from fish farms in the state of São Paulo, Brazil. Thirteen specimens of B. hilarii were examined and 100% had round, white plasmodia in the kidney. The mature myxospores were rounded, measuring 11.5 ± 0.8 (9.8–13.4) μm in length, 11.0 ± 0.7 (9.7–12.4) μm in width and 7.6 ± 1.0 (6.7–9.0) μm in thickness. Polar capsules were elongated and of equal size, with 6.5 ± 0.4 (6.0–7.2) μm in length and 4.0 ± 0.2 (3.6–5.3) μm in width and their polar filaments had 5 to 7 coils. Histological analysis revealed plasmodial development in the renal tubules, causing compression and deformation of adjacent tissues and destruction of renal tubule cells. Ultrastructural analysis showed direct contact between the plasmodial wall and the host tissue and asynchronous plasmodial development. The phylogenetic analysis of South American myxobolids, based on 18S rDNA sequencing, showed the myxosporeans grouping into two main clades. M. hilarii n. sp. appears as sister species of Myxobolus piraputangae.     

Two new species of Myxozoa, Myxobolus inaequus sp. n. and Henneguya theca sp. n. from the brain of a South American knife fish, Eigemannia virescens (V.)

Two new species of Myxozoa from the brain of the green knife fish Eigemannia virescens are described: Myxobolus inaequus sp. n. has an unusually large spore body and extremely unequal polar capsules, and Henneguya theca sp. n. has an attenuated spore encased in a sheath not previously described in other Myxozoa . Only spores of the two species were observed, and infections caused no obvious pathological changes in the brain.     

Two New Species of Myxozoa, Myxobolus inaequus sp. n. and Henneguya theca sp. n. from the Brain of a South American Knife Fish, Eigemannia virescens (V.)

Two new species of Myxozoa from the brain of the green knife fish Eigemannia virescens are described: Myxobolus inaequus sp. n. has an unusually large spore body and extremely unequal polar capsules, and Henneguya theca sp. n. has an attenuated spore encased in a sheath not previously described in other Myxozoa. Only spores of the two species were observed, and infections caused no obvious pathological changes in the brain.