Abstract
The aim of the present study was to determine the factors that are involved in termination of a non-diapause type of ovarian arrest in the adult macropterous females of a flightless bug, Pyrrhocoris apterus (L.), reared under a long-day (18L : 6D) photoperiod. Application of an active analogue of juvenile hormone, methoprene, to adult macropterous females kept under the above conditions induced precocious termination of ovarian arrest and shortened the length of the pre-oviposition period. The results indicate that a temporary ovarian arrest in spontaneously fasting long-day macropterous females results from a deficiency of juvenile hormone. The length of the pre-oviposition period was shortened and ovarian arrest terminated also by de-alation, high temperature and by a prolonged period of starvation. Mating of long-day macropterous females with reproductively active males had no effect on the length of the pre-oviposition period. There was a relationship between the length of the starvation period and the post-feeding pre-oviposition period. The longer the starvation period, the shorter the period from when food was supplied to first oviposition. The results indicate that depletion of the fat body reserves resulting from prolonged fasting, followed by resumption of food intake are pre-requisites for full activation of the corpus allatum and egg development, and play a role in completion and termination of non-diapause ovarian arrest in long-day macropterous females. This phenomenon was never observed in short-day brachypterous females in reproductive diapause.
Highlights
The firebug, Pyrrhocoris apterus (L.), is a common Palaearctic species from the family Pyrrhocoridae characterized by a non-functional wing-polymorphism (Socha, 1993; HonČk, 1995)
The aims of the present study were to determine (1) what factors are involved in the termination of the nondiapause ovarian arrest in long-day macropterous females of P. apterus, (2) if inhibited reproduction and prolonged pre-oviposition period results from a decrease in juvenile hormone (JH) in the body below the threshold stimulating the growth of vitellogenic ovaries, and (3) whether it is a depletion of energy reserves in the fat body that serves as a stimulus for renewed food intake and termination of the ovarian arrest in long-day macropterous females of this bug
The results indicate that a high dose of JH accelerated the termination of a non-diapause ovarian arrest in long-day macropterous females of P. apterus
Summary
The firebug, Pyrrhocoris apterus (L.), is a common Palaearctic species from the family Pyrrhocoridae characterized by a non-functional wing-polymorphism (Socha, 1993; HonČk, 1995). The long-winged (macropterous) and short-winged (brachypterous) specimens of this bug are flightless (Socha & Zemek, 2000a) Both wing polymorphism and reproductive diapause in this bug are controlled by photoperiod and temperature (Hodek, 1968; HonČk, 1976; Socha, 2001). Histolysis of flight muscles coincides with increased food intake and egg development (Socha & Šula, 2006). These data indicate that the trade-off between dispersal and reproduction, involving flight muscle development vs ovarian growth (“oogenesis-flight” syndrome), which occurs in many flying insects, is present in wing-polymorphic species that disperse only by walking and is termed the “oogenesis-walking” syndrome (Socha, 2004)
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