Based on light and scanning electron microscopical studies, three adult spirurid nematode species, Camallanus (Zeylanema) ctenopomae Vassiliadès & Petter, 1972, Paracamallanus cyathopharynx (Baylis, 1923) (both Camallanidae) and Spinitectus polli Campana-Rouget, 1961 (Cystidicolidae), are redescribed from specimens collected in fishes of the Okavango River, Botswana: C. (Z.) ctenopomae from Ctenopoma sp. (Anabantidae), P. cyathopharynx from Clarias stappersi Boulenger, C. theodorae Weber (both new hosts, Clariidae) and C. gariepinus (Burchell), as well as S. polli from Synodontis nigromaculatus Boulenger (new host, Mochokidae). Moreover, spirurid larvae of an additional three species were found in fishes from the same locality: Rhabdochona paski Baylis, 1928 fourth-stage larva (Rhabdochonidae) in S. nigromaculatus (Mochokidae), Physalopteridae gen. sp. 1 third-stage larva in C. gariepinus (Clariidae) and Physalopteridae gen. sp. 2 third-stage larva in Serranochromis angusticeps (Boulenger) (Cichlidae), all representing new host and geographical records. Spinitectus zambezensis Boomker, 1993 is considered a junior synonym of S. polli.

Parasitological dissections of fishes from the Okavango River, Botswana, revealed the presence of nematodes of the subgenus Procamallanus (Procamallanus) Baylis, 1923 in five fish species belonging to three different families. Based on light and scanning electron microscopical examinations, they proved to represent one previously known and one new species, i.e. P. (P.) laeviconchus (Wedl, 1861) from Synodontis nigromaculatus Boulenger, S. thamalakanensis Fowler (new host) (both Mochokidae) and Schilbe intermedius Rüppel (new host) (Schilbeidae), and P. (P.) pseudolaeviconchus n. sp. from Clarias stappersi Boulenger and C. theodorae Weber (both Clariidae). Specimens of the new species previously collected from Clarias gariepinus (Burchell) (type-host) in Egypt were also examined. Both of these nematode species are very similar, differing from each other mainly in the shape of the circumoral flange, which is conspicuously lobed in P. laeviconchus and unlobed in P. pseudolaeviconchus. Previously, these two species have been confused in the literature under the name P. laeviconchus. A key to Procamallanus (Procamallanus) spp. parasitising freshwater fishes in Africa, including Madagascar, is provided.

A new branchiurian, Chonopeltis lisikili n. sp., is described from material collected on squeakers (Synodontis spp.) in the Eastern Caprivi, Namibia and Okavango Delta, Botswana. The description is based on investigations of larval stages, ranging from the first instar to sub-adults females with eggs in the uteri, sub-adults and a young male.

Third-stage larvae of the nematode genus Contracaecum Railliet et Henry, 1912 (Contracaecum sp.) were, for the first time, recorded from the abdominal cavity of the threatened endemic freshwater fish Sandelia capensis (Cuvier) in South Africa. The larval morphology indicated that they belong to a species of which the adults are parasitic in fish-eating birds. Although the nematode seems to be a common parasite of S. capensis in the locality under study (prevalence 23%), the low intensity of infection recorded (1 to 4) and the generally known low pathogenicity of Contracaecum larvae in fish indicate that this parasite probably does not represent a danger to the local population of this threatened fish species.

Based on light and scanning electron microscopical studies, eight species (five adult and three larval) of nematodes belonging to the Ascaridida, Oxyurida and Enoplida were collected from fishes of the Okavango River, Botswana, namely Falcaustra similis Moravec et Van As, 2004, Atractidae gen. sp. (only female) (both Cosmocercoidea), Cucullanus sp. (only female) (Seuratoidea), Cithariniella longicaudata sp. n., Synodontisia annulata sp. n. (both Oxyuroidea), Contracaecum sp. third-stage larvae, third-stage larvae of Galeiceps sp. (both Ascaridoidea) and Eustrongylides sp. fourth-stage larvae (Dioctophymatoidea). The new species Citharinella longicaudata (type host Schilbe intermedius Rüppel) is mainly characterised by the shape and size of cephalic papillae and the spicule 108 µm long, and Synodontisia annulata (type host S. intermedius) by the shape of cephalic papillae, body length of gravid females (4.88-5.33 mm) and a short spicule (66 µm long). The female specimen of Cucullanus sp. from Tilapia sparmanni Smith markedly differs from congeners parasitising inland fishes in Africa by the elongate pseudobuccal capsule and by the excretory pore far posterior to the oesophago-intestinal junction; apparently, it belongs to an undescribed species. Galeiceps larvae parasitising fishes are described for the first time. This paper is a continuation of these studies, based on the same nematode collection, now providing results of the systematic evaluation of nematodes of the orders Ascaridida, Oxyurida and Enoplida. Detailed morphological examinations (using both light and scanning electron microscopy) of these materials revealed the presence of several species, including three new taxa of adults and previously undescribed larvae of a little-known anisakid genus. The results are presented herein. MATERIALS AND METHODSA total of 169 specimens belonging to nine fish species of the families Alestidae, Cichlidae, Clariidae, Mochokidae and Schilbeidae were collected in the Okavango River (mainstream in the Shakawe area) in the Panhandle, by gill nets, cast-nets and electro-fishing. Fish were taken live to a nearby field laboratory and maintained unfed in plastic tanks for at least two days to allow the gut to empty. The fish were anaesthetised and killed using MS222 and the internal organs were removed and placed in 1% saline. Nematodes removed from the digestive tract and viscera were fixed in 4% or 10% buffered neutral formalin.For light microscopical examination, the nematodes were cleared gradually in glycerine. Drawings were made with the aid of a Zeiss microscope drawing attachment. Specimens used for scanning electron microscopy (SEM) were post-fixed in 1% osmium tetroxide (in phosphate buffer), dehydrated through a graded ethanol series, critical-point-dried and sputter-coated with gold; they were examined using a JEOL JSM-7401F scanning electron microscope at an accelerating voltage of 4 kV (GB low mode). All measurements are in micrometres unless otherwise indicated. Only small numbers of the available s...

Abstract. 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.

Abstract. Fieldwork was conducted in 1998 and 1999 in the Okavango River and Delta and a total of 275 fishes representing 31 species were examined for the presence of myxosporean parasites. A total of seven myxosporeans of the genus Myxobolus Bütschli, 1882 were found infecting the fishes. Two new species namely Myxobolus etsatsaensis sp. n. from Barbus thamalakanensis Fowler, 1935 and M. paludinosus sp. n. from Barbus paludinosus Peters, 1852 are described. Myxobolus africanus Fomena, Bouix et Birgi, 1985, M. camerounensis Fomena, Marqués et Bouix, 1993, M. hydrocyni Kostoïngue et Toguebaye, 1994, M. nyongana (Fomena, Bouix et Birgi, 1985 and M. tilapiae Abolarin, 1974 are recorded for the first time in Botswana and descriptions of these species are provided.Myxosporean research in Africa dates back to the late 19 th century with Gurley (1893) being one of the earliest authors referring to the continent. The African continent boasts over a 100 myxosporean species from freshwater, brackish and marine fishes of which 84 infect primarily freshwater fishes (Fomena and Bouix 1997) and this number is continuously growing. When comparing the known African myxosporeans to the more than 1,300 species described worldwide, it is evident that for a huge continent with such high fish diversity, a large gap exists in the knowledge on the occurrence and distribution of these parasites.In southern Africa little research has been conducted on myxosporean parasites of fish, with only a few publications appearing largely on marine myxosporeans from South Africa such as Fantham (1919Fantham ( , 1930, Gilchrist (1924), Paperna et al. (1987) and Ali (2000). The only record ever of a freshwater myxosporean from Botswana is that of Peters (1971), commenting on Boulenger (1911) who published a brief note on an anabantid showing a mouth-brooding habit from the Okavango River. According to Peters (1971), Boulenger commented the following: "On examining a female, about 5 ins. long, I found seven or eight eggs about one line in diameter, closely packed on each side in a cavity behind the gills, entirely covered by operculum". While conducting comparative studies on the ethology of African Anabantidae, Peters (1971) examined the rounded bodies, which did look like eggs, and discovered that they were in fact mature plasmodia from a myxosporean infection. Now, 30 years later, the results of the first investigation into myxosporean parasites infecting fishes in the Okavango River and Delta are presented. Over a period of two years (1998 and 1999) a total of 275 fishes from the Okavango Delta, representing 31 species and 9 families were examined for the presence of myxosporean parasites. This paper reports on the occurrence of seven myxosporeans of the genus Myxobolus Bütschli, 1882 found infecting eight different host fish species in the Okavango River and Delta, Botswana. MATERIALS AND METHODSFieldwork was conducted in the Okavango River and Delta in Botswana during June and July in both 1998 and 1999. Fishes were collected using hand nets,...

Abstract. Current records of marine myxozoans from the coast of Africa are limited to the descriptions of 52 species from mostly Senegal, with a few from Tunisia and southern Africa. Between 1998 and 2000 several intertidal fishes from the southern Cape coast of South Africa were examined for the presence of myxozoan infections. Three new species, Ceratomyxa dehoopi sp. n., C. cottoidii sp. n. and C. honckenii sp. n. were identified from the gall bladders of Clinus superciliosus L., C. cottoides Valenciennes and Amblyrhynchotes honckenii (Bloch), respectively. A fourth new species Henneguya clini sp. n. was also identified from the gills and gill arches of C. superciliosus.Very little is known about the distribution and diversity of marine myxozoans along Africa's coastline. Research on these parasites is restricted to the description of 52 species from the entire extent of the African coastline, the majority of which were described from Senegal. Early records of myxozoan infections in African marine fishes appeared from southern Africa between 1919 . Fantham (1919, 1930 recorded several myxozoan species from the bile of a number of intertidal fishes along the Cape south coast. Gilchrist (1924) described Chloromyxum thyrsites Gilchrist, 1924 from the muscles of Cape Sea fish, or "snoek", which is a species well-known around the world today as the notorious Kudoa thyrsites (Gilchrist, 1924). Subsequent to Gilchrist's (1924) description, Davies and Beyers (1947) recorded the presence of K. thyrsites in some of the South African trawled fishes and during the 1970s Dubina and Isakov (1976), Gaevskaya and Kovaleva (1979) as well as Schulman et al. (1979) described several new myxozoan species from deep sea fish off the coast of southern Africa.After these initial myxozoan publications from southern Africa, approximately 15 years passed before a number of species descriptions started to appear from the North-West coast of Africa (Bahri et al. 1995, Bahri and Marqués 1996, Kpatcha et al. 1996a, b, 1997). Subsequent to these publications Ali (2000) described Ortholinea basma Ali, 2000 from the gall bladder of the agile klipfish Clinus agilis, from the West coast of South Africa. This paper represents the first publication on the occurrence of myxozoans infecting intertidal fishes from the De Hoop Nature Reserve along the south coast of South Africa. Three new species of the genus Ceratomyxa Thélohan, 1892, are described from the gall bladders of Clinus superciliosus L., C. cottoides Valenciennes and Amblyrhynchotes honckenii (Bloch), respectively. A fourth new species from the genus Henneguya Thélohan, 1892 is described from the gills and gill arches of C. superciliosus. MATERIALS AND METHODSA total of 14 Amblyrhynchotes honckenii, 44 Clinus cottoides and 131 C. superciliosus were collected on several fieldtrips to the De Hoop Nature Reserve and Jeffrey's Bay, both of which are situated along the south coast of South Africa. Fishes were collected from intertidal rock pools using small hand nets and hand lines. Captu...