Feeding conditions modify the photoperiodically induced dispersal of the water strider, Aquarius paludum (Heteroptera: Gerridae)

Tetsuo Harada,Tatsuya Nishimoto

doi:10.14411/eje.2007.005

Abstract

Overwintering adults of the water strider, Aquarius paludum were collected from the field in fall and kept under short days (12L : 12D) at 20Â°C for a week. A control group was then kept at 12L : 12D and fed daily, and three experimental groups were transferred to 15.5L : 8.5D and fed at different frequencies: daily or every 2nd or 3rd day. Temperature was kept at 20Â°C. Flight behaviour of the adults in the four groups was recorded every 10 days up to the end of the 5th week when the adults were dissected. State of the flight muscles and reproductive organs (ovaries and testes) was recorded. Flight ability of the adults fed every 3rd day (Group 3) was higher than that of those fed daily (Group 1). Seventy percent of the females that were fed every 3rd day (Group 3) remained in diapause for 5 weeks, in spite of the reproduction promoting long-days, while none of the females fed every day remained in diapause (Group 1). Flight muscle histolysis, promoted by long-days, was inhibited by poor feeding conditions. Thus, they can migrate and seek more suitable water bodies rich in food. The modifying effect of the availability of food on the trade-off between reproduction and flight is recorded here for the first time for a carnivorous insect.

Highlights

Control of diapause induction or diapause development may be achieved by integrating photoperiod and food conditions in some insects, including carnivorous insects
They were exposed to a low temperature of 7°C for 2 days to promote the development of flight muscles (Harada et al, 2003) and kept under conditions of 12 h light – 12 h dark (12L : 12D) and 20 ± 2°C for a week, which are similar to those prevailing in the field in late fall at Kochi
Strong support for an adaptive trade-off between flight ability and reproduction is provided by comparative studies of wing-polymorphic insects belonging to several orders (Denno et al, 1989; Roff & Fairbairn, 1991; Zera & Denno, 1997)

Summary

Introduction

Control of diapause induction or diapause development may be achieved by integrating photoperiod and food conditions in some insects, including carnivorous insects. Several water striders which inhabit fresh water, use photoperiod to regulate their reproductive and dispersal characteristics, including wing length and flight muscle maturation (Spence & Andersen, 1994; Harada et al, 2000, 2005). Aquarius paludum, for example, photoperiod is the main environmental factor regulating several life history traits such as reproduction, wing length, flight muscle condition, flight ability, and resistances to high and low temperatures and drying-out (Harada, 2003a, b). Whereas short days induce reproductive diapause or the maturation of flight muscles and flight in A. paludum (Inoue & Harada 1997; Harada et al, 2000). Increasing photoperiod, even when shorter than the critical photoperiod for diapause induction, can inhibit flight and promote the histolysis of flight muscles (Inoue & Harada, 1997). This paper reports the results of a laboratory experiment designed to test this idea

Methods

Results

Conclusion