Dujardinascaris malapteruri (Baylis, 1923) Baylis, 1947

Moravec, František & Jirků, Miloslav, 2017, Some nematodes from freshwater fishes in central Africa, Folia Parasitologica (033) 64, pp. 1-39 : 29

Dujardinascaris malapteruri (Baylis, 1923) Baylis, 1947

Figs. 24 , 25

Syns.: Dujardinia malapteruri Baylis, 1923 ; Dujardinascaris graberi Troncy, 1969

Description. Female (based on 2 gravid specimens). Length of body 35.7–45.9 mm, maximum width 816–952. Cuticle finely transversely striated ( Fig. 25F ). Lips and interlabia 129–150 and 75 long, respectively ( Figs. 24B,C , 25A–E ). Length of oesophagus 3.4–3.7 mm, maximum width 136–150, representing 8–10% of body length; ventriculus 163–204 long, 122–163 wide; intestinal caecum 2.0– 2.2 mm long, 190–218 wide ( Fig. 24A ). Nerve ring and excretory pore 625–707 and 653–694 from anterior extremity, respectively. Vulva 14.6–15.6 mm from anterior end, situated at 43–44% of body length; anterior vulval lip slightly elevated. Vagina directed posteriorly from vulva. Eggs almost spherical, thin-walled, with smooth surface, 45–54 in diameter; content of eggs uncleaved ( Fig. 24E ). Tail conical, 585–612 long, with sharply pointed tip; phasmids indistinct ( Figs. 24D , 25G ).

Host: Malapterurus monsembeensis Roberts ( Malapteruridae , Siluriformes ).

Site of infection: Stomach.

Locality: Lower Congo River, left bank near Pioka, 04°54'25''N; 14°23'53''E, Democratic Republic of the Congo (collected 7 July 2008).

Prevalence and intensity: 1 fish infected/15 fish examined; 2 nematodes.

Deposition of voucher specimens: IPCAS N-1135.

Remarks. Because no males were available, the species identification is mainly based on the absence of rows of denticles on lips, small size of eggs and the fact that the fish host belongs to the same genus as that from which this species was originally described.

Baylis (1923b) was the first to describe D. malapteruri from Malapterurus electricus (Gmelin) in Khartoum, Sudan; this species was also reported from the same host species and locality by Khalil (1969). Later Sprent (1990) redescribed D. malapteruri based on Baylis‘ type specimens and those collected from M. electricus in Gabon. According to him, Dujardinascaris graberi , described from M. electricus in Chad ( Troncy 1969), is a junior synonym of D. malapteruri .

Vassiliadẻs and Troncy (1974) reported D. graberi (= D. malapteruri ) also from Heterotis niloticus (Cuvier) ( Osteoglossiformes : Arapaimidae ) and Mormyrops engystoma Boulenger ( Osteoglossiformes : Mormyridae ) in Chad, but Sprent (1990) has mentioned that the identity of these nematodes with D. malapteruri is uncertain. Probably these nematodes belonged to Multicaecum heterotis Petter, Vassiliad ẻs et Marchande, 1979 and Dujardinascaris mormyropsis Moravec et Jirkû, 2014 , respectively ( Moravec and Jirkû 2014a).

Dujardinascaris malapteruri has not previously been examined by SEM. The present SEM study shows that, in contrast to the recently described D. mormyropsis or some other congeneric species parasitising crocodiles, e.g. D. helicina (Molin, 1860) (see Moravec 2001), dentigerous ridges on lips of D. malapteruri are actually absent ( Fig. 25B ).

Most species of Dujardinascaris are parasites of crocodilians ( Mozgovoy 1953, Sprent 1977, Hartwich 2009), whereas adults of only two species, D. malapteruri and D. mormyropsis , are known from freshwater fishes in Africa ( Moravec and Jirkû 2014a). The latter species, a parasite of mormyrids, differs from D. malapteruri mainly in the presence of dentigerous ridges on lips, absence of caudal alae in the cloacal region, morphology of the gubernaculum and larger eggs (60–90 µm × 52–78 µm). As mentioned above, D. malapteruri was previously reported from the Sudan, Gabon and Chad; the finding of this species from M. monsembeensis in the Democratic Republic of the Congo represents new host and geographical records.

Figures

Fig. 24. Dujardinascaris malapteruri (Baylis, 1923) from Malapterurus monsembeensis Roberts, female. A – anterior end of body, lateral view; B, C – cephalic end, dorsal and subventral views, respectively; D – tail, lateral view; E – egg.

Fig. 25. Dujardinascaris malapteruri (Baylis, 1923) from Malapterurus monsembeensis Roberts, scanning electron micrographs of female. A – cephalic end, apical view; B – inner side of dorsal lip, subterminal view; C – dorsal lip, dorsal view; D – subventral lip, subventral view; E – cephalic end, ventral view; F – detail of body cuticle; G – tail, sublateral view. Abbreviations: b – double labial papilla; c – single labial papilla; d – dorsal lip; i – interlabium; s – subventral lip.