Diapause affects cuticular hydrocarbon composition and mating behavior of both sexes in Drosophila montana

Envipnmental cues,mainly photoperiod and temperature,are known to control female adult reproductive diapause in several insect species.Diapause enhances female survival during adverse conditions and postpones progeny production to the favorable season.Male diapause(a reversible inability to inseminate receptive females)has been studied much less than female diapause.However,if the males maximized their chances to fertilize females while minimizing their energy expenditure,they would be expected to be in diapause at the same time as females.We investigated Drosophila montana male mating bchavior under short-day conditions that induce diapause in females and found the males to be reproductively inactive.We also found that males reared under long-day conditions(reproducing individuals)court reproducing postdiapause fermales,but not diapausing ones.The diapausing fies of both sexes had more long-chain and less short-chain hydrocarbons on their cuticle than the reproducing ones,which presumably increase their survival under stressful conditions,but at the same time decrease their attractiveness.Our study shows that the mating behavior of females and males is well coordinated during and afier overwintering and it also gives support to the dual role of insect cuticular hydrocarbons in adaptation and mate choice.     

昆虫内分泌研究简况和中国的成就

<正> 昆虫内分泌学是昆虫生理学的重要分支之一。它研究昆虫的内分泌器官以及由相关器官组成的系统、昆虫的激素、昆虫激素的生理作用等。昆虫内分泌是20世纪中进展最快、成果较丰的领域之一。这个势头将要延续到21世纪。中国学者将沿着已往的成果前进。     

Juvenile hormone and moulting hormone titres in diapause- and non-diapause destined flesh flies

Failure of the brain to stimulate the prothoracic gland to release ecdysone has been widely regarded as the basis for diapause in insect pupae. In diapause-destined flesh flies, the absence of a peak of moulting hormone around the time of pupal head eversion supports this contention, but in addition, major pulses of juvenile hormone (JH) activity with a rhythmicity of 24 hr are unique to flesh flies destined for pupal diapause. JH activity persists during diapause, and a pulse of JH precedes the rise of moulting hormone that initiates adult development.     

Haemolymph ecdysteroid titres during larval-adult development in Rhodnius prolixus: Correlations with moulting hormone action and brain neurosecretory cell activity

A haemolymph ecdysteroid titre of the fifth (last)-larval instar of the hemipteran, Rhodnius prolixus has been determined by radioimmunoassay. During the last-larval stadium the ecdysteroid titre increases from a negligible level in the unfed insect to a detectable level within minutes following a blood meal. The titre reaches a plateau of ～50–70 ng/ml at 3–4 hr and this level is maintained until day 5–6, the time of the head-critical period in Rhodnius. At the head-critical period the titre begins to increase again, this time dramatically, reaching a peak of ～ 3500 ng/ml at day 13. From day 14 to ecdysis (day 21) the titre declines to a low level, ～ 30 ng/ml. Basal levels of ecdysteroids, ～ 15 ng/ml, were detectable in young adult males and females. A survey of haemolymph volumes during the last-larval instar indicates that the changes in the ecdysteroid titre reflect changes in the rates of ecdysteroid synthesis, and not changes in haemolymph volume. Excretion of ecdysteroids varies systematically during the instar, suggesting that control of ecdysteroid excretion may be important in regulation of the haemolymph titre. Qualitative analysis of the haemolymph ecdysteroid RIA activity revealed the presence of only ecdysone and 20-hydroxy-ecdysone. For the large peak preceding larval-adult ecdysis, 20-hydroxy-ecdysone was the predominant hormone. These results indicate that there may be two periods of release of prothoracicotropic hormone (PTTH) from the brain in Rhodnius, one immediately following the blood meal and the second on day 5 or 6. The significance of these times of PTTH release is discussed in relation to classical evidence of the timing of moulting hormone action, the response of target tissues, and with more recent findings on the timing of release of neurosecretory material from the brain of Rhodnius during moulting.     

EFFECT OF ECDYSTERONE ON VITELLOGENIN CONCENTRATION IN HAEMOLYMPH OF MALE AND FEMALE SARCOPHAGA BULLATA

Using Polyacrylamide gel electrophoresis, cycloheximide, incorporation of ³H-labelled amino acids and immunological methods, we have demonstrated that injection of ecdy- sterone induces de novo synthesis and release of vitellogenin in both sexes of Sarcophaga bullata. Vitellogenin concentrations were measured by the Mancini-radial immunodiffusion technique. In males a dose as low as 1 ng always makes vitellogenin appear in the haemolymph but very reproducible results are only obtained when doses varying from 10 to 250 ng were injected. In this range, the dose-response curve was linear on a semi- logarithmic scale.

In females, vitellogenin concentration remained low until a few hours after liver feeding and thereafter it rose sharply and reached its maximum about 24 h after the protein meal. 100 μg 6-hydroxydopamine HCl, injected before liver feeding in 4-day-old females, inhibited vitellogenin synthesis and yolk deposition, probably by interfering with the release of a brain hormone. This inhibitory effect on vitellogenin synthesis, but not that on yolk deposition, could be overruled by injection of ecdysterone. Juvenile hormone was ineffective on both. Females, ovariectomized on day 2 or 3, accumulated vitellogenin in their haemolymph, indicating that the continuous presence of the ovaries was not required for vitellogenin synthesis. The possible relation between the gonadotrophs hormone from the brain, vitellogenin synthesis and moulting hormone metabolism is discussed.     

Cyanoprotein: Developmental stage,sex and diapause-dependent expression,and synthesis regulation by juvenile hormone in the bean bug,Riptortus clavatus

Cyanoprotein (CP) synthesis was studied in nymphal and nondiapause adult, diapause adult, and juvenile hormone (JH) treated adult bean bugs, Riptortus clavatus. Hemolymph collected from bugs injected with [³⁵S]-methionine was analyzed by native polyacrylamide gel electrophoresis (PAGE) and fluorography, and CP synthesis was also determined quantitatively by rocket immunoelectrophoresis of hemolymph and counting. In the nymphal stages synthesis of CP-1, 2, 3, and 4 (with CP-4 synthesis predominant) reached a maximum at mid-instar and was not detected at each ecdysis, so that the synthetic activity of CPs changed cyclically in each instar. During the nymphal stages CP synthesis showed the same pattern and level in both females and males, and both diapause and nondiapause oriented bugs. In the adult stage, however, CP synthesis differed in the two sexes and nondiapause or diapause conditions. In nondiapause males CP synthesis was not detected in the adult, but in nondiapause females CP (only CP-1) was synthesized through the reproductive stages. CP-1 accumulated in the egg yolk together with vitellogenin. In diapause adults (both females and males) CP-1 to 4 were synthesized at a very low rate for over 2 months and accumulated in the hemolymph. JH or JH analog (JHA) methoprene and also long day condition, which terminate diapause, switched the main CP synthesis CP-4 to CP-1 in females. CP synthesis in diapause males stopped after JH(A) treatment. The activities of CP synthesis, thus, changed in developmental stages, sexes, and diapause. This is an excellent system for study of specific gene expression and switching controlled by insect hormones and sex. © 1992 Wiley-Liss, Inc.     

Thermal orientation of Anthonomus pomorum (Coleoptera: Curculionidae) in early spring

Abstract. The selection of habitats with favourable temperature by the apple blossom weevil Anthonomus pomorum (L.) is investigated in a temperature gradient arena with a range of approximately 0–15 °C. Single female and male weevils are tested in the arena 2, 4 and 6 days after termination of diapause, during photophase and during scotophase. During photophase, weevils of both sexes choose the warmest part of the temperature gradient arena, irrespective of the time elapsed after diapause. During scotophase, high temperature is favoured by male weevils, as well as by females 2 and 4 days after diapause. However, 6 days after termination of diapause, females show no thermal preference in the temperature gradient arena during scotophase, indicating that thermal choice of female A. pomorum in the scotophase changes with time after the termination of diapause. The results suggest that both sexes benefit from thermoregulation by habitat choice during photophase when the weevils are flight active and colonize apple trees.     

Ecdysteroids in the haemolymph and the ovaries of the firebrat Thermobia domestica (Packard) (Insecta,Thysanura): Correlations with integumental and ovarian cycles

Ecdysteroids were analysed with radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) in females of the apterygotous insect Thermobia domestica, which ahs overlapping moulting and reproductive cycles. During each moulting cycle, a peak in the haemolymph concentration of ecdysteroids occurs at day 9 (in the 11-day standard cycle), which can be correlated with apolysis and the beginning of new cuticle deposition. The ovaries show a peak of ecdysteroids at day 5 (i.e. one day before egg-laying), which suggests that these hormones are also involved in the reproductive cycle. In both cases, HPLC analysis combined with RIA suggests that the main ecdysteroid is 20-hydroxyecdysone. This duality in the function of ecdysteroids is discussed.     

Anteroposterior gradient during nymphal-adult moulting cycle of the tropical bont tick,Amblyomma variegatum (Acarina: Ixodidae)

Summary The structure of the extensible (alloscutum) and inextensible (scutum) integument of the nymph, Amblyomma variegatum was examined during the whole bloodmeal and the nymphal-adult moulting cycle. Integumental events were tentatively correlated with the ecdysteroid levels measured by radioimmunoassay. We observed that all the integumental events were realised along an anteroposterior gradient. During the 5 days corresponding to the bloodmeal, although the hormone concentration was low, a new endocuticle was deposited on both the alloscutum and scutum. Furthermore, mitoses were initiated in the capitulum. On days 1–2 after the meal, ecdysteroid titres began to increase and reached a first peak corresponding to 4.1 ng 20-hydroxyecdysone equivalents/tick on the 4th day after the ticks dropped off their host. At this time the epidermis of the capitulum was detached and the outline of the adult capitulum was already visible. Mitotic activity in the alloscutum was initiated. On day 6 post-drop, the frontal apolysis was achieved and the ecdysteroid titres declined to basal values. A second peak much higher than the first one (maximum value of 33.7 ng/tick) and identified principally as 20-hydroxyecdysone by HPLC/RIA was noted on the 13th day post-drop. During the period of increase in the ecdysteroid levels (days 9–10 post-drop), the mitotic phase ended in the alloscutum and the apolysis began. Epicuticle was deposited after day 12 postdrop. Then, while the titre fell to low values (about 1.6 ng/tick, days 16–20 post-drop), the exocuticle was deposited and the nymphal cuticle was digested. All adult structures were functional 3 days before ecdysis. In young male as in female adults the mean value of the ecdysteroid levels corresponded to about 2.5 ng/tick. Finally, hydrolysis of tick whole extracts with esterase demonstrated a low increase of RIA-positive material, demonstrating the probable presence of natural ecdysteroid fatty-acid conjugates in this species.     

Ecdysteroids and adult diapause in the Colorado potato beetle, Leptinotarsa decemlineata

ABSTRACT. The difference in ecdysteroid activity in short-day (10-h photo-phase) and long-day (16-h photophase) Leptinotarsa decemlineata Say adults was characterized by high performance liquid chromatography, which revealed that for short-day beetles ecdysterone and ecdysone are the major constituents of the free ecdysteroids, whereas in long-day beetles products co-migrating with 2-deoxyecdysone and 2-deoxyecdysterone are just as abundant. Ecdysteroids were detected (15 ng/ml) only in the haemolymph of females. Ligation experiments showed that the induction of the diapause syndrome by inactivation of the corpora allata or the brain not only resulted in the formation of the typical diapause proteins but also in an increase of the ecdysteroid activity. It is suggested that adult diapause in L.decemlineata is regulated by a multifactorial system.     

The molting hormone activity in Sarcophaga buttata in relation to metamorphosis and reproduction

Ecdysteroid levels were determined by radioimmunoassay, using an antiserum with higher affinity for ecdysterone than for ecdysone. In both sexes, the ecdysteroid level remains low until day 3 after eclosion. When fed liver on day 3, the ecdysteroid titre declines within 4 h in both sexes, stays low in males, but increases again after 12 h in females. The content in non-liver-fed animals, specially females, was significantly higher than if given liver. The level in liver-fed whole animals increased during oogenesis from the onset of follicular growth until the 4B—4C stage, and decreased thereafter.

During embryogenesis, a new high level was found in females, due to the developing embryos which contained a high titre. In isolated ovaries, the ecdysteroid content increased during follicular growth, with a steep increase during the last phase (4C—M and from M to uterine eggs). The ecdysteroid content in hemolymph of 7-day-old females, fed liver or not, was around 10 ng/ml, but in hemolymph of males of the same age no activity was found.

Ovariectomized females contained 12.4 ng/g ecdysteroid. The level during metamorphosis was also determined, mainly to be able to compare our radioimmunoassay results with known bioassay data. Our results support the statement that the ovary cannot be the only site of synthesis of molting hormone in adult S. buttata.     

Photoperiodism of diapause induction in Thyrassia penangae (Lepidoptera: Zygaenidae)

Thyrassia penangae enters winter diapause as a prepupa in a cocoon. Photoperiodism of diapause induction was systematically investigated in this moth. The photoperiodic response curves under 24-h light-dark cycles showed that this insect is a typical long-day species. The critical daylength was 13 h 30 min at 25 °C, 13 h at 30 °C and 12 h 20 min at 28 °C. Transferring experiments from a short day (LD 12:12) to a long day (LD 15:9) or vice versa indicated that photoperiodic sensitivity mainly occurs during the larval period. In experiments using non-24-h light-dark cycles, when the length of photophase exceeded the critical daylength (13.5 h), was diapause inhibited effectively, even when the length of scotophase exceeded the critical nightlength (10.5 h). Only when a long scotophase was combined with a short photophase, diapause was induced effectively. This result suggests that daylength measurement is more important than nightlength measurement in T. penangae. Night interruption experiments under 24-h light-dark cycles exhibited two points of apparent light sensitivity, but the photosensitive position was highly influenced by temperature and the length of scotophase. Nanda-Hamner experiments failed to reveal the involvement of a circadian system in this photoperiodic time measurement. All light-dark cycles from LD 12:12 to LD 12:72 resulted in a short day response, and all cycles from LD 14:4 to LD 14:72 resulted in a long day response, suggesting that photoperiodic time measurement in this moth is performed by a day-interval timer or an hourglass-like clock.     

Possible involvement of ecdysteroids in photoperiodically induced suppresion of ovarian development in a Japanese strain of the migratory locust,Locusta migratoria

In a Japanese population of Locusta migratoria, adult females become reproductively inactive under crowding and long days (LD) and reproductively active under crowding and short days (SD). The identity and titre of ecdysteroids in the haemolymph and ovaries from adult females reared under SD and LD were investigated by RIA/HPLC. The effects of exogenous juvenile hormone (JH) III treatments on the termination of such reproductive arrest and ecdysteroid contents in LD females were also examined. In general, ecdysteroid titres in both haemolymph and ovaries were significantly higher in reproductively active SD females than in reproductively inactive LD females. A clear difference was also observed in oocyte growth between SD and LD individuals. JH III applications (three consecutive topical applications, 150 μg per insect per day from day 3) stimulated ovarian development in LD females and significantly increased the haemolymph and ovarian ecdysteroids to a level comparable to that of reproductively active SD adult females.     

REPRODUCTIVE DIAPAUSE IN TYPHLODROMUS OCCIDENTALIS NESBITT (ACARINA: PHYTOSEIIDAE) FROM SOUTHERN NEW SOUTH WALES

Abstract
Studies on the reproductive diapause of an introduced insecticide-resistant strain of the phytoseiid predator, Typhlodromus occidentalis Nesbitt, from southern New South Wales are reported. Diapause was induced in 43–59% of predators when reared at 16 or 19°C under photophases of 10–12 h. No diapause induction response curve with changing photophase was evident. Diapause in overwintering predators was readily terminated by exposure to warm temperatures and a long photophase. The rapidity of diapause termination increased progressively during winter. The apparent loss of dependency upon reproductive diapause as an overwintering strategy in this strain of T. occidentalis is discussed.     

Diapause in the mite Metaseiulus occidentalis: Stages sensitive to photoperiodic induction

Stages of Metaseiulus occidentalis sensitive to photoperiod induction of diapause were determined by transferring various stadia into diapause-inducing conditions, and rearing them until adult females could be scored for reproductive condition. When eggs were transferred to 10 hr light at 19°C from 24 hr light at 25°C and the mites reared to adults, 92 per cent entered diapause. When larvae and all subsequent stages were kept under the inductive conditions, 62 per cent of adult females diapaused. Mites transferred as protonymphs into inductive conditions yielded only 10 per cent in diapause, and mites transferred as deutonymphs or newly emerged females did not enter diapause.However, adult females reared from eggs at 19°C under 12 hr light (which is near the critical photophase of 11·2 hr at 19°C) showed an unexpected sensitivity to photoperiod. Some newly emerged females oviposited upon transfer to an 8 hr photophase at 19°C. Some then stopped ovipositing and apparently entered diapause; these females resumed ovipositing after intervals ranging from 34 to 100 days. This was termed ‘switching’ into diapause. Some females reared under a 16 hr photophase at 19°C ‘switched’ also upon transfer as adults to shorter photophases—either 8 or 12 hr at 19°C. Thus, ‘switching’ may be due to transfer to shorter photophases. Promptness of mating vs delayed mating allowed ‘switching’ to be more easily detected.     

Thermoperiodic response and effect of photoperiod on thermoperiodic induction of diapause in Colaphellus bowringi

The effects of thermoperiods on diapause induction under continuous darkness (DD), continuous light (LL), and an L12:D12 photoperiod were investigated in the cabbage beetle, Colaphellus bowringi Baly (Coleoptera: Chrysomelidae), a short‐day species. Diapause could be induced by thermoperiod under both LL and DD; however, in the range of 24–30 °C, lower incidences of diapause were observed under LL than under DD. The critical cryophase was found to be dependent on the mean temperature of the thermoperiod applied. Although the thermoperiodic response pattern was similar under LL and DD, the incidence of diapause was higher under LL when the duration of the cryophase did not exceed 12 h. In contrast, when the duration of the cryophase was longer than 12 h, the incidence of diapause under LL was lower or equal to that under DD. When a thermoperiod of 24 °C (cryophase) and 28 °C (thermophase) was applied, the incidence of diapause was higher under LL than under DD, regardless of the duration of the cryophase. Thermoperiodic responses under a photoperiod of L12:D12 and under DD further revealed that induction of diapause was strongly influenced by the photophase temperature. Moreover, the incidence of diapause was lower when the thermophase coincided with the photophase than when the cryophase coincided with the photophase.     

Photoperiod and temperature studies to determine whether diapause is found in successive generations of the African phytoseiid,Euseius fustis (Pritchard and Baker) (Acari: Phytoseiidae)

Photoperiod and temperature conditions known to induce diapause in tropical arthropods were tested on two generations (G₀ and G₁) of the phytoseiid, Euseius fustis. Failure to lay eggs or a pre-oviposition period longer than 15 days were the criteria used to determine whether females were in diapause. Females reared from egg to adult and held throughout adult life under cyclic temperatures of 29/20°C in combination with long photophases of 16L: 8D and 14L: 10D showed no indication of aestival diapause. Similarly, hibernal diapause was not induced in females reared under a constant temperature of 18°C and a photophase of 8L: 16D. Under the various test conditions, females initiated oviposition within an average of 4 days. Overall, pre-oviposition patterns for G₀ and G₁ females were similar under the same test conditions. Reproductive patterns based on the mean number of eggs per female per day varied only slightly between generations for the same treatments. No behavioural or morphological attributes associated with diapause were observed.     

Effects of photoperiodically induced reproductive diapause and cold hardening on the cold tolerance of Drosophila montana

Coping with seasonal and daily variation in environmental conditions requires that organisms are able to adjust their reproduction and stress tolerance according to environmental conditions. Females of Drosophila montana populations have adapted to survive over the dark and cold winters at high latitudes and altitudes by spending this season in photoperiodically controlled reproductive diapause and reproducing only in spring/summer. The present study showed that flies of a northern population of this species are quite tolerant of low temperatures and show high seasonal and short-term plasticity in this trait. Culturing the flies in short day length (nearly all females in reproductive diapause), as well as allowing the flies to get cold hardened before the cold treatment, increased the cold tolerance of both sexes both in chill coma recovery time test and in mortality assay. Chill coma recovery time test performed for the females of two additional D. montana populations cultured in a day length where about half of the females enter diapause, also showed that diapause can increase female cold tolerance even without a change in day length. Direct linkage between diapause and cold tolerance was found in only two strains representing a high-altitude population of the species, but the phenomenon will certainly be worth of studying in northern and southern populations of the species with larger data sets.     

Effect of temperature and photoperiod on the induction of diapause in the mite Metaseiulus occidentalis

Diapause in a predaceous mite, Metaseiulus occidentalis, from a Californian vineyard population is a photoperiodically induced, facultative, adult reproductive diapause in females. The laboratory-determined critical photophase at 19°C was estimated at 11·2 hr. At 16°C, the critical photophase under laboratory conditions was approximately 11·6 hr. Temperature influenced the photoresponse of M. occidentalis so that diapause was entirely averted at temperatures of 22, 25, and 30°C. Aestival diapause at higher temperatures and long photophases was lacking. Development was continuous under constant darkness at all the temperatures tested. Diapause termination in laboratory-reared mites occurred spontaneously under the inductive conditions. Under constant 19°C temperatures, females responded to photophases so that diapause was terminated most rapidly under a 16 hr photophase (in 18·6 days); the 12 and 8 hr photophases, at this temperature, were next in their effectiveness, with 27·9 and 73·0 days, respectively, required for termination.