Induction Of Reproductive Diapause Research Articles

Life history of the flea beetle, Argopistes coccinelliformis Csiki(Coleoptera: Chrysomelidae). VII. Effects of photoperiod and temperature on induction of reproductive diapause in newly emerged adults.

Life history of the flea beetle, Argopistes coccinelliformis Csiki(Coleoptera: Chrysomelidae). VII. Effects of photoperiod and temperature on induction of reproductive diapause in newly emerged adults.

The role of neurosecretory neurons in the pars intercerebralis and pars lateralis in reproductive diapause of the blowfly, Protophormia terraenovae.

Microlesions of the brain were made to examine the role of neurosecretory neurons in the pars intercerebralis (PI) and pars lateralis (PL) in the induction of reproductive diapause of the female blowfly Protophormia terraenovae. Under both diapause-inducing (LD 12:12, 20 degrees C) and diapause-averting conditions (LD 18:6, 25 degrees C), the ovaries invariably failed to develop when the PI was removed. When the PL was removed bilaterally, the ovaries developed in most of the females, irrespective of the rearing conditions. Removal of the PL prevented females from entering reproductive diapause. These results show that certain neurosecretory neurons in the PI are necessary for vitellogenesis, and that the PL contains inhibitory neurons which suppress vitellogenesis during reproductive diapause.

Photoperiod and Reproductive Diapause in the Predatory Bugs Anthocoris tomentosus, a. antevolens, and Deraeocoris brevis (Heteroptera: Anthocoridae, Miridae) with Information on Overwintering Sex Ratios

The effect of photoperiod on induction of reproductive diapause was determined for 3 species of predatory bugs inhabiting the pear and apple growing regions of the Pacific Northwest. Females of Anthocoris tomentosus Péricart, A. antevolens White (Anthocoridae), and Deraeocoris brevis (Uhler) (Miridae) were more likely to enter reproductive diapause (characterized by undeveloped ovaries and well-developed fat body) under short-day conditions than under long-day conditions. Critical photoperiods were between 16:8 and 15:9 (L:D) h in D. brevis, and between 15:9 and 14:10 [L:D] h in A. tomentosus. Results for A. antevolens were less clear because females in this species often failed to reproduce even under long-day conditions (18:6 and 16:8 (L:D) h). A small number of A. tomentosus and A. antevolens that failed to mature ovaries also failed to accumulate large fat reserves. Duration of the preoviposition period in nondiapausing insects was shortest in A. tomentosus (9 d), of intermediate duration in D. brevis (10–11 d), and longest in A. antevolens (12–13 d). Overwintering sex ratios were highly biased in the 2 anthocorids (79–95% female), and were moderately biased in D. brevis (60% female). Overwintering samples of 2 other anthocorid species, Orius tristicolor (White) and A. whitei Reuter, also were female-biased (100% female for both species). Dissections of females indicated that insects having undeveloped ovaries and well-developed fat body could be collected from the field most of the summer. Numbers of teneral adults in the dissections showed peaks in late July (A. tomentosus and A. antevolens) and in early August (D. brevis).

Induction of reproductive diapause via perception of photoperiod through the compound eyes in the adult blow fly, Protophormia terraenovae

Covering and surgical removal of the compound eyes were performed to localize photoreceptors for photoperiodic responses in the blow fly Protophormia terraenovae (Diptera, Calliphoridae). Adult females showed a long-day photoperiodic response to control reproductive diapause. When the compound eyes were bilaterally covered with silver paint, diapause incidence increased under diapause-preventing conditions, i.e., a long-day photoperiod and constant light, as though flies were kept under constant darkness. Neither silver painting on a medial region of the head capsule nor control painting in which both compound eyes were painted in a clear solvent caused significant effects on diapause incidence. Unilateral painting of the compound eye caused an increment of diapause incidence under constant light but no effects under a long-day photoperiod. When the compound eyes were bilaterally removed, all the flies developed their ovaries both under a long-day and a short-day photoperiod. Unilateral removal of the compound eye also caused ovarian development under a short-day photoperiod, whereas removal of one antennal lobe or all ocelli caused no effects on diapause incidence. Since P. terraenovae completely lost responsiveness to photoperiod after blinding of the compound eyes, it is likely that this fly perceives photoperiod through its compound eyes.

Photoperiodic Induction of Reproductive Diapause in the Predators Nabis americoferus and Nabis roseipennis (Heteroptera: Nabidae)

The predators Nabis americoferus (Carayon) and N. roseipennis Reuter are common in several agroecosystems and overwinter as adults. Studying females, we found that the critical photoperiod for induction of reproductive diapause at 24°C is between 13.5 and 14.0 h light per day for both species. To determine the stage most sensitive to diapause inducing photoperiods, pairs of cohorts were reared to various points in their development under a photoperiod of 15 h light per day (not diapause inducing) or a photoperiod of 11 h light per day (diapause inducing) and then reciprocally switched to the opposite photoperiod for the remainder of development. Fewer than 10% of the individuals entered diapause when switched from the not diapause inducing to the diapause inducing photoperiod at the beginning of the adult stage. In contrast, when individuals were moved from the not diapause inducing to the diapause inducing photoperiod at the beginning of the 5th stadium, 78.4% of the N. americoferus and 87.5% of the N. roseipennis entered reproductive diapause as adults. When either species was switched from the not diapause inducing to the diapause inducing photoperiod at the beginning of any earlier stadium, 100% of the cohort entered reproductive diapause as adults. Thus, the nymphal stage is the most sensitive to diapause inducing photoperiods. Reciprocal switches from the diapause inducing to the not diapause inducing photoperiod showed that the adult stage must continue to experience a short photophase for diapause to occur. Once the critical photoperiod is reached during late summer in the field, of course, individuals will experience diapause inducing photoperiods for the remainder of their development.

Induction of Reproductive Diapause in Empoasca fabae (Homoptera: Cicadellidae) and its Implications Regarding Southward Migration

To determine if the phenology of Empoasca fabae (Harris) includes reproductive diapause, the progeny of females collected in Louisiana were reared under various conditions of photoperiod and temperature. Adults were paired, and the oviposition of each female was recorded for 40 d at 4-d intervals. Short day lengths resulted in a lower proportion of E. fabae ovipositing, a longer preoviposition period, and a decreased rate of oviposition. These responses constitute evidence for the induction of reproductive diapause. To determine whether reproductive diapause is expressed in northern populations in the field, 4th and 5th instars from New York state were reared at intervals through summer and fall. and tested for response to photoperiod. The proportion of E. fabae females becoming reproductively mature decreased as the season progressed. Less than 50% of field-reared females became gravid after mid-July. In the laboratory, reproductive maturation in field-reared females was retarded by short day lengths, but not by long day lengths. The induction of reproductive diapause in late summer supports the hypothesis that E. fabae engages in a diapause-mediated southward migration to its overwintering area.

Induction and termination of diapause in Orius predatory bugs

AbstractPhotoperiodic induction of reproductive diapause at 18 °C was investigated in four Orius [Heteroptera: Anthocoridae] species. Orius insidiosus (Say) displayed a long‐day response with a critical photoperiod between L11:D13 and L12:D12. Diapause in this species was terminated rapidly when the temperature and/or the daylength were increased. Orius majusculus (Reuter) also displayed a long‐day response. The critical photoperiod fell between L14:D10 and L16:D8. Diapause in this species was not terminated within 14 days when both temperature and daylength were increased. In Orius albidipennis (Reuter) no diapause could be induced at photoperiods varying from L8:D16 to L16:D8. In Orius tristicolor (White) a high proportion of diapause was found at all photoperiods tested.The effect of temperature on photoperiodic induction of diapause was studied in O. insidiosus at L10:D14. Diapause occurred at 18 °C, 21 °C and 25 °C, but not at 30 °C. Again, diapause was terminated rapidly after transfer to 25 °C/L16:D8. Exposing only the nymphal instars 1–5 to short daylength was not enough to induce diapause in the whole population of O. majusculus. Orius predatory bugs are used as biocontrol agents against western flower thrips, Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidael, in greenhouses. The consequences of photoperiodic induction of diapause for the success of early season releases of Orius are discussed.

The photoperiodic clock of Drosophila triauraria: Involvement of a circadian oscillatory system

The involvement of the circadian oscillatory system in the photoperiodic induction of reproductive diapause of Drosophila triauraria was examined by the resonance, Bünsow and bistability experiments. When reared with a Nanda-Hamner (resonance) protocol from the egg stage to the 16-day adult stage, this species showed a circadian oscillation in diapause incidence, but the oscillation was gradually damped when the scotophase was extended. When transferred from continuous light to the Nanda-Hamner protocol on the day of eclosion, the insect showed less distinct oscillation. Temperature affected the rate of diapause incidence, but did not affect the pattern of oscillation. On the other hand, the Bünsow and bistability experiments failed to reveal the involvement of the circadian oscillatory system in this photoperiodic clock. These results suggest that the circadian oscillatory system constitutes a part of the photoperiodic clock of this species but plays a limited role in its photoperiodic time measurement. We propose a novel model for the photoperiodic time measurement system of this species.

Effect of larval density on development and induction of reproductive diapause in Bruchidius atrolineatus

AbstractIn Bruchidius atrolineatus (Pic), an increase in larval density inside the seed led to a reduction in the survival rate during post‐embryonic development, with only a limited decrease in the weight of adults. A high larval density increased the proportion of adults in reproductive diapause under certain thermoperiodic conditions. Under other conditions that already promote the emergence of a high proportion of diapausing beetles, an increase in larval density had no effect on diapause.There was no correlation between the larval developmental time and the weights of adults in a strain with a very low incidence of diapause. However, such a correlation was observed when both sexually‐active and diapausing beetles emerged. This correlation was explained by the longer developmental times and lower weights of diapausing beetles.RésuméInfluence de la densité larvaire sur le développement et l'induction de la diapause reproductrice chez Bruchidius atrolineatus Pic(Coléoptère, Bruchidae)Chez Bruchidius atrolineatus, l'accroissement de la densité larvaire à l'intérieur de la graine entraîne une augmentation de la mortalité alors que la réduction de poids des individus à l'émergence est relativement limitée. L'accroissement de la densité larvaire provoque une augmentation du taux d'adultes en diapause reproductrice, dans certaines conditions thermopériodiques. Dans d'autres conditions, permettant l'émergence d'un fort taux d'adultes diapausants, l'effet de la densité larvaire est nul. Lorsque l'on analyse l'effet de la densité chez les individus d'une souche ne présentant pas de phénomène de diapause, il n'y a pas de corrélation entre la durée de développement et le poids des adultes. Par contre, lorsqu'il y a émergence d'adultes sexuellement actifs et diapausants, il existe une corrélation entre la durée de développement et le poids des adultes émergeants. Cette corrélation est due au fait que les adultes diapausants, qui présentent les durées de développement les plus longues, sont ceux qui ont les poids les plus faibles.

Induction of reproductive diapause in Bruchidius atrolineatus during the dry season in a Sahelian zone

AbstractBruchidius atrolineatus (Pic) (Bruchidae: Coleoptera) is a bruchid beetle infesting Vigna unguiculata (Walp). During the dry season, adults are in reproductive diapause. Studies of adult populations in a traditional store containing contaminated pods of V. unguiculata show that the reproductive diapause is induced during the first larval instars. The temperature decrease from November to January probably is the main climatic factor inducing this diapause. The percentage of diapausing adults depends on the duration of the larval development at low temperatures. Experiments in climatic boxes confirm these results. At 12 h 25 °T–12 h 20° C 11–13 LD, a high proportion of the adults emerging from the V. unguiculata seeds are in reproductive diapause and the duration of their growth is variable. L1 L2 L3 larvae probably are sensitive stages to the thermal variations and the processes allowing emergence of diapausing adults probably are induced during these larval instars.RésuméInduction de la diapause reproductrice chez Bruchidius atrolineatus coléoptère bruchidae durant la saison sèche en zone SahélienneBruchidius atrolineatus (Pic) est un Coléoptère Bruchidae se développant en zone sahélienne aux dépens d'une légumineuse Vigna unguiculata. Pendant la saison sèche, les adultes sont en diapause reproductrice. Un suivi des populations d'adultes a été réalisé dans un grenier traditionnel en ‘terre séchée’ contenant des gousses récoltées dans la nature et portant des œufs de B. atrolineatus. Il a permis de constater que la diapause reproductrice était induite durant les premières phases du développement larvaire. La décroissance des températures de Novembre à Janvier avec des minima de 15 °C et des maxima de 25 °C est probablement le principal facteur permettant l'induction de cette diapause. L'introduction dans le grenier de gousses portant des œufs venant d'être émis à différentes périodes de la saison sèche montre que le pourcentage d'adultes diapausants dépend de la durée du développement larvaire aux températures ‘basses’. Des expériences réalisées dans des étuves programmées confirment ces résultats. A 12 h 25 °T/12 h 20 °C 11–13 LD, un taux élevé d'adultes émergeant des graines est en diapause reproductrice et la durée de leur développement post‐embryonnaire est très variable. En conditions plus chaudes 12 h 40 °C/12 h 25 °C 11–13 LD, le taux d'adultes diapausants est plus réduit et la durée du développement plus courte. L'analyse de la croissance larvaire montre que les premiers stades larvaires sont probablement des stades sensibles aux variations thermiques. Les modifications physiologiques permettant l'émergence d'adultes diapausants ou sexuellement actifs seraient induites durant ces stades.

Change in Photoperiodic Sensitivity during Hibernation in a Semi-Aquatic Bug, Microvelia douglasi (Heteroptera : Veliidae)

Timing of induction of reproductive diapause of Microvelia douglasi were investigated. Diapausing females began to appear in early September in field population. Under laboratory condition at 24°C, reproductive diapause was induced by photoperiods shorter than 12.5 hr of light, which concides with the daylength in early September. Seasonal changes in the pattern of egg production of overwintering females incubated under laboratory conditions at 24°C were also examined. When the insects were incubated under 16L-8D photoperiod, almost all the females began to lay eggs irrespective of the sampling date. When incubated under 12L-12D and 8L-16D, the percentage of females which laid eggs was low in samples collected before December, but it became as high as 100 percent in samples collected after December. The preoviposition period from the date of the collection increased until the end of October, decreased to 5 to 6 days in lae December and stayed at a constant level thereafter. Although females incubated under 16L-8D continued to lay eggs throughout experimental period, some females, which were incubated under 12L-12D and 8L-16D, stopped laying eggs soon after beginning of incubation. However, under 12L-12D, the percentage of such females decreased in samples collected later in the winter.

Effects of diet composition on cold adaptation in temperate collembola

1. 1. The effects of diet composition on initiation and termination of cold hardiness in the temperate collembolan species Orchesella einem (L.) was studied in relation to reproductive activity. 2. 2. Induction of cold hardiness was not related to the induction of reproductive diapause. 3. 3. The degree of achieved cold hardiness was proportional to the nitrogen availability in the food, while reproductive activity ceased independently of the food source. 4. 4. At the termination of cold hardiness a negative relation between reproductive activity and cold hardiness was found. 5. 5. Growth of juveniles was proportional to the nitrogen availability in the food. At the induction of cold hardiness, juveniles had an overall lower growth rate than at the termination of cold hardiness.

Photoperiod, dormancy and the end of flight activity inChrysopa corneaStephens (Neuroptera: Chrysopidae)

AbstractThe flight activity ofChrysopa carneaSteph. was studied during 1970–77 using 21 suction traps sited between 50 and 58°N. in northwestern Europe. Flight continues until late October and early November, well beyond the time (late August) when reproductive diapause is initiated at these latitudes. Flight ends as an all-or-none response to changing daylengths, the most northern populations having a shorter critical photoperiod, about 10 h 20 min, between morning and evening civil twilights, than the most southern ones, the critical photoperiod of which is about 10 h 45 min. By contrast, the critical photoperiod for induction of reproductive diapause is longer in northern populations. At latitudes less than 30° N. there is no winter dormancy but there is sometimes aestivation during the hottest period of the summer. InC. carnea, uniquely, winter dormancy has two distinct components, reproductive diapause and loss of flight activity, each controlled independently by photoperiod.