Morphological characterisation of Dactylogyrus spp. (Platyhelminthes: Monopisthocotylea) from Enteromius spp. (Cypriniformes) in Cameroon, with description of a new species.

Monogeneans are fish ectoparasites which infested commonly gill filament. They are characterised by their sclerotized haptoral and genital structures. Morphological study of gill monogeneans was conducted at Lebamzip, Center Region of Cameroon. Fish were caught along Cesala River. Each monogenean was mounted between slide and coverslip in a drop of GAP mixture. Drawings of the sclerotized structures were made using Corel Draw and measurements were taken on Amscope. Four monogeneans species belonging to the genus Dactylogyrus were identified. One new species is described Dactylogyrus cesalaensis n. sp. from Enteromius aspilus and three described species as follows: Dactylogyrus aspili from Enteromius aspilus; Dactylogyrus mendehei and Dactylogyrus nyongensis from Enteromius guirali are rediscribed. Each monogenean species presented a filamentous anchor and MCO with a flame type accessory piece. Particularly, Dactylogyrus cesalaensis n. sp. has a W-shaped dorsal bar; filamentous hooks; vagina shaped like a dagger blade. For Dactylogyrus aspili: dorsal bar is V-shaped; pair I of hooks most developed without filament; pairs II-VII are filamentous; vagina is a leaf-like piece with spiny ends. Concerning D. mendehei: pair I of hooks without filament; pairs II-VII are filamentous; dorsal bar U-shaped. For D. nyongensis: dorsal bar arched; filamentous hooks; three forms of MCO belonging to the flame type observed; vagina comma-shaped. All encountered monogeneans are classed in the Dactylogyrus wunderi type. Colonisation-extinction phenomena and variability of abiotic factors inherent to the study area explained the parasitic richness and morphometric differences observed during this study, respectively.