The light–dark cycle of Desmoulin’s whorl snail Vertigo moulinsiana Dupuy 1849 (Gastropoda, Pulmonata, Vertiginidae) and its activity patterns at different temperatures

Abstract

Vertigo moulinsiana is a minute land snail species which requires high humidity conditions and is found in wet, temporarily inundated habitats. The species is listed in the IUCN Red List of Threatened Species under the VU (vulnerable) category and is considered a high conservation priority. It is also mentioned in Annex II of the EU Habitat Directive, which imposes the obligation to monitor the species in member countries. The monitoring of V. moulinsiana is based on counting individuals attached to plants in the field, and thus any results may only be properly evaluated when the behavior of the species is understood. Therefore, the aim of this study was to investigate the light–dark cycle of both adults and juveniles within the species as well as to compare activity patterns of both age groups in dark conditions in temperatures of 6 ºC and 21 ºC. Observations were carried out under laboratory conditions, at a high and constant humidity (humidity was at or nearly 100 %). It was shown that juveniles were more active than adults during the day, at night, and at 6 ºC and 21 ºC. In addition, both age groups of V. moulinsiana were more active at 21 ºC than at 6 ºC, and their activity was higher at night than during the day. Such behavior may have an impact on monitoring results based on visual examination and should be taken into account when the data are interpreted