Gendria longispiculata, Moravec & Jirků, 2017

Moravec, František & Jirků, Miloslav, 2017, Some nematodes from freshwater fishes in central Africa, Folia Parasitologica (033) 64, pp. 1-39 : 12-17

Gendria longispiculata sp. n.

Figs. 10–12

ZooBank number for species:

urn:lsid:zoobank.org:act:1C60406E-BD12-476D-8CD7-F5991C905919

Description male (1 specimen, holotype). Medium-sized, whitish nematode with bulbous cephalic region and smooth cuticle. Length of body 16.3 mm, maximum width 422. Cephalic vesicle well developed, 123 long and 141 wide ( Figs. 10A,B , 11A,H ). Oral aperture almost circular, surrounded by 6 (2 dorsolateral, 2 ventrolateral and 2 lateral) slightly outlined cuticular lobes giving hexagonal appearance of mouth in apical view; these lip-like formations, 15 high, continuous posteriorly with cephalic vesicle. Oral aperture surrounded by 8 submedian cephalic papillae arranged in 2 circles, each formed by 4 papillae, and 2 small lateral papilla-like amphids; papillae of inner circle distinctly smaller than those of outer circle ( Figs. 10D , 11A–C ). Anterior edge of proper oral aperture provided internally with row of numerous small denticles visible only in SEM ( Figs. 10D , 11D,E ). Mouth depressed, buccal cavity with 3 conical teeth, 1 large dorsal (12 high) and 2 smaller ventrolateral (9 high) ( Fig. 10A–D ). Oesophagus 558 long, at level of nerve ring subdivided into anterior muscular portion and posterior muscular-glandular portion opening into intestine through large valve; anterior half of anterior portion of oesophagus somewhat expanded, 159 long and 78 wide; posterior portion of oesophagus expanding posteriorly, 261 long and 102 wide; minimum width of oesophagus 48 ( Fig. 10A,B ). Nerve ring and small deirids 286 and 798, respectively, from anterior end of body ( Figs. 10A , 11F ). Excretory pore located short distance posterior to level of deirids, at 884 from anterior extremity. Posterior end of body ventrally curved, provided with distinct ventral sucker located 884 anterior to cloacal opening and with many inconspicuous, paired oblique subventral muscle bands in region between sucker and cloaca ( Figs. 10E , 11G , 12A ). Testis reaching anteriorly to 2.4 mm below posterior end of oesophagus; seminal vesicle posterior to level of pseudosucker. Spicules alate, equal, 1,224 long; withdrawn spicules reach approximately from anterior margin of pseudosucker to cloacal opening ( Fig. 10E ). Gubernaculum of complex structure, 99 long, with proximal tip ventrally curved in lateral view ( Fig. 10F ). Genital papillae very small, difficult to observe ( Fig. 12B ). Preanal papillae: 6 subventral pairs and 1 median ventral papilla located short distance anterior to cloaca. Postanal papillae: 6 pairs (4 subventral and 2 lateral) ( Figs. 10E–G , 12C,D ). Tail conical, pointed, 150 long, forming short posterior narrowed portion 30 long and 15 wide ( Figs. 10E–G , 11G , 12A,C ).

Female. Not known.

Type host: Schilbe grenfelli (Boulenger) ( Schilbeidae , Siluriformes).

Site of infection: Intestine.

Type locality: Lower Congo River , right bank near Bulu, Democratic Republic of the Congo, 05°01'30''N; 14°00'25''E (collected 11 July 2008) .

Prevalence and intensity: 1 nematode found in one of two specimens of S. grenfelli examined.

Deposition of type specimen: IPCAS N-1132 (body ends of holotype mounted on SEM stub, middle part of body in a vial) .

Etymology: The name longispiculata relates to the most characteristic feature of this nematode species, i.e. the presence of unusually long spicules as compared with congeners.

Remarks. Three quimperiid genera, Buckleynema Ali et Singh, 1954 , Chabaudus Inglis et Ogden, 1965 and Gendria Baylis, 1930 , include morphologically very similar species parasitising freshwater fishes and amphibians in Africa and South Asia. The only intergeneric features are some details in the cephalic structure (Ivashkin and Khromova 1976, Anderson et al. 2009). Whereas the buccal cavity of Buckleynema is allegedly armed with six teeth, that of Chabaudus or Gendria possesses three teeth; the oral aperture of Chabaudus is surrounded by three bilobed lip-like formations giving it a hexagonal appearance of mouth in apical view, in contrast to allegedly circular oral aperture in Gendria . However, it is necessary to remark that these structures are very difficult to observe in LM and can be properly studied only by SEM. However, none of the species of Buckleynema and Gendria has so far been examined using SEM and the only species of Chabaudus studied by this method is C. leberrei (Bain et Philippon, 1969) , a parasite of African frogs and toads ( Jackson et al. 2001). Most species of these three genera were inadequately described and their cephalic ends were rarely studied in apical view under the LM.

Of ten nominal species of Gendria (see Baylis 1930, Vassiliadẻs and Chevalier 1973, Ivashkin and Khromova 1976, Baker 1987, Sood 1990), most have been described from amphibians in Africa and South Asia, whereas only two are known to parasitise freshwater fishes in Africa: G. tilapiae Baylis, 1930 from Sarotherodon galilaeus (Linnaeus) (Cichlidae) in Mali ( Baylis 1930, Chabaud 1956) and G. polypteri Vassiliadẻs et Chevalier, 1973 from Polypterus senegalus Cuvier and Erpetoichthys calabaricus Smith (both Polypteridae ) in Senegal (Vassiliadès and Chevalier 1973, Vassiliadẻs 1976) and Nigeria (fish imported into the Czech Republic), respectively ( Řehulková et al. 2005).

To date, six species of Chabaudus are known, four of which occur in Africa: C. chabaudi Inglis et Ogden, 1965 and C. thysi (Puylaert, 1970) from catfishes Heterobranchus bidorsalis Geoffroy Saint-Hilaire (Clariidae) in Sierra Leone and Parauchenoglanis punctatus (Boulenger) (Claroteidae) in the Democratic Republic of Congo, respectively ( Inglis and Ogden 1965, Puylaert 1970a), and C. leberrei and C. williamsi ( Puylaert, 1970a) from amphibians in Togo, Sudan and Swaziland, and from Sierra Leone, respectively (see Rizvi et al. 2016). Two other species of this genus, C. alaini Alfonso-Roque, 1981 and C. dehradunensis Rizvi, Bursey et Maity, 2016 , are known from amphibians in Indonesia and India, respectively (see Rizvi et al. 2016).

The genus Buckleynema includes four inadequately described species, all from freshwater fishes in India: B. buckleyi Ali et Singh, 1954 from Mystus cavasius (Hamilton) (Bagridae) , B. channai Gupta et Srivastava, 1983 from Channa striata (Bloch) (Channidae) , B. notopteri Gupta et Srivastava, 1983 from Notopterus notopterus (Pallas) (Notopteridae) and B. singhi Rai, 1969 from Sperata seenghala (Sykes) (Bagridae) (see Sood 1989).

By its general morphology and in having the mouth with six circumoral cuticular lobes, the present specimen should belong to Chabaudus . However, the validity of this genus is questionable. The cephalic end of the type species of Gendria , G. tilapiae , was studied in apical view by Chabaud (1956) and Inglis (1967) under the LM; they reported the oral aperture to be circular, without lips, but their line drawings are too schematic, indicating that slightly developed circumoral cuticular lobes might have been easily overlooked. Moreover, cephalic cuticular lobes (or lip-like formations) may be poorly developed in some species of Chabaudus , as for example in C. dehradunensis , and in different congeneric species the shape of mouth is from triangular to hexagonal, and might apparently appear as almost circular; the shape of the proper oral aperture may be circular, as visible in the present specimen ( Fig. 10D ). Reliable data on the cephalic structure of other species of Gendria are absent, only Vassiliadẻs and Chevalier (1973) illustrated six lip-like formations on the cephalic end (in apical view) of G. polypteri studied by LM, which is, however, characteristic of Chabaudus .

Taking into account the above discussion, in our opinion the reported differences in the shape of mouth (hexagonal or circular) cannot be taken for the feature of a generic importance and, therefore, we consider Chabaudus to be a junior synonym of Gendria . Accordingly, species listed in the former genus are transferred to Gendria as G. alaini (Alfonso-Roque, 1981) comb. n., G. chabaudi ( Inglis et Ogden, 1965) comb. n., G. dehradunensis ( Rizvi, Bursey et Maity, 2016) comb. n., G. thysi (Puylaert, 1970) comb. n. and G. williamsi (Puylaert, 1970) comb. n.

Gendria longispiculata sp. n. is easily distinguished from all other species of Gendria , as well as of those belonging to Buckleynema , by its conspicuously long spicules; whereas spicules of the new species measure 1.2 mm and, when withdrawn, they reach anteriorly the level of the ventral sucker, those in all other species of Gendria and Buckleynema are at most 570 µm long (but usually much shorter), reaching anteriorly to about mid-length between the cloacal opening and the ventral sucker or less when withdrawn. The new species also differs from its congeners from African fishes in the shape of the oesophagus or cephalic vesicle, distribution of postanal papillae and in the host family ( Schilbeidae vs Cichlidae , Clariidae , Claroteidae and Polypteridae ).

The presence of a row of small denticles at the edge of the oral apeture ( Fig. 11D,E ) in a species of Gendria is reported for the first time. Similar denticles at the edge of the oral aperture are also present in representatives of some other seuratoid genera, e.g. Cucullanus Müller, 1777 , Seuratum Hall, 1916 or Skrjabinura Gnedina, 1933 (see Inglis 1967). Gendria longispiculata is the first quimperiid species reported parasitising catfishes of the family Schilbeidae .

Figures

Fig. 10. Gendria longispiculata sp. n. from Schilbe grenfelli (Boulenger), male. A – anterior end of body, sublateral view; B – same, larger magnification; C, D – cephalic end, sublateral and apical views, respectively; E – posterior end, lateral view; F, G – tail, lateral and ventral views, respectively.

Fig. 11. Gendria longispiculata sp. n. from Schilbe grenfelli (Boulenger), scanning electron micrographs of male. A – anterior end of body, lateral view; B, C – cephalic end, apical and sublateral views, respectively; D – edge of oral aperture with row of denticles; E – same, enlarged denticles; F – deirid; G – posterior end of male, ventrolateral view; H – anterior portion of body, lateral view (arrow indicates deirid). Abbreviations: a – amphid; b – cephalic papilla of outer circle; c – cephalic papilla of inner circle; d – ventral sucker; o – oral aperture; v – cephalic vesicle.

Fig. 12. Gendria longispiculata sp. n. from Schilbe grenfelli (Boulenger), scanning electron micrographs of male. A – posterior end of body, lateral view; B – subventral genital papilla located anterior to ventral sucker; C, D – caudal end, lateral and ventral views, respectively (arrows indicate genital papillae). Abbreviations: c – cloacal opening; d – ventral sucker; m – median precloacal papilla.