Effect of photoperiod on the attachment and development of immature Ixodes persulcatus Schulze (Acarina : Ixodidae)

Abstract

Host attachment activity and development of larvae and nymphs were observed in I. persulcatus held in the laboratory under constant temperature (25℃), with various photoperiodic conditions (10L-14D, 12L-12D and 16L-8D). Larval attachment was hardly affected by photoperiod during the stages from eggs to unfed larvae, but nymphal attachment was inhibited by exposing to a short-day photoperiod (10L-14D) during the stages from engorged larvae to unfed nymphs. Both engorged larvae and nymphs were strongly affected by the photoperiodic conditions under which they were held before, during and after engorgement. The active development of engorged larvae occurred in exposure to a long-day photoperiod (16L-8D) before and/or during and after engorgement. The diapause of engorged larvae was induced by exposing to short-day photoperiods (10L-14D or 12L-12D) throughout the stages from eggs to engorged larvae. The diapause of engorged nymphs occurred in response to short-day photoperiods during and after engorgement. Exposure of engorged nymphs to a long-day photoperiod during and after engorgement prevented diapause. These results suggest that I. persulcatus is a long day type with a facultative diapause in the larval and nymphal stages. It is considered that the diapause of I. persulcatus larvae and nymphs, which is induced by short-day photoperiods, plays an important role in the synchronization of the activities of the nymphs and adults under favorable seasonal conditions of spring to summer.