Abstract
Caves are a special environment in which to study the persistence of circadian rhythms in animals living in an apparent non cyclic environment. Diversity of animals from caves has been studied in order to detect circadian activity in different behaviors. This study reports that most spiders of the families Dipluridae and Ctenidae, found in the deepest and middle zones respectively of the Los Riscos cave, in Querétaro State, México, present circadian rhythms of locomotor activity in free running, and light-dark cycles induce a notable change in circadian period, suggesting an entraining of the locomotor activity rhythm. We discuss the existence of remnant circadian photoreceptors in a nonphotic environment, but also that nonphotic zeitgebers may entrain circadian activity of the fauna inside the cave.
Acknowledgements
We thank T. Bosques-Tistler for helpful comments and the English edition. Adriana Espino del Castillo, Miguel A. Hernández Patricio, Yunuén Ávila, Marisol E. Vega Orihuela, Itzel Sigala Regalado, Stephanie Ortega García and Ricardo Paredes León (Biospeleology group, Facultad de Ciencias, UNAM) for assistance on field expeditions. Fernado Álvarez Padilla and Uriel Garcilazo Cruz for their help with spiders taxonomy. Financial assistance was provided by the program PAPIIT, UNAM, Grants IN221906, IN226010 and IN 219113 to J.B.M-M.