Rhabdochonidae Travassos, Artigas et Pereira, 1928

Rindoria, Nehemiah M., Morara, George N., Smit, Willem J., Truter, Marliese, Smit, Nico J. & Luus-Powell, Wilmien J., 2023, Integrated morphological and molecular characterization of the fish parasitic nematode Rhabdochona (Rhabdochona) gendrei Campana-Rouget, 1961 infecting Labeobarbus altianalis (Boulenger, 1900) in Kenya, International Journal for Parasitology: Parasites and Wildlife 21, pp. 201-209 : 203-205

Family Rhabdochonidae Travassos, Artigas et Pereira, 1928 .

Rhabdochona (Rhabdochona) gendrei Campana-Rouget (1961) ( Fig. 2A–F , 4 A-H)

Syns: Nec Spiroptera acuminata Molin, 1859 ; Nec Spiroptera acuminata Von drasche, 1883; Nec Oxyspirura acuminata Stossich, 1897 ; Nec Rhabdochona acuminata Travassos, Artigas et Pereira,1928 ; Rhabdochona acuminata sensu Gendre (1922) and Nec Rhabdochona acuminata Vaz et Pereira, 1934 .

General description: Medium-sized nematodes. Tetragonal oral opening with a pair of adjacent amphids and four submedian cephalic papillae surrounding the opening. Prostom funnel-shaped, armed with 14 anterior teeth. Vestibule straight, relatively long. Deirids averagesized, biforked/bifurcate, situated approximately mid-length of vestibule. Tail of both sexes conical, with sharply pointed tip.

Male (9 specimens): Length of body 6.02–9.36 (7.36) mm, maximum width 110.40–169.90 (140.06). Vestibule including prostom 131.04–171.20 (153.50) long; length of prostom 21.36–24.80 (23.11), width 17.22–20.74 (18.86). Length of muscular oesophagus 272.45–430.14 (342.76), of glandular oesophagus 2.65–3.92 (3.16) mm. Deirids, nerve ring, and excretory pore 78.23–85.45 (81.53), 205.56–231.84 (216.28), 278.14–311.21 (298.29) from anterior extremity, respectively. Preanal papillae 10–12 pairs: 9–11 sub-ventral and 1 lateral pairs; latter pair approximately at level of third subventral pair (counted from cloacal aperture). Postanal papillae 6 pairs: 5 subventral and 1 lateral pairs; latter pair approximately at level of first subventral pairs (counted from cloaca aperture). Left spicule 426.79–576.30 (519.01) long. Right spicule 150.26–177.94 (161.29) long, tapering at its distal end, without usual dorsal barb. Length ratio of spicules 1:2.57–3.76 (3.23). Tail 263.71–577.69 (348.26) long, with cuticular spike at tip.

Female (5 specimens): Length of body 9.88–20.55 (14.18) mm, maximum width 138.37–348.50 (268.26). Length of vestibule including prostom 148.34–200.35 (163.77); prostom 22.92–24.32 (23.63) long, 15.94–19.11 (17.95) wide, with distinct basal teeth. Deirids, nerve ring and excretory pore 91.56–120.12 (104.20), 221.34–254.63 (236.34), and 311.56–351.02 (328.45), respectively, from anterior extremity. Vulva postequatorial, 4.32–11.36 (8.00) mm from posterior end of body. Size of mature (larvated) eggs 458.75–474.04 (476.66) length,

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302.74–353.63 (324.80) width. Tail conical, 274.54–428.43 (348.64) long, with distinct cuticular spike at end.

Host: Labeobarbus altianalis (Boulenger, 1900) ( Cyprinidae , Cypriniformes ).

Site of infection: Intestine.

Locality/collection date: River Nyando (Lake Victoria Basin) Kisumu County, Kenya (000 ′ 0 ◦ 22 ′ S, 34 ◦ 51 ′ E 35011 ′ E) (see Fig. 1 ) (collected May 3 and August 3, 2022, by Drs. Nehemiah M. Rindoria and George N. Morara) .

Prevalence and intensity of infection: 100% (32 fish parasitized of 32 fish examined); 6–11 nematodes.

Deposition of voucher specimens: A total of twelve voucher specimens (six adult female and six male) were deposited in the Helminthological Collection of the Institute of Parasitology , the Biology Centre of the Czech Academy of Sciences, Cesk ˇe´Budˇejovice, Czech Republic ( IPCAS N-1030 ) .

Deposition of sequences: Sequence data obtained were deposited in GenBank: 28S rRNA (OR096360–OR096361), cox 1 (OR088887–OR88888).

Comments. Reports of Campana-Rouget (1961), Puylaert (1973) and Vassiliad`es and Troncy (1974) did not record any measurements on this parasite, but the morphology of specimens of the present material is in agreement with their descriptions. Morphometrics of the taxonomic relevant features of R. gendrei from the present study is within the ranges recorded by Moravec (1972) who gave a redescription of the same nematode from B. duchesnii .

Figures

Fig. 2. Rhabdochona (Rhabdochona) gendrei Campana-Rouget (1961) from Labeobarbus altianalis (Boulenger, 1900), scanning electron micrographs of the male. A – cephalic end, subapical view; B – deirid; (circled); C, D – posterior end of male, ventrolateral view (white stars and white circles indicate a pair of lateral pre- and postanal papillae, respectively); E – right spicule; F – excised right spicule, following enzymatic digestion. Abbreviations: a – amphid; 1–11, and 1–9 – pairs of sub-ventral preanal papillae (in C); 1–5 – pairs of postanal papillae (in D).

Fig. 4. Rhabdochona (Rhabdochona) gendrei Campana-Rouget (1961) from Labeobarbus altianalis (Boulenger, 1900), scanning electron micrographs of a female. A (deirids shown by white circle), B, C – cephalic end dorsolateral and anterior views; D– lateral view of the excretory pore (as shown by white arrow); E – detail of vulva sub-ventral view; F, G – fully mature (larvated) eggs dissected out of the nematode body; H – tail tip (white arrows shows openings with a papilla); Abbreviations: a – amphids; c – submedian cephalic papilla; pt – anterior prostomal teeth.

Fig. 1. A map of River Nyando, in Lake Victoria Basin, showing the study locations at Koru and Ahero.