Species of the monogenean genus Quadriacanthus mainly infect fish belonging to the Siluriformes, especially the genera Clarias, Heterobranchus or Bagrus, and their host specificity is strict (oioxenous) or narrow (stenoxenous). An examination of the gills of 19 Papyrocranus afer from Lake Ossa, South Cameroon, revealed for the first time the presence of a species of Quadriacanthus from a fish host belonging to the Notopteridae. The morphology and the size of sclerotized parts of haptor and the male and female copulatory complexes suggest that this monogenean is a new species named Quadriacanthus euzeti n. sp. The fish genus Papyrocranus differs taxonomically from the usual fish hosts of Quadriacanthus and hence the presence of a species belonging to this genus on the gills of this host suggests the occurrence of a lateral transfer of Quadriacanthus from species belonging to Clarias or Bagrus which live sympatrically with P. afer in Lake Ossa.

MONOGENEAN PARASITES FROM CLARIIDAE (TELEOSTEI, SILURIFORMES) IN CAMEROON: I. DESCRIPTION OF TWO NEW SPECIES OF GYRODACTYLUS FROM THE NYONG BASSIN The study of gill and skin parasites of three fishes species belonging to the genus Clarias: C. camerunensis, C. jaensis and C. pachynema, from the Nyong basin (Cameroon), revealed the presence of two new Monogenean species of the genus Gyrodactylus Nordmann: G. camerunensis n. sp. and G. nyongensis n. sp. parasite of Clarias camerunensis, C. jaensis and C. pachynema. Gyrodactylus camerunensis n. sp. is clearly distinguished from G. nyongensis n. sp. by the smaller size of the haptor sclerites. These two new species differ also from their closest african relatives of the genus Gyrodactylus , G. rysavyi, G. clarii and G. alberti, by the morpholohy and size of the haptorail sclerites. Their host specificity was discussed and appeared stenoxenous (mesostenoxenous).

Clariid catfishes are characterized by the presence of a unique arborescent supra-branchial organ formed by the second and fourth gill arches, which enables them to breathe atmospheric oxygen (Teugels & AdriAens 2003). This family contains 15 genera and includes 89 species that occur in the freshwaters of Africa (13 genera, 74 species), Asia Minor (1 species, also present in Africa), and South East Asia (3 genera and 15 species) (Agnèse & Teugels 2005). In Cameroonian freshwaters, 4 genera:

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).

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.

Host specimens were sampled in the middle course of the River Sanaga (Cameroon) from January to October 2014. Two new species, Protoancylodiscoides auratum n. sp. from Chrysichthys auratus and Protoancylodiscoides combesi n. sp. from C. auratus, Chrysichthys nigrodigitatus and Chrysichthys longidorsalis, are herein described. These new helminths differ from the congeneric species by the size of the haptoral sclerites, the male copulatory organ length, the diameter and morphology of the vagina. At this stage, the present study suggests that Protoancylodiscoides auratum is oioxenous, while P. combesi is stenoxenous. The two new Protoancylodiscoides species bring to three the number of those parasitizing C. auratus, and to four the number of those described from Chrysichthys spp.

IN CAMEROON. II. DESCRIPTION OF THREE NEW SPECIES OF BIRGIELLUS N. GEN. (DACTYLOGYRIDEA, ANCYROCEPHALIDAE) IN THE NYONG BASIN A study of monogenean gill parasites from three species of the genus Clarias Scopoli, 1777 (Clariidae), namely Clarias camerunensis Lönnberg, 1895, C. jaensis Boulenger, 1909 and C. pachynema Boulenger, 1903, from the Nyong basin (Cameroon) revealed the presence of three new monogenean species of the new genus Birgiellus, namely Birgiellus mutatus n. sp. from C. pachynema, B. calaris n. sp. from C. jaensis and B. kellensis n. sp. from C. camerunensis. The genus Birgiellus differs from the genus Quadriacanthus by the morphology of the ventral bar composed of a single piece (two distinct in Quadriacanthus) and the size of the uncinuli IV, which are not much different from the others (longest in Quadriacanthus). Birgiellus calaris differs from B. mutatus by its ventral anchors longer and larger, the morphology of the ventral bar with a short incision between the two branches, and a long and trapezoid handle, the size of the sclerotised structures of the male and female copulatory organs, the larger thickness of the hook in the male accessory piece, the latter having also a heel. Birgiellus kellensis is closer to B. calaris but can be distinguished by the small size of its dorsal and ventral anchors, its transverse bars, male copulatory organ, and the accessory piece, which also has not a heel but a secondary blade. According to the clause 8.5.2 of the International Zoological Code of Nomenclature (1999) the genus Birgiellus and the species B. mutatus and B. calaris, respectively, replace Claridectes, C. clarisa and C. alacris previously described by Birgi (1987), but whose specimens were not deposited in a museum. All the three taxa described exhibit a strict (oioxenous) host specificity. Résumé : L'étude des monogènes parasites branchiaux de trois espèces de poissons du genre Clarias Scopoli, 1777 (Clariidae) : C. pachynema, C. jaensis et C. camerunensis, pêchés dans le bassin du Nyong (Cameroun) a permis de récolter trois nouvelles espèces placées dans le nouveau genre Birgiellus, respectivement Birgiellus mutatus n. sp. chez Clarias pachynema, B. calaris n. sp. chez C. jaensis et B. kellensis n. sp. chez C. camerunensis. Le genre Birgiellus, voisin du genre Quadriacanthus, s'en distingue par la morphologie de la barre transversale ventrale formée d'une pièce unique (deux bras distincts chez Quadriacanthus) et par les uncinuli IV peu différents des autres (plus grands chez les Quadriacanthus). Birgiellus calaris diffère de B. mutatus par les anchors ventraux plus longs et plus épais, la morphologie de la barre transversale ventrale, la taille des pièces sclérifiées des appareils copulateurs mâle et femelle, avec la pièce accessoire mâle munie d'un talon, un manche trapézoïdal plus long et un crochet plus épais. Birgiellus kellensis, proche de B. calaris, s'en écarte par la taille plus faible des anchors dorsaux et ventraux, des barres transversales, du pénis, et de la pièce accessoire male,...

Objectifs : Le but de cette étude a été d'investiguer sur le mode de répartition de Protoancylodiscoides combesi et P. auratum monogènes parasites branchiaux de Chrysichthys auratus (Siluriformes, Claroteidae), communément appelé machoiron, un poisson abondamment exploité dans l'ensemble du bassin de la Sanaga, afin de déterminer les mécanismes qui influencent leur fixation.