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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.

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.

Three new species of Synodontella Dossou & Euzet, 1993 are described from two species of Synodontis (Mochokidae) collected from the middle course of the Boumba River (East Cameroon): Synodontella angustupenis n. sp. from Synodontis nummifer , Synodontella longipenis n. sp. and Synodontella simplex n. sp. from Synodontis decorus . These new species are different from the other Synodontella species already described due to their horseshoe-shaped dorsal transverse bars. Synodontella angustupenis differs from S. longipenis and S. simplex by the morphology of its penis, a thin tube, and its accessory piece, bifid at its extremity. Synodontella longipenis differs from the other two species by the morphology and the size of its male copulatory organ, which is very long. Synodontella simplex differs from S. angustupenis and S. longipenis by the shape of its penis, which is simple, and of its accessory piece, with a developed heel. The difference between the dorsal transverse bars of Synodontella species from the Sanaga River in Cameroon (and other localities in Africa), slightly curved, and those from the Boumba River, horseshoe-shaped, makes it possible to separate Synodontella species into two different subgroups. This difference can be explained by a long isolation period of the hosts, living in different river basins, followed by the divergence of the parasite populations (vicariant speciation). Trois nouvelles espèces de Synodontella Dossou & Euzet, 1993 sont décrites chez deux espèces de Synodontis (Mochokidae) collectées dans le cours moyen de la rivière Boumba (Est Cameroun) : Synodontella angustupenis n. sp. de Synodontis nummifer , Synodontella longipenis n. sp. et Synodontella simplex n. sp. de Synodontis decorus . Ces nouvelles espèces sont différentes des autres espèces de Synodontella déjà décrites par leurs barres transversales dorsales en forme de fer à cheval. Synodontella angustupenis diffère de S. longipenis et de S. simplex par la morphologie de son pénis, un tube fin et de sa pièce accessoire, bifide à son extrémité. Synodontella longipenis diffère des deux autres espèces par la morphologie et la taille de son organe copulateur mâle, qui est très long. Synodontella simplex se distingue de S. angustupenis et S. longipenis par la forme de son pénis, qui est simple, et de sa pièce accessoire, avec un talon développé. La différence entre les barres transversales dorsales des espèces de Synodontella du fleuve Sanaga au Cameroun (et d’autres localités africaines), légèrement incurvées, et celles de la rivière Boumba, en forme de fer à cheval, permet de séparer les espèces de Synodontella en deux sous-groupes différents. Cette différence peut être expliquée par une longue période d’isolement des hôtes, vivant dans différents bassins hydrographiques, suivie de la divergence des populations de parasites (spéciation vicariante).

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.

Clarias camerunensis is a potential catfish for farming in Cameroon. In order to assess the parasitism of its monogeneans as a function of season and standard lengh, a study was conducted from April 2017 to April 2018 in Lép Mööga stream, of the Nyong river watershed (Southern Cameroon). 179 specimens of C. camerunsis were sampled by angling through 5 consecutive seasons. The Prevalence, density, abundance of adults and larvae of the main Monogenean species as well as the condition coefficient K and gonadosomatic index of the female C. camerunensis were calculated. The prevalence of the adult Quadriacanthus sp. remained equal to or greater than 85% during this study. Its abundance was low and did not show any clear profile pattern; however, its variation peaked during the rainy season. The gonadosomatic index (GSI) and condition factor (K) of female C. camerunensis evolved in parallel and showed that this fish lays three times a year, during the short rainy, the short dry and the long rainy seasons. The profile of Quadriacanthus sp. larvae showed that this monogenean breeds all year with two peaks during the short rainy season (when the female hosts lay and are weak fry also are in the environment), and in January when hosts are more concentrated in low water. The physiological condition of the fish gradually improved as they grew, when the parasitic density decreased. To limit monogenean outbreaks in farming, this work recommands that fish caught in the wild should be placed in quarantine and dewormed before being exploited.