Circadian and circannual rhythms in air gulping behaviour of cave fish

Study of the biological rhythms in cavernicoles is of considerable interest especially since the cave ecosystem is characterized by absence of light, relatively constant temperature and relatively high and constant humidity. The present paper documents for the first time multifrequency biologic rhythms in air gulping behaviour of a cavernicolous fish Oreonectus evezardi, kept under complete darkness, DD. A circadian rhythm was demonstrated with statistical significance by cosinor method for air‐gulping activity during 9 months out of 14 months of observations. A 6‐monthly rhythm in circadian mesor was detected. However, statistically significant circannual rhythms in circadian amplitude and circadian acrophase were validated. Thus, results of the present study clearly demonstrate semicircannual or circannual modulation of the circadian behavioural rhythm of a cave dwelling teleost.