Love story or fling? The first observation of Vorticella sp. (Ciliophora: Peritrichia) on the freshwater snail Gyraulus rossmaessleri (Auerswald, 1852)

Shells of Gyraulus rossmaessleri (Auerswald, 1852) infested with the bell-shaped peritrich ciliate Vorticella sp. were found in small, flooded soil depressions located in a floodplain meadow in the Upper Rhine Valley (north-eastern France). The observed prevalence was 100%. Analysis of the distribution of Vorticella aggregates on planispiral shells shows that the epibionts occur largely in the pseudo-cavities formed by the apex and umbilicus and mainly along the suture. This is the first case of ciliated epibionts on gastropods associated with temporary freshwater habitats inhabited by drought-adapted fauna. However, given the scarcity of observations of G. rossmaessleri in this region, it is difficult to affirm whether this epibiosis is relatively common.