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In the Upper Congo Basin, there are few records of monopisthocotylan parasites from clariids. More surveys of clariid fishes can lead to the discovery of multiple monopisthocotylan species that are new to the region or new to science. We aimed to investigate the monopisthocotylan parasite fauna belonging to Quadriacanthus of five clariid fishes in the Upper Congo Basin by (i) inventorying the species composition and providing the description of new species when necessary, and (ii) analysing their infection parameters. Clarias ngamensis, C. stappersii, C. buthupogon, C. gariepinus and C. theodorae were purchased from fishermen in the Lufira, Lubumbashi and Kafubu rivers in the Upper Congo Basin. Monopisthocotylans were mounted on glass slides with ammonium picrate-glycerin for identification based on morphological analysis of genital and haptoral sclerotised parts. Eight species, namely Q. aegypticus, Q. allobychowskiella, Q. amakaliae, Q. domatanai, Q. halajiani, Q. kalomboi n. sp., Q. bassocki n. sp. and Q. shigoleyae n. sp. are reported. The most prevalent parasite species was Q. amakaliae on C. stappersii (prevalence 60%) with a mean infection intensity of 9.8 ± 7.7. We report C. stappersii and C. buthupogon as new hosts for species of Quadriacanthus as well as three new parasite species for science and new localities for the first five parasite species mentioned above. The new records and the description of Q. kalomboi n. sp., Q. bassocki n. sp. and Q. shigoleyae n. sp. increase the knowledge of the diversity of monopisthocotylans in this region.

Recently in Cameroon, two species belonging to Quadriacanthus : Q. anaspidoglanii Akoumba, Tombi & Bilong Bilong, 2017 and Q. euzeti Nack, Pariselle & Bilong Bilong, 2016 have been recorded on gill filaments of Notoglanidium macrostoma (Siluriformes, Claroteidae) in the Memou’ou River (Nyong Basin) and Papyrocranus afer (Osteoglossiformes, Notopteridae) in Lake Ossa, respectively. These records have been considered the result of lateral transfers from Clariidae to a Claroteidae host for the first case (parasitism of N . macrostoma by Q . anaspidoglanii ) and from Clariidae or Bagridae to a Notopteridae host for the second (parasitism of P . afer by Q . euzeti ). In this paper, the investigation of interspecific relationships among Quadriacanthus spp. parasitizing Clariidae, Bagridae, Claroteidae and Notopteridae in Cameroon resulted in the record of Q. anaspidoglanii from N . macrostoma , Q . euzeti from P. afer , a new record of Q . levequei Birgi, 1988 from Clarias jaensis in the Nyong River, and the description of Q . barombiensis n. sp. from Clarias maclareni in Lake Barombi Mbo. The newly identified species is characterized by having an accessory piece ending in one small hook and the median expansion of its dorsal bar with two filaments. Phylogenetic analysis based on 28S rDNA sequences confirms that the Quadriacanthus spp. parasitizing gill filaments of non-clariid hosts in Cameroon originate from lateral transfers from clariid fishes, and that Clariidae are ancestral hosts of these monogenean species. Récemment au Cameroun deux espèces appartenant à Quadriacanthus  : Q. anaspidoglanii Akoumba, Tombi & Bilong Bilong, 2017 et Q. euzeti Nack, Pariselle & Bilong Bilong, 2016 ont été signalées, respectivement sur les filaments branchiaux de Notoglanidium macrostoma (Siluriformes, Claroteidae), dans la rivière Memou’ou (bassin du Nyong) et Papyrocranus afer (Osteoglossiformes, Notopteridae) dans le lac Ossa. Ces signalements ont été considérés comme le résultat de transferts latéraux de Clariidae vers un hôte Claroteidae pour le premier cas (parasitisme de N. macrostoma par Q. anaspidoglanii ) et d’un Clariidae ou Bagridae vers un hôte Notopteridae pour le second (parasitisme de P. afer par Q. euzeti ). Dans cet article, l’étude des relations interspécifiques entre Quadriacanthus spp. parasitant des Clariidae, Bagridae, Claroteidae et Notopteridae au Cameroun a abouti au signalement de Q. anaspidoglanii chez N. macrostoma , Q. euzeti chez P. afer , un nouveau signalement de Q. levequei Birgi, 1988 chez Clarias jaensis dans le fleuve Nyong, et à la description de Q. barombiensis n. sp. chez Clarias maclareni dans le lac Barombi Mbo. L’espèce nouvellement identifiée se caractérise par la présence d’une pièce accessoire se terminant par un petit crochet et l’expansion médiane de sa barre dorsale avec deux filaments. L’analyse phylogénétique basée sur les séquences d’ADNr 28S confirme que les Quadriacanthus spp. des filaments branchiaux parasitant des hôtes non-clariidés au Cameroun proviennent de transferts latéraux de poissons clariidés, et que les Clariidae sont bien les hôtes ancestraux de ces espèces de monogènes.

Clariidae is a group that includes many species that have great economic importance in both fisheries and fish culture. Monogenean parasites of fishes assigned to this family have been studied in Cameroon, but there have been no studies on Clarias submarginatus Peter, 1882, a fish that is traditionally consumed by the local people. The examination of 43 specimens identified as C. submarginatus from Lake Ossa (first record of this fish species in the Sanaga basin), revealed that some of them belong to Quadriacanthus and are new. Their identification was made based on the morphology and the size of sclerotized parts of the haptor and the male and female copulatory complexes. Quadriacanthus macruncus Bahanak, Nack [amp]amp; Pariselle sp. nov. and Quadriacanthus submarginati Bahanak, Nack [amp]amp; Pariselle sp. nov. are characterized by the morphology of their accessory piece, pointed, slightly curved and wider at medium level, equipped with two subterminal, symmetrical and similar spines for Q. macruncus sp. nov. and made up of one long tip flanked by a short spine and a bulb for Q . submarginati sp. nov., while Quadriacanthus ossaensis Bahanak, Nack [amp]amp; Pariselle sp. nov. is distinguished by the unique morphology of the penis, ending in a fork. The new species of Quadriacanthus are herein described and their host specificity is discussed.

ABSTRACT Monogeneans are among the main parasites affecting aquaculture worldwide. The present study describes four new species belonging to Schilbetrema, which is only known from African catfishes. Host specimens were sampled from the Sanaga Basin and from the Boumba River (Congo Basin) using gill nets or purchased at local fish markets. Four new species, namely Schilbetrema bilongi sp. nov., Schilbetrema sanagaensis sp. nov., Schilbetrema ducentesimum sp. nov. from Schilbe mystus (Linnaeus, 1758) and Schilbetrema asambaensis sp. nov. from Schilbe intermedius Rüppel, 1832 are described. Schilbetrema bilongi sp. nov. is close to S. spirocirra in the morphology of the dorsal anchors; it differs in the morphology of the dorsal bar, distal part of the accessory piece, dorsal anchor length and number of turns of the male copulatory organ (MCO). Schilbetrema ducentesimum sp. nov. is close to S. hexacornis in the morphology of the ventral anchors, ventral bar and MCO; it differs in the morphology of the dorsal bar, length of the dorsal anchor, MCO and presence of to two light sclerotised parts. Schilbetrema sanagaensis sp. nov. is close to S. ducentesimum sp. nov. in the morphology of the dorsal bar and ventral anchors; it differs from this species by the morphology of the dorsal anchors, the distal extremity of the accessory piece, MCO length and the length of the dorsal anchors. Schilbetrema asambaensis sp. nov. resembles S. eutropii and S. calamocleithrum. It differs from S. calamocleithrum by the morphology of the accessory piece, the ventral bar, MCO length; and from S. eutropii by the morphology of the ventral bar and MCO length.

ABSTRACT Monogenean parasites belonging to Quadriacanthus have never been reported from Clarias ngamensis, but are commonly found on congeners. In view of the specificity of monogeneans, the genetic proximity and the co-occurrence of C. ngamensis and C. gariepinus in Africa, it is hypothesised that a parasitological survey of C. ngamensis will yield several species of Quadriacanthus as its congeneric host C. gariepinus harbours these parasites. The present study aims to explore the monogenean parasites from the gills of C. ngamensis in the Upper Congo Basin by (i) inventorying their diversity and providing their morphological characterisation, and (ii) analysing their infection parameters. Monogeneans were isolated from the gills, and identified based on morphological analysis of genital and haptoral sclerotized parts. Seven parasite species belonging to Quadriacanthus were found. Among them, two species, Q. aegypticus and Q. allobychowskiella, are both newly reported in the Upper Congo Basin and newly recorded on C. ngamensis. Quadriacanthus amakaliae sp. nov., Q. halajiani sp. nov., Q. domatanai sp. nov., Q. lubandaensis sp. nov., and Q. curvicirrus sp. nov. are new to science and described herein. The most prevalent parasite species was Q. curvicirrus sp. nov. in the Luapula River (prevalence = 66.7%) with mean infection intensity of 6.3 ± 5.8. Quadriacanthus allobychowskiella and Q. aegypticus are known parasites from C. gariepinus and their presence on C. ngamensis is probably the result of lateral transfers. The discovery of five new species from C. ngamensis highlights the parasite diversity still to be explored in the region.

ABSTRACT Chrysichthys nigrodigitatus (Lacépède) specimens were sampled in the Sanaga River and in the Dibamba River. Three new species, Protoancylodiscoides edeaensis sp. nov., P. yombai sp. nov. from both rivers, and P. dibambaensis sp. nov. from the Dibamba River alone, are described. Protoancylodiscoides edeaensis sp. nov., close to P. mansourensis El-Naggar, 1987 and P. chrysichthes Paperna, 1969 by the morphology of the haptor sclerotised parts, differs from these species by the penis length and the morphology of the vagina. Protoancylodiscoides yombai sp. nov. is close to P. edeaensis sp. nov., P. mansourensis, and P. chrysichthes by the morphology of some sclerotised parts of the haptor (ventral bar, ventral anchors, dorsal onchium and hooks). However, it differs from these species by the morphology of the vagina, of the outer root of the dorsal anchor, and the size of some sclerotised parts (dorsal anchor total length, dorsal bar length, ventral anchor length, and penis length). Protoancylodiscoides dibambaensis sp. nov. is close to P. ivoiriensis Bouah, N’Douba & Pariselle, 2021 by the lack of the onchium and the morphology of some sclerotised parts of the haptor. However, it differs from this species by the morphology of the dorsal bar, penis length, dorsal bar length, and of the ventral anchor total length. This study on monogeneans raises the question of ichthyofauna exchange between adjacent streams; it also reveals a longitudinal gradient of Protoancylodiscoides species richness in the Sanaga River.

Monogenean flatworms are mainly parasitic in lower aquatic vertebrates including fish, anurans and chelonians. Quadriacanthus is one of the four genera infecting African clariids. To date, 45 members of the genus are described, but this is still embryonic compared to the expected parasite and host species richness in Africa. In this study, we examined the gills of five species of Clarias: Clarias ngamensis, C. stappersii, C. buthupogon, C. gariepinus and C. theodorae. Eight parasite species morphologically characterised as belonging to Quadriacanthus were identified, among them five known species and three that are newly described here. In view of the importance of the clariids in this study system, this part of aquatic biodiversity is still to be further studied to contribute to inventorying parasite species in Africa.