Y-axis orientation in the South American freshwater snail species Chilina patagonica (Gastropoda: Chilinidae)

Abstract

Y-axis orientation, a movement perpendicular to the shore or coastline, enables aquatic animals to stay in a preferred zone in generally unstable habitats. Such behaviour is a widespread phenomenon in many freshwater and intertidal animal taxa. In the present study, an arena approach was used to test the orientation response of pulmonate freshwater snails. Using this experimental design, Y-axis orientation was shown for the first time in a freshwater snail species, the riverine Chilina patagonica. Some cues, potentially mediating Y-axis orientation, appeared to play no role in the shown orientation behaviour, such as chemical, gravity and humidity cues or a sun compass. Magnetic cues, however, could not be excluded. Since no significant differences in orientation were detected between different size classes in C. patagonica, orientation behaviour may not vary substantially throughout the snail's life history. In contrast to C. patagonica, no consistent orientation response was seen in the related lacustrine species Chilina llanquihuensis. The adaptation of C. patagonica to exhibit orientation along the Y-axis may be driven by the avoidance of high velocities in deeper water.

Keywords:

• behavioural ecology
• Chile
• Chilina llanquihuensis
• shoreward orientation

Acknowledgements

This is the 60th publication of the Huinay Scientific Field Station. Sincere thanks go to: Winston Ponder and two anonymous reviewers for highly valuable comments on an earlier version of this manuscript; Sebastian López Rodríguez for assistance in the field; Alfred Burian, Anita Eschner, Torsten Hauffe, Katharina Heiler, Michael S. Painter, Iris Starnberger and Thomas Wilke for comments on earlier versions of the manuscript; Reinhard Fitzek for friendly advice at the Huinay Scientific Field Station; the members of the ‘Schreibwerkstatt’ at the University of Vienna in the winter semester 2010/2011 and the two guiding lecturers Michael Stachowitsch and Günter Gollmann for a critical revision of a former manuscript. This study was partly funded by the Deutsche Forschungsgemeinschaft (WI 1902/4-1 and RI 809/19-1).