Non-diapausing Pupae Research Articles

Effect of Photoperiodic Transfer and Brain Surgery on the Photoperiodic Control of Pupal Diapause and Seasonal Morphs in the Swallowtail, Papilio xuthus L.(Lepidoptera : Papilionidae)

Larvae of Papilio xuthus were transferred from short-day to long-day conditions at various developmental stages. The critical time, at which the short-day (diapause inducing) effect was cancelled by the following long-day (diapause averting) conditions in 50 per cent of the larvae, was at around the 4th larval ecdysis at 20°C. In the reversed transfer, the critical time was 3 days earlier.In general, there is a close association between the induction of diapause and the spring morph, while the summer morph emerges from non-diapause pupae. This tendency was obscured in the autumnal field population as well as in non-diapause pupae subjected to photoperiodic transfer in the larval stage or to a low temperature during the pupal stage.Association of the seasonal morphs with the developmental pattern was also disturbed by removal of one of the brain lobes, where the mechanisms underlying the photoperiodic control of diapause and seasonal morphs are presumably located.

In Vitro Studies on the Role of the Brain and Prothoracic Glands in the Pupal Diapause of Manduca Sexta

ABSTRACT Pupal diapause in the tobacco hornworm, Manduca sexta (Johannson), is characterized by the absence of an increased ecdysteroid titre in the haemolymph during the first week of pupal life as measured by radioimmunoassay. This virtual absence of the steroid moulting hormone is thought to be responsible for the diapause state and it is apparently a consequence of the failure of the diapausing pupal prothoracic glands (PG) to synthesize ecdysone at an increased rate. In Manduca, this apparent failure of PG activation during diapause may be in response to two endocrinological circumstances: the curtailment of PTTH release as opposed to its synthesis and transport, and the development of refractoriness of the gland to stimulation by PTTH. The former was examined by measuring PTTH activity present in brains and brain-retrocerebral complexes of diapausing and non-diapausing pupae and the latter by assessing PG biosynthetic activity in vitro in the presence and absence of PTTH.

SURVIVAL OF PUPAE OF HELIOTHIS VIRESCENS AND HELIOTHIS ZEA (LEPIDOPTERA: NOCTUIDAE) AT LOW TEMPERATURES

AbstractMortality of diapausing and non-diapausing pupae of Heliothis virescens (Fabricius) and H. zea (Boddie) at low temperatures was assessed in the laboratory. Comparison of the exposure time necessary to induce 50% mortality (LT50) indicated that survival of diapausing pupae was significantly higher than that of non-diapausing pupae. Similar comparisons showed no consistent significant differences in mortality of pupae from different geographic locations within Texas or in pupae preconditioned in several different ways. One exception was the response of pupae of H. virescens preconditioned to varying temperatures. This type of preconditioning appeared to increase the cold-hardiness of pupae at subfreezing temperatures. Contact moisture significantly decreased LT50 values of pupae of both species at sub-zero temperatures. Predictive models for low temperature mortality were developed for dry, diapausing pupae.

Glycerol accumulation in developmentally arrested pupae of Papilio machaon obtained by brain removal

Brains were removed from non-diapausing pupae of Papilio machaon within 24 hr after pupation. The developmentally arrested pupae were examined for glycerol metabolism by comparison with naturally diapausing pupae. The decerebrate non-diapausing pupae accumulated appreciable amounts of glycerol (13.0 mg/ml haemolymph) during exposure to 5°C for 2 months. However, this amount was considerably lower than that accumulated in the naturally diapausing pupae (24.5 mg/ml) under the same conditions. A difference was also observed in the initial level of the glycogen in the fat body. The naturally diapausing pupae contained about 105 mg/g glycogen, while the decerebrate non-diapausing pupae contained only about 70 mg/g, one day after pupation.

Diapause and development in the tobacco budworm, Heliothis virescens: A comparison of haemolymph ecdysteroid titres

The signal to induce diapause in H. virescens comes early in development (prior to the third instar in most insects), but the signal to break diapause can come shortly after entrance into diapause at pupation. Haemolymph ecdysteroid titres in both diapause-bound and non-diapause-bound Heliothis virescens larvae were similar in the first two thirds of the last-larval instar, when similar changes in morphology and behaviour occurred. However, the number of stepwise increases in titre and the timing of the steps was different in the two groups of larvae. Haemolymph ecdysteroid titres in the last third of the instar were approx, five times higher in non-diapause than in diapause-bound larvae. In diapausing pupae, haemolymph ecdysteroid titres dropped to levels found in larvae which had completed two thirds of the last instar. When diapausing pupae were warmed to break diapause, haemolymph ecdysteroid titres rose again. However, 2 of the 4 high ecdysteroid levels detected in pupae developing after diapause break were considerably lower than those detected for non-diapause pupae.

Ecdysteroids and diapause in pupae of Heliothis punctiger

Most pupae of H. punctiger enter diapause when reared at 19°C, 12L:12D. When pharate pupae were treated for only 12 hr at 28°C about 50% developed at 19°C. The proportion of non-diapausing pupae increased as the temperature at which the pharate pupal stage was spent increased. The quantity of injected 20-hydroxyecdysone necessary to promote development in diapausing pupae varied from about 1 μg g −1 soon after pupation to about 4 μg g −1 after 50 days. It fell somewhat after 150 days. Removing brains from non-diapausing pupae showed that the brain secreted its hormone at the time of pupation (or just before). However, if the pupae were kept at 19°C development did not occur unless the brain remained in situ for at least 20 hr at 28°C. Implanting brains from non-diapausing pupae into diapausing ones had no measurable effect. These results may be explained by postulating that the prothoracic gland is ‘activated’ by exposure to high temperature, but that it reverts to inactivity over a period at 19°C. The ‘active’ gland must then be stimulated by brain hormone for a long period to trigger secretion of its hormone, which results in development. Diapause is thus the result of the failure of the prothoracic gland to secrete.

The biosynthesis, function and fate of taurine during the metamorphosis of the noctuid moth Mamestra configurata Wlk.

Taurine is only a minor constituent of growing larvae and prepupae of Mamestra configurata. Following pupation there is a massive synthesis and accumulation of taurine in the pupa. Radioisotope experiments with [ 35S]-cysteine demonstrated that labelled cysteamine, hypotaurine and taurine were formed rapidly following the injection of labelled cysteine into two-day-old pupae. No radioactivity was found in either cysteine sulphinic acid or cysteic acid. The biosynthesis of taurine from cysteine in the pupa appears to be via: cysteine → cysteamine → hypotaurine → taurine. Newly-synthesized taurine was liberated into pupal blood and initially accumulated there. Most of the taurine in the blood of the non-diapausing pupae was taken up by developing adult structures, and especially by the flight muscles. More than 90% of the taurine synthesized during metamorphosis was found in the thorax of the adult moth, indicating an important role for taurine in the flight muscles. Diapause-programmed individuals also synthesized and accumulated large amounts of taurine following pupation. Taurine was stored in the blood of the diapausing pupa for later use when development resumed. Diapause-related functions for taurine may include membrane stabilization and diapause maintenance.

Temperature-dependent interconversion between glycogen and trehalose in diapausing pupae of Philosamia cynthia ricini and pryeri

A temperature-dependent interconversion between fat body glycogen and haemolymph trehalose was demonstrated in diapausing pupae of the silkworm, Philosamia cynthia pryeri. When pupae at early-diapause stage were placed at 2°C for several weeks, the haemolymph trehalose content increased to about 35–50 mg/ml haemolymph, whereas the trehalose content of insects maintained at 20°C remained at 5–10 mg/ml. Concomitant with this change in haemolymph trehalose level, the glycogen content of the fat body dropped from 29–41 mg to 6.6–8.6 mg/g wet weight. This interconversion could be demonstrated repeatedly if the diapausing pupae were successively exposed to high and low temperatures, although the total amount of carbohydrates decreased slightly during repeated interconversions. Non-diapausing pupae of the silkworm, Philosamia cynthia ricini, did not accumulate trehalose appreciably even when exposed to 2°C for a long period.

Pupal diapause in Heliothis armigera (Hübner) (Lepidoptera: Noctuidae) in Botswana: its regulation by environmental factors

AbstractHeliothis armigera (Hb.) has been shown to develop continuously in tropical areas but to become more dependent with increasing latitude on a pupal diapause to survive the winter. The changes that occur in pupal period under ambient conditions in Botswana were examined. Pupae formed in May were able to survive the winter period and produce adults in September. Laboratory work using artificial environments showed that this extended pupal period is not simply a response to low pupal temperatures but is induced by the low temperatures and short daylengths experienced by the larva. Pupae from larvae reared at 27° C and a 14-h daylength (non-diapause pupae) initiated adult development even at 13° C. Pupae from larvae reared at 18° C and a 9-h daylength (diapause pupae) had similar pupal periods to non-diapause pupae at 33 and 27° C. However, at 18 and 13° C, diapause pupae had much longer developmental periods than non-diapause pupae. More diapause pupae were produced at 18° C from larvae reared in a 12-h daylength than from those in 15- or 9-h daylengths. The variation and importance of this temperature-labile facultative diapause over the extensive geographical range of H. armigera is discussed.

Overwintering and spring emergence of Heliothis armigera (Hübner) (Lepi–doptera: Noctuidae) in the Namoi Valley, New South Wales

AbstractThe overwintering of Heliothis armigera (Hb.) was studied in the Namoi Valley, north-western New South Wales, Australia. In field observations, over 80% of pupae formed during late April and May were found to be in diapause and did not resume development until September. Moth emergence from diapausing pupae occurred in a protracted period between September and November. Laboratory studies indicated the probability of two phases of diapause development, one completed under cool soil conditions of winter and a second requiring a temperature above about 17° C. The threshold of the second phase was higher than that for non-diapausing pupae and was not normally reached until late September. The times to diapause termination in populations of overwintering pupae were satisfactorily fitted to a geometric distribution, which was reflected in the protracted emergence period of moths in field cages. The limited availability of suitable host-plants for the overwintering generation and for emerging moths is discussed.

PUPAL DIAPAUSE IN TROPICAL FLESH FLIES: ENVIRONMENTAL AND ENDOCRINE REGULATION, METABOLIC RATE AND GENETIC SELECTION

1. Pupal diapause in flesh flies collected within 10° of the equator may be induced by low temperature but not by photoperiod. The threshold for diapause appears to be near the fringe of ecologically relevant temperatures in each geographic area. 2. Cool temperature during the photophase elicits both a higher incidence of diapause and longer diapause than cool temperature coinciding with the scotophase. 3. Diapause persists for several months at a constant cool temperature, but four days at 25° C is sufficient to break diapause in P. spilogaster. The four-day exposure can be allocated either as a single block of time or as four one-day units spread over one month, suggesting that the fly pupa has an accurate mechanism for temperature summation. 4. Water content of the larval food exerts a minor effect on pupal diapause incidence: 10% addition of water elevated the response by 10%, and 10% decrease of water reduced the response by 18%. 5. Males and females enter diapause in approximately equal proportion. 6. When non-diapausing flies were selected for propagation, the level of diapause in P. spilogaster at 15° C dropped from 80 to 10% in ten generations. 7. Metabolic rate during diapause (7.9-10.9 µl O2/g/hr) is less than 15% of the lowest rate measured in non-diapause pupae. Infradian cycles of O2 consumption similar to, but more variable than, the pattern in temperate zone flies are observed during diapause. 8. Adult development can be initiated readily with an injection of ecdysterone. A juvenile hormone analogue is ineffective by itself but greatly enhances the ecdysterone response. Development also can be triggered with topical application of several organic solvents. 9. Diapause in the tropical flies is proposed as the evolutionary basis for the long over-wintering diapause in flesh flies that have radiated into temperate zones.

Epicuticular Wax1 Secretion in Diapause and Non-diapause Pupae of the Bertha Army worm3

The epicuticular wax of diapausing and non-diapausing pupae of Mamestra configurata Walker was studied by chloroform extraction and thin layer chromatography. Diapausing pupae have twice as much wax as non-diapausing pupae (8-10 days old). The period of wax secretion in diapausing pupae was twice as long (8 days) as that of non-diapausing pupae (4 days). In addition, the diapausing pupae had 3 times as much hydrocarbons as non-diapausing pupae. Wax secretion was retarded in pupae stored at 5° and 0°C. Apparently, the thicker wax layer in general and the higher content of hydrocarbons in particular protect the diapausing pupae from desiccation during diapause.

SURVIVAL AND REPRODUCTIVE CAPACITY OF THE TOBACCO BUDWORM,HELIOTHIS VIRESCENS(LEPIDOPTERA: NOCTUIDAE), IRRADIATED AS DIAPAUSING AND YOUNG NONDIAPAUSING PUPAE

AbstractPupal survival, mating, and sperm transfer in tobacco budworms,Heliothis virescens(F.), irradiated as diapause pupae, decreased proportionately with increasing doses of 3, 5, and 7.5 krad. Also, the fertility of tobacco budworms irradiated as nondiapause pupae and of the F1progeny of such males decreased with increasing dose. When the female partner received eupyrene sperm, insects irradiated while the pupae were in diapause were fertile as were their progeny. Therefore, it does not appear plausible to irradiate diapause pupae of our strain of tobacco budworms to obtain sterile insects for a release program.

Hydrocarbons in the surface lipids of pupal tobacco budworms, Heliothis virescens

The surface lipids from pupae of the tobacco budworm, Heliothis virescens, had five homologous series of alkanes. Normal alkanes from 17 to 34 carbon atoms comprised 33% of the alkanes; heptacosane was the major constituent at 11%. Monomethylalkanes comprised 50% of the alkanes and consisted of terminally branched 2- and 3-methylalkanes and internally-branched components. The 9-, 11-, 13-, and 15-methylhentriacontane isomers were the major constituents at 24%. Dimethylalkanes from 33 to 35 carbon atoms comprised 14% of the alkanes. One GLC peak was tentatively identified as a mixture of 11,19- and 13,21-dimethyltritriacontane. Analyses of the hydrocarbons of four strains of pupae showed no difference in the type of hydrocarbons found in the cuticular surface lipids. However, a non-tanning body mutant of one strain did show an increase in the amount of hydrocarbon present. There was no difference in the amount of cuticular surface lipid on diapausing pupae compared with that on non-diapausing pupae. Furthermore, there was no difference in the amount of cuticular surface lipid on male pupae when compared with female pupae in both diapausing and non-diapausing stages of development.

The influence of temperature on respiration of diapausing pupae of Pieris brassicae (Lepidoptera)

The respiration of diapausing Pieris pupae has been measured at different temperatures between 5 and 35°C in animals maintained at 20°C, either 14 or 74 days after larvo-pupal ecdysis or at 5°C for 30 or 60 days. The sudden transfer of animals from 5 to 15, 20, 25, 30, 35°C or from 20 to 30, 35°C results in a respiratory overshoot whose characteristics (duration, height, extra-respiration) depend on experimental conditions. After a certain period of acclimation, overshoots are eliminated. The respiratory rate except for animals maintained during 74 days at 20°C can then be represented as an exponential function of temperature. The Q 10 values change according to the treatment given to pupae. The respiratory rate of male pupae is higher than that of female ones. The following points are discussed: 1. 1.|The meaning of overshoots is analysed according to economy and metabolic homeostasis, showing the existence of acclimation. 2. 2.|Exponential curves which are not relevant to non-diapausing pupae or to the diapausing ones taken at larvo-pupal molting are characteristic of steady metabolism. These curves can be interpreted as the result of the temperature effect on a master respiratory reaction which would then be rate limiting. 3. 3.|Wintering leads to gradual and slow adaptation to cold temperatures which brings both a respiratory increase, a decrease of the Q 10 and of the activation energy of the master reaction.

Tolerance of the diapausing stages of four species of Lepidoptera to methyl bromide

The diapausing stages exposed to methyl bromide were larvae of Ephestia elutella (Hübner) and Plodia interpunctella (Hübner), pupae of Pieris brassicae (L.) and eggs of Bombyx mori (L.). Diapausing larvae of Ephestia elutella were highly tolerant, a few surviving to the adult stage after exposure to concentration-time (CT) products of up to 150 mg hr/l at 25°C and 260 mg hr/l at 15°C. Diapausing larvae of Plodia interpunctella were tolerant at low temperatures but quite susceptible at 25°C. In both species, larvae in diapause were four to six times more tolerant than other larvae at 15°C or below, and strains recently collected from the field were more tolerant than laboratory reared stocks. In E. elutella, differences in the method of induction, maintenance or termination of diapause did not affect tolerance to fumigation. P. interpunctella larvae reared at high population density were more susceptible than those reared at low density. Among strains of these species, a correlation was observed between the duration of larval diapause and tolerance to methyl bromide. Adults emerging after fumigation of diapausing larvae were of lowered fertility but rarely sterile. The CT products required for the complete control of moths in diapause were higher than those currently recommended for the disinfestation of stored products. Diapausing pupae of an outdoor species Pieris brassicae required the very high CT product of 403 mg hr/l for complete control at 25°C and were at least six times more tolerant than non-diapausing pupae. Diapausing eggs of Bombyx mori required 179 mg hr/l for complete control, while non-diapausing eggs were all killed by 125 mg hr/l.

Bionomics of Euarestoides acutangulus (Diptera: Tephritidae)1

Information on the life cycle of Euarestoides acutangulus (Thomson), including observations on feeding and reproductive behavior, is presented. The fly is bivoltine in central coastal California, with overwintering occurring as diapausing pupae. Eggs were laid in the staminate florets of the host plant, Ambrosia chamissonis (Lessing) Greene (Compositae), and hatched in 4 days. Larvae fed upon the anthers of unopened florets. The amount of damage caused to a staminate head depended upon the number of larvae reaching maturity and the number of florets within the head. Larvae generally completed development in 23 days. Pupation occurred among the destroyed florets. The pupal period of non-diapausing pupae required 12 days.

Larval development of the rodent botfly, Cuterebra tenebrosa, in bushy-tailed wood rats and its relationship to pupal diapause.

Rodent botflies, Cuterebra tenebrosa Coquillett, were reared through several generations in bushy-tailed wood rats (Neotoma cinerea) in the laboratory. Eggs hatched in 10 days. Thirty-five days were required for complete larval development, with the first and second larval molts occurring at 9 and 19 days, respectively. Mature larvae formed puparia within 24 h after exit from host. Pupation look place 8 days later and diapausing characters were visible on the 12th post-exit day. Larvae from wood rat hosts kept on a long daylenglh ([Formula: see text] light) gave rise to a high percentage of non-diapausing pupae. Larvae reared on short daylengths produced diapausing pupae. Non-diapausing pupae emerged in 52 days, whereas diapausing pupae required up to 2 years to emerge. Attempts to terminate pupal diapause via temperature or photoperiod manipulation were unsuccessful.

Wax secretion in non-diapausing and diapausing pupae of the tobacco hornworm, Manduca sexta

Scanning electron microscopy of the epicuticle of the tobacco hornworm, Manduca sexta, showed that pupae in diapause possess thicker wax layers than non-diapausing pupae. Extractions of the epicuticle with CHCl 3 established that diapausing pupae secreted over three times as much wax as non-diapausing pupae, and that the total period of wax secretion in diapausing pupae was two to three times longer than that of non-diapausing pupae. Apparently, the extra thickness of the wax layer of diapausing pupae protects the insect from desiccation during diapause. The deposition of additional wax may result from hormonal changes accompanying entry into diapause.

PHOTOPERIODIC CONTROL OF DEVELOPMENT AND PHENOTYPE IN A SUBARCTIC POPULATION OF PIERIS OCCIDENTALIS (LEPIDOPTERA: PIERIDAE)

AbstractPieris occidentalis nelsoni W. H. Edwards from Fairbanks, Alaska, was reared under a variety of photoperiod–temperature regimes. The source population is presumably univoltine and monophenic, with a phenotype resembling the vernal one produced by multivoltine, diphenic P. o. occidentalis Reakirt in Colorado and California. Photoperiods of 10 or 15 h produced 100% diapause pupae at 15 °C and circa 65% at 25 °C. Under continuous light 22% diapaused at 15 °C and < 1% at 25 °C. About 20% of non-diapause pupae produced adults resembling the estival phenotype of P. o. occidentalis, which is unknown in wild P. o. nelsoni. Although nelsoni is more likely to diapause than the nominate subspecies from the Sierra Nevada, its potential for direct development and polyphenism is interpreted as evidence that it is derived from a multivoltine ancestor.