Cithariniella khalili Petter, Vassiliadẻs et Troncy, 1972

Moravec, František & Jirků, Miloslav, 2017, Some nematodes from freshwater fishes in central Africa, Folia Parasitologica (033) 64, pp. 1-39 : 8-11

Cithariniella khalili Petter, Vassiliadẻs et Troncy, 1972

Figs. 6 , 7

Syn.: Cithariniella gonzalezi Van Waerebeke, Chabaud,

Bain et Georges, 1988

Description (based on specimens from S. acanthomias ). Small, whitish nematodes with very long, slender tail and fine transverse striation of cuticle in cervical and middle part of body. Lateral alae not observed. Oral aperture roughly triangular, surrounded by 3 lip-like structures provided with 6 oral lamellae (2 dorsolateral and 4 ventrolateral) protruding out of mouth, 4 oval cephalic papillae and pair of lateral amphids ( Figs. 6C , 7A,B ). Buccal cavity shallow, with 3 sclerotised longitudinal flaps, each of them with longitudinal tooth-like structures ( Figs. 6B,C , 7B,D ). Oesophagus cylindrical, almost uniform in diameter, ending in globular bulb provided with valvular apparatus and separated from corpus by constriction (isthmus) ( Fig. 6A ). Intestine straight, narrow. Excretory pore situated relatively far posterior to level of bulb ( Fig. 6A ).

Male (10 specimens). Length of body 1.9–2.0 mm, maximum width 177–204. Buccal cavity 15–21 long. Entire oesophagus 372–522 long; length of corpus 243–399, width 30–51, length of isthmus 18–42, width 39–51, length of bulb 90–105, width 90–105. Nerve ring and excretory pore 163–174 and 517–598, respectively, from anterior extremity. Single spicule narrow, 90–108 long, with pointed distal tip; its capitulum 18–24 long ( Figs. 6D,F , 7C,E,F ). Gubernaculum weakly sclerotised, 33–42 long. Region of cloacal opening elevated, bearing 1 pair of large subventral preanal papillae and 2 pairs of small postanal papillae located on 2 large subventral postcloacal lobes ( Figs. 6F,G , 7C,E,F ). Two parallel or nearly parallel papillae located close to each other situated 66–108 posterior to cloacal aperture (at 19–36% of length of tail) and 159–282 from end of tail ( Figs. 6F,H , 7E,F ). Pair of minute lateral phasmids located approximately in mid-way between last two pairs of caudal papillae ( Fig. 7E ). Ventral precloacal pseudosucker absent. Tail conical, attenuated, 272–354 long, representing 14–18% of body length ( Fig. 6F ).

Female (10 gravid specimens). Length of body 3.0– 3.5 mm, maximum width 245–367. Buccal cavity 27–33 long. Entire oesophagus 501–552 long; length of corpus 342–399, width 63–69, length of isthmus 30–39, width 51– 60, length of bulb 105–120, width 105–132. Nerve ring and excretory pore 195–204 and 340–394, respectively, from anterior extremity. Vulva situated 1.86–2.24 from anterior extremity (at 60–66% of body length), 435–598 anterior to anus; vulval lips not elevated ( Figs. 6E , 7G ). Vagina muscular, directed anteriorly from vulva. Uterus filled with many eggs. Eggs elongate, thin-walled, unembryonated, provided at each pole with many very long thread-like filaments; eggs 114–132 long, 39–45 wide ( Fig. 6I ). Tail 598–680 long, representing 18–23% of body length ( Fig. 6E ).

Host: Synodontis acanthomias and S. greshoffi Schilthuis (both Siluriformes : Mochokidae ).

Site of infection: Intestine.

Localities: Lower Congo River, right bank near Bulu, Democratic Republic of the Congo, 05°01'30''N; 14°00'25''E ( S. acanthomias , collected 11 July 2008); and Sangha River adjacent to Sangha Lodge, 02°59'06''N; 16°13'59''E ( Congo basin), DSPA, Central African Republic ( S. greshoffi , collected 11–12 September 2012).

Prevalence and intensity: S. acanthomias : 2 fish infected/4 fish examined; 11–41 nematodes. S. greshoffi : 2/9; 12–16.

Deposition of voucher specimens: IPCAS N-906.

Remarks. To date, Cithariniella Khalil, 1964 contains five valid species, all parasitic in African freshwater fishes: C. citharini Khalil, 1964 (type species), C. khalili , C. koubkovae Moravec et Van As, 2015 , C. longicaudata Moravec et Van As, 2015 and C. petterae Khalil, 1974 (see Moravec and Van As 2015a). The identification of present specimens as C. khalili is based on their general morphology, especially the shape and size of cephalic papillae and presence of two closely adjoing ventral postanal papillae located some distance posterior to cloaca on the male tail ( Petter et al. 1972, Koubková et al. 2010, Moravec and Van As 2015a).

The cephalic end of C. khalili (misidentified as C. citharini ) was previously first studied using SEM by Moravec (1994) based on specimens from Synodontis schall in Egypt and later by Mašová (2012) in the same host species from Lake Turkana, Kenya, who also studied the eggs using this method. Mašová (2012) referred to Synodontis frontosus , but molecular determination confirmed identity of host as S. schall ; data will be published elswhere. Koubková et al. (2010) used SEM for observing specimens of C. khalili from four species of Synodontis Cuvier in Senegal and reported the presence of lateral alae in both males and females (but this feature is not visible on their micrographs). However, no lateral alae were found in specimens examined in the present study. Nevertheless, our SEM examinations confirmed the most important taxonomic features of C. khalili (see above), and, for the first time, showed the presence of two small postanal papillae on each of the two large subventral postcloacal lobes (the lobes were previously considered to be large single papillae) and minute phasmids.

According to Moravec and Van As (2015a), C. khalili is a parasite of African catfishes of the genus Synodontis (Mochokidae) , reported from Synodontis batensoda Rüpel , S. frontosus , S. longirostris Boulenger , S. membranaceus (Geoffroy Saint-Hilaire) , S. nigrita Valenciennes , S. ocellifer Boulenger , S. schall (type host), S. serratus and S. sorex Günther (all Mochokidae ) and, exceptionally, from catfishes of other families, e.g. Auchenoglanis biscutatus (Geoffroy Saint-Hilaire) (Claroteidae) , in Chad, Central African Republic, Senegal, Egypt, Sudan and Kenya (e.g. Petter et al. 1972, Moravec 1974a, Vassiliadẻs and Troncy 1974, Fahmy et al. 1976, El-Naffar et al. 1983, Van Waerebeke et al. 1988, Imam et al. 1991, Koubková et al. 2010; Mašová 2012, Moravec and Scholz 2017). The present finding of this parasite in S. acanthomias and S. greshoffi from the Democratic Republic of the Congo and Central African Republic, respectively, represents new host and geographical records.

Figures

Fig. 6. Cithariniella khalili Petter, Vassiliadẻs et Troncy, 1972 from Synodontis acanthomias Boulenger. A – anterior end of young female, lateral view; B, C – cephalic end, lateral and apical views, respectively; D – spicule and gubernaculum, lateral view; E – posterior end of young female, lateral view; F – posterior end of male, lateral view; G – distribution of caudal papillae in region of cloaca, ventral view; H – last pair of postcloacal papillae, ventral view; I – egg (only basal parts of filaments illustrated).

Fig. 7. Cithariniella khalili Petter, Vassiliadẻs et Troncy, 1972 from Synodontis acanthomias Boulenger, scanning electron micro- graphs. A – cephalic end of male, apical view; B – cephalic end of female, apical view; C – region of cloaca, ventral view; D – cephalic end of female, dorsolateral view; E, F – region of cloaca and anterior part of tail, subventral and ventral views, respectively (arrow indicates phasmid); G – posterior part of female body, ventral view. Abbreviations: a – amphid; b – cephalic papilla; c – cephalic lamella; e – preanal papilla; f – postanal double papilla; g – median pair of postanal papillae situated some distance posterior to cloaca; h – vulva; i – anus.