Cucullanus congolensis, Moravec & Jirků, 2017

Moravec, František & Jirků, Miloslav, 2017, Some nematodes from freshwater fishes in central Africa, Folia Parasitologica (033) 64, pp. 1-39 : 23-26

Cucullanus congolensis sp. n.

Figs. 22 , 23

ZooBank number for species:

urn:lsid:zoobank.org:act:95D554AD-8D31-47B2-9B10-FBF4BB698FA6

Description. Medium-sized nematodes. Body whitish, elongate, with slightly transversely striated cuticle. Lateral alae absent. Cephalic end somewhat asymmetrical in lateral view. Oral aperture dorsoventrally elongate, surrounded by raised narrow membranous ala (collarette) supported by row of ca 70 minute basal teeth ( Figs. 22C , 23A–C ). Four submedian cephalic papillae and pair of lateral amphids present ( Figs. 22C , 23A–C ). Oesophagus muscular, expanded at anterior end to form bulbous pseudobuccal capsule (oesophastome); posterior part of oesophagus also expanded, somewhat narrower than oesophastome in lateral view ( Fig. 22A,B ). Oesophagus opens into intestine through large valve. Nerve ring encircles oesophagus at distance representing 35–42% of oesophageal length. Deirids small, situated approximately at midway between nerve ring and posterior end of oesophagus ( Figs. 22A,B,E , 23H ). Postdeirids not found. Excretory pore in region of oesophago-intestinal junction ( Fig. 22B ). Tail of both sexes conical, sharply pointed at tip.

Male (2 specimens; holotype; measurements of paratype in parentheses). Length of body 6.7 mm (5.0 mm), maximum width 231 (163); width at level of oesophastome 165 (150), at middle of oesophagus 159 (136). Length of entire oesophagus 775 (775), representing 12% (16%) of whole body length; length of oesophastome 240 (225), its width 150 (111); minimum width of oesophagus 63 (45); maximum width of posterior part of oesophagus 120 (105). Distance of nerve ring from anterior extremity 313 (326), representing 40% (42%) of oesophageal length. Deirids and excretory pore 517 (707) and 748 (775), respectively, from anterior end of body. Posterior end of body curved ventrally. Ventral sucker and ventral precloacal oblique muscle bands absent ( Figs. 22G , 23E ). Cloacal region not elevated. Large median papilla-like formation present anterior to cloacal opening ( Figs. 22F–H , 23D–G ). Spicules equal, 480 (489) long, with rounded posterior ends ( Fig. 22G ), representing 7% (10%) of body length. Gubernaculum well sclerotised, small, rod-like with narrow proximal part in lateral view, 105 (63) long ( Fig. 22F,G ). Caudal papillae 11 pairs: 6 pairs of preanal papillae (5 subventral and 1 lateral) and 5 pairs of postanal papillae (3 subventral, 1 lateral and 1 dorsolateral); preanal pair of laterals located well anterior to cloacal opening; first postanal pair of subventrals just posterior to cloacal opening, second and third postanal pairs of subventrals in posterior half of tail; postanal pair of laterals (probably representing phasmids) slightly anterior to level of second subventral pair; papillae of dorsolateral postanal pair slightly anterior to level of last subventrals ( Figs. 22F–H , 23D–G ). Length of tail 216 (156).

Female (2 specimens with immature eggs; allotype; measurements of paratype in parentheses). Length of body 6.2 mm (8.4 mm), maximum width 204 (218); width at level of oesophastome 163 (136), at middle of oesophagus 122 (136). Length of entire oesophagus 816 (898), representing 13% (11%) of whole body length; length of oesophastome 245 (192), its width 136 (105); minimum width of oesophagus 109 (45); maximum width of posterior part of oesophagus 120 (99). Distance of nerve ring from anterior extremity 326 (313), representing 40% (35%) of oesophageal length. Deirids and excretory pore 694 (544) and 775 (870), respectively, from anterior end of body. Vulva postequatorial, 3.7 mm (4.6 mm) from anterior extremity, at 60% (55%) of body length; vulval lips not elevated. Vagina directed anteriorly from vulva. Uteri opposed, containing few immature eggs. Length of tail 231 (340); phasmids indistinct ( Fig. 22D ).

Type host: Bubu Auchenoglanis occidentalis (Valenciennes) ( Siluriformes : Claroteidae ).

Site of infection: Intestine (distal part).

Type locality: Lower Congo River , left bank near Pioka , 04°54'25''N; 14°23'53''E, and right bank near Bulu , 05°01'30''N; 14°00'25''E, Democratic Republic of the Congo (collected 7 and 11 July 2008) .

Prevalence and intensity: 2 fish infected/7 fish examined; 1 and 4 nematodes.

Deposition of type specimens: IPCAS N-1134 (holotype mounted on SEM stub, allotype and 2 paratypes in vials) .

Etymology: The species name congolensis relates to the Congo River, where this parasite was found.

Remarks. The following six nominal species of Cucullanu s have been, mostly inadequately, described from freshwater and brackish-water fishes in Africa: C. barbi Baylis, 1923 , C. baylisi Campana-Rouget, 1961 , C. clarotis Baylis, 1923 , C. djilorensis Ndew, Diouf, Bâ et Morand, 2014 , C. egyptae Abdel-Ghaffar, Bashtar, Abdel-Gaber, Morsy, Mehlhorn, Al Quraishy et Mohammed, 2014 and C. mormyri Moravec et Scholz, 2017 (see Baylis 1923a, Campana-Rouget 1961, Abdel-Ghaffar et al. 2014, Ndew et al. 2014, Moravec and Scholz 2017).

By the absence of a ventral precloacal sucker, the new species can be easily distinguished from C. egyptae , C. barbi and C. djilorensis , parasites of anguilliform, cypriniform and mugilliform fishes, respectively, in which the sucker is present. Cucullanus mormyri , a parasite of osteoglossiform fishes, differs from C. congolensis sp. n. mainly in the location of the excretory pore situated at a long distance posterior to the end of the oesophagus (vs in the region of the oesophago-intestinal junction) and the absence of lateral preanal papillae. Both C. baylisi and C. clarotis are parasites of siluriforms (catfishes) as the new species. However, C. baylisi , a specific parasite of Mochokidae ( Synodontis spp. ), possesses no lateral preanal papillae (see Moravec and Scholz 2017), in contrast to C. congolensis , in which large lateral preanal papillae are present ( Figs. 22F–H , 23D–G ).

The presence of large lateral preanal papillae, as in C. congolensis , was described and illustrated for C. clarotis (see Baylis 1923a); moreover, both species are parasites of Claroteidae . Baylis (1923a) reported female specimens of C. clarotis also from Synodontis schall (Mochokidae) , but these were subsequently assigned to C. baylisi based on a re-examination of Baylis’ original specimens by Campana-Rouget (1961). However, in contrast to the original description of C. clarotis , specimens of the present material possess a large median precloacal papilla-like formation (vs such structure not reported for C. clarotis ) and they also differ in the smaller body length of males (5.0– 6.7 mm vs 7.0–10.0 mm), shorter spicules (480–489 µm vs 800 µm) and the oesophagus (775 µm vs 850–1,100 µm), location of the excretory pore in region of the oesophago-intestinal junction (vs approximately at mid-length of oesophagus), the genus and species of fish hosts ( Aucheniglanis occidentalis vs Clarotes laticeps [Rüppel]) and different biogeographic affinity (Congolean ichthyological province vs Nilo-Sudanian ichthyological province). Although it cannot be excluded that future studies of C. clarotis may show its conspecificity with C. congolensis , for the time being we consider it more reasonable to deal with these forms as two separate species.

Figures

Fig. 22. Cucullanus congolensis sp. n. from Auchenoglanis occidentalis (Valenciennes). A – anterior end of female, dorsoventral view; B – anterior end of male, lateral view; C – cephalic end of male, apical view; D – tail of female, lateral view; E – deirid; F – tail of male, lateral view; G – posterior end of male, lateral view; H – tail of male, ventral view.

Fig. 23. Cucullanus congolensis sp. n. from Auchenoglanis occidentalis (Valenciennes), scanning electron micrographs of male. A–C – cephalic end, lateral, apical and dorsal views, respectively; D – region of cloaca, ventral view; E – posterior end lateral view; F, G – tail, lateral and ventral views, respectively; H – deirid. Abbreviations: a – amphid; b – cephalic papilla; c – cloacal opening; d – median precloacal papilla-like formation.