Influence of ionic contents on the stratification of astomatia and hysterocinetidae (ciliophora, oligohymenophora) along the digestive tract of alma emini (oligochaete, glossoscolecidae) from the center region of Cameroon

The intestinal liquid of A. emini was extracted using the vacuum aspiration technique, followed by measurement of ion concentrations and concomitantly recorded species abundance. Nitrate (NO3-) concentration decreased from the foregut to the hindgut. Nitrites (NO2-), ammoniums (NH4+) and orthophosphates (PO43-) reached their greatest levels in the midgut. Furthermore, correlation analyses between ion contents and ciliate abundance in different compartments were performed. In the foregut, a positive and significant correlation was found between the abundance of the Paracoelophrya ebebdensis and PO43-. In the midgut, a positive and significant correlation was observed between the number of the ciliates Dicoelophrya mediovacuolata; Coelophrya roquei; Coelophrya ovales; Ptychostomum commune and NO2-; Almophrya mediovacuolata and NH4+. In this same compartment, a positive and significant correlation was also observed between the abundance of Ptychostomum prolixus and NO2-. In the hindgut, a positive and significant correlation was found between the values of PO43- and Ptychostomum variabilis abundance. These results suggest that each portion of the digestive tract of A. emini can be considered as a set of natural micro-habitat in which a large number of ions generate ecological niches suitable for the Survival of a specific group of ciliate species.