Dactylogyrus yassensis Musilová, Řehulková & Gelnar, 2009

Fankoua, Sévérin-Oscar, Bayiha, Etienne Didier Bassock, Nyom, Arnold Roger Bitja, Rahmouni, Imane, Nlôga, Alexandre Michel Njan & Bilong, Charles Félix Bilong, 2022, Three new Dactylogyrus species (Monogenea: Dactylogyridae) and redescription of one other, gill parasites of five Labeo spp. (Cypriniformes: Cyprinidae) from the Sanaga basin (Cameroon, Central Africa), Zoologia (e 21009) 39, pp. 1-12 : 7-8

Dactylogyrus yassensis Musilová, Řehulková & Gelnar, 2009

Fig. 6

Type host and locality. Labeo coubie , Gambia River near the Campement du Lion, Niokolo-Koba National Park , Senegal .

Other records. Labeo senegalensis , Niger River (Bamako), Baoulé River (Missira), Mali; Guiers Lake, Senegal, ( Guégan et al. 1988); Labeo coubie , Gambia River near the hotel Simenti, Niokolo-Koba National Park, Senegal; Labeo horie Heckel, 1847 , While Nile, Kosti, Sudan; Blue Nile, Sennar.

Present record. Labeo batesii, 1911 in Sanaga at Nachtigal (04°20’50.1”N; 011°38’00.3”E) , in Sanaga at Ndokoa (04°23’56.64”N; 011°44’14.52”E) , National Park of Mpem and Djim (5° 6’37.23”N; 11°33’28.91”E) and Assamba (04°24’33”N; 011°49’47.34”E) .

Infection site. Gill lamellae.

Prevalence. 60%

Mean intensity. 5.2

Material studied. Whole mounted specimens in GAP.

Redescription. Body length 594.3 (491.9–758.7; n = 7); width 141 (100.7–206.4; n = 7) at the level of ovary. Cephalic glands present, two pairs of eyes present anterior to the pharynx. Single pair of anchors (dorsal); long inner root truncate; short outer root blunt; curved shaft slightly swollen at level of filament hitch; point not reaching level of tip of inner root. Dorsal bar bonelike, with short truncate posteromedial process; ventral bar reduced, vestigial. Presence of 7 pairs of hooks, similar with larval form, approximately same length except hooks pairs I and V. One pair of needles located near hooks of pair V. No sclerotized vagina observed. Copulatory organ is a coiled wide tube, winds around the accessory piece. Accessory piece slightly sclerotized, articulated to base.

New measurements of haptoral and reproductive sclerites are given in Table 1 .

Remarks. The morphology and measurements of the specimens parasitizing Labeo batesii in the Sanaga basin ( Cameroon) correspond to the original description of Dactylogyrus yassensis from L. coubie in five countries: Niger, Mali, Ghana, Gambia and Senegal ( Musilová et al. 2009; Pravdová et al. 2018). The only difference that could be detected is that of the penis length 82.3–95 µm vs 74–79 µm from the original description by Musilová et al. (2009) in West Africa. Dactylogyrus yassensis can be confused with D. omega but differs mainly from it by larger anchor, dorsal bar smaller and without fenestrated extremities, penis length longer, and the other sclerotized structures slightly smaller.

Morphometric study by PCA

The principal component analysis (PCA) performed on the measurements of sclerotized parts of the haptor and the MCO showed that Monogeneans collected in the present work belong to four well distinct groups ( Fig. 7 ). With regard to the haptor data and the MCO, axe 2 isolated two subsets made up of two groups each. Axe 1 separated D. nachtigalensis sp.nov. from “ D. sanagaensis sp.nov. + D. longiphaloides ” on the one side, and D. yassensis from “ D. djimensis sp.nov. + D. omega ” on the other side.

Figures

Figure 6. Drawing of sclerotized parts of Dactylogyrus yassensis. (DA) dorsal anchor, (DB) Dorsal bar, (VB) ventral bar, (Pe) penis, (AP) accessory piece, (Vg) vagina, (N) needle. Scale bar: 20 Μm.

Figure 7. Result of the principal component analysis performed on measurements (Μm) of sclerotized parts of monogeneans.