43.10 Thursday, Jan. 5 Y-axis orientation in South American freshwater snails (Chilina spp.) LANDLER, Lukas*; VON OHEIMB, Parm V; Virginia Tech, USA, Blacksburg and Natural History Museum of Vienna, Austria; Department of Animal Ecology and Systematics, Germany, Gießen email@example.com
Y-axis orientation, defined here as movement perpendicular to the shore- or coastline, enables aquatic animals to control migration. In the present study a new arena assay is established to test the orientation response of pulmonate freshwater snails after displacement outside the water. Using this novel experimental design, for the first time, Y-axis orientation was shown in a freshwater snail species, the riverine Chilina patagonica. In contrast to C. patagonica, no consistent orientation response could be detected in the related lacustrine species Chilina llanquihuensis. Several potential cues could be identified as probably being irrelevant for the Y-axis orientation behavior found in this study: chemical, visual, gravity, humidity cues or a sun compass. Magnetic cues, however, may play a role. Since no differences in orientation were detected in different size classes in C. patagonica, orientation behavior may not vary substantially throughout its life history. However, the preferred direction of C. patagonica seems to be contradictorily, because one would expect an orientation response towards the waterside, when placed outside the water, not away from it. In the case of C. patagonica, an adaptation to the physical constraints of its habitat might be of vital importance. We suppose that the different hydrological constraints in river habitats might influence migration and orientation in C. patagonica. The highest current velocity exists in the deepest area of the river. Orientation towards the shore is probably more viable than orientation towards the middle of the river as it prevents the gastropods from getting drifted away. Given our findings for C. patagonica, further studies might provide new insights into the underlying cues of Y-axis orientation behavior.