Photoperiodic Induction Of Diapause Research Articles

Tufted Apple Budmoth (Lepidoptera: Tortricidae): Photoperiodic Induction of Larval Diapause and Stages Sensitive to Induction 1

A photoperiodically controlled larval diapause of the short-day, long-day type was identified in tufted apple bud moth, Platynota idaeusalis (Walker). Pupae obtained from diapause and nondiapause larvae reared at 21°C were similar in weight; however, heart rates of diapause larvae were significantly lower than those of nondiapause larvae. Induction of larval diapause was dependent upon both photoperiod and temperature. The critical short-day photoperiod at 21°C was between 1 and 3 h for a Pennsylvania strain. The long-day critical photoperiod at 21°C was ca. 14 h for both Pennsylvania and North Carolina strains. Diapause at a short daylength was averted entirely at 32°C in a Pennsylvania strain. There was no difference in the incidence of diapause in progeny of adults and eggs reared under naturally decreasing short daylengths versus a constant daylength. Sensitivity to a diapause-inducing photoperiod did not occur at any one particular stage in larval development. A maximum of 39% diapause occurred when four of the five larval instars were exposed to a short daylength, and 100% diapause occurred when all five instars were exposed to a short daylength.

Photoperiodic induction of diapause in normal and allatectomized precocious pupae of Papilio machaon

Diapause in the swallowtail, Papilio machaon occurs at the pupal stage in response to short days during larval development. The precocious pupae obtained by allatectomy also entered diapause in response to short days. The photoperiodic induction of diapause in precocious pupae was very similar to that in normal pupae in spite of the abbreviation of the last-larval instar. The critical photoperiod for diapause in the precocious pupae was 14.5 h, being about the same as that in normal pupae. Occurrence of diapause in the swallowtail is closely associated with the pupal stage and the induction process may be triggered by the cessation of juvenile hormone secretion.

Photoperiodic time measurement in the spider mite Tetranychus urticae: A novel concept

To explain photoperiodic induction of diapause in the spider mite Tetranychus urticae a new theoretical model was developed which took into account both the hourglass and rhythmic elements shown to be present in the photoperiodic reaction of these mites. It is emphasized that photoperiodic induction is the result of time measurement as well as the summation and integration of a number of successive photoperiodic cycles: the model, therefore, consists of separate ‘clock’ and ‘counter’ mechanisms. In current views involvement of the circadian system in photoperiodism is interpreted in terms of the hypothesis that the photoperiodic clock itself is based on one or more circadian oscillators. Here a different approach has been chosen as regards the role of the circadian system in photoperiodism: the possibility, previously put forward by other authors, that some aspect of the photoperiodic induction mechanism other than the clock is controlled by the circadian system was investigated by assuming a circadian influence on the photoperiodic counter mechanism. The derivation of this ‘hourglass timer oscillator counter’ model of photoperiodic induction in T. urticae is described and its operation demonstrated on the basis of a number of diel and nondiel photoperiods, with and without light interruptions.

Carotenoids Function in Photoperiodic Induction of Diapause in a Predacious Mite

Predacious mites fed for two generations solely on the eggs of wild-type spider mites responded normally to short day lengths by entering diapause. However, predacious mites fedfor two generations on eggs of albino spider mites, which are completely devoid of carotenoids, did not respond to short-day photoperiods. Apparently carotenoids are essential for photoperiodic induction; possibly a carotenoid or carotenoid derivative functions as the photopigment concerned in photoperiodic light reception in these mites.

Dynamics of an Isolated Population of Aedes Triseriatus (Diptera: Culicidae): II. Factors affecting productivity of immature stages1

A discrete population of Aedes triseriatus was studied in a 10-ha oak woodlot containing 108 tree holes. Markrelease-recapture methods showed a population of 1225 adult females in late summer of 1975 (Sinsko & Craig 1978). In studies of immature stages, the period from hatching to pupation was 9 weeks in the spring but considerably shorter in midsummer. The sex ratio was distorted in favor of males in the spring, approached 1:1 in midsummer and then increased in favor of females at the end of the season. Tree hole productivity varied markedly, with 83% of pupae coming from 23% of tree holes. Photoperiod-induced diapause prevented all egg hatching after 3 August 1975; at this time, the photoperiod was 14L:10D.

Functional involvement of carotenoids in photoperiodic induction of diapause in the spider mite, Tetranychus urticae

ABSTRACT. Using pigment mutants in which the uptake and oxidative metabolism of β‐carotene is disturbed, it could be shown that carotenoid pigments are functionally involved in the photoperiodic reaction in the spider mite, Tetranychus urticae Koch (Acari; Prostigmata). Diapause responses appeared to be lowered in four albino mutants in comparison with the wild‐type strains from which they originated. Back‐crossing of the albino mutants to wild‐type for ten generations did not restore the capability to diapause. Selection for diapause for six generations also proved unsuccessful in increasing the diapause response of the albino strains. On the other hand, albino mites coming from hybrid (phenotypically wild‐type) mothers all diapaused normally. Apparently a maternal effect is responsible for the complete induction of diapause in albino mites. It is supposed that minimal amounts of carotenoids of maternal origin suffice in the embryo for the formation of a photopigment concerned in the photoperiodic induction of diapause. In albino mites the normal transmission of carotenoids via the egg is probably blocked. This transmission of pigment seems to be restored when the albinos originate from hybrid mothers, which possess the wild pigmentation.

OCCURRENCE OF A TWO GENERATION STRAIN OF THE EUROPEAN CORN BORER, OSTRINIA NUBILALIS (LEPIDOPTERA: PYRALIDAE), IN QUEBEC

AbstractThere are now two strains of the European corn borer, Ostrinia nubilalis (Hübner), in Quebec. The strain normally found produces one generation while the more recently introduced strain produces two generations per year. Both strains have been characterized and compared with corn borer strains from Ontario and New York State. The two attributes of the recently introduced strain that promote the development of a second generation are (1) early emergence in the spring with less intense diapause and (2) a lower critical photoperiod for diapause induction. The latter characteristic allows pupation of first generation larvae. Field and laboratory tests on the pheromone response of adult male moths demonstrated that the origin of this recent introduction was New York State.

Notes on the Biology and Diapause Inducement of the Hyperparasite Gelis tenellus

Gelis tenellus (Say) is one of the most abundant hyperparasites of the gypsy moth parasite Apanteles melanoscelus (Ratzburg). The mean developmental time of G. tenellus was 17 days at 25°C and 30% RH, and adults lived ca. 40 days. Adults remained reproductive for the initial 4/5 of their life span. Oviposition peaked at days 6-10. The major diapause inducing factor was photoperiod. The critical photoperiod for diapause induction was 11-14 h of daylight but diapause incidence never fell below 30%, even at 20-h photoperiod.

Evidence for the functional involvement of carotenoids in the photoperiodic reaction of spider mites.

PHOTOPERIODISM in insects and mites depends on the presence of light-absorbing pigments, which are probably located in the central nervous system; photoperiodic responses are mediated by the direct action of light on these nervous elements1. Until now, pigments involved in photoperiodic processes such as diapause and polymorphism have not been identified. Different groups of pigments have been named by various authors as possible candidates for this function. A biologically active role based mainly on action spectra studies and the absorption characteristics of isolated pigments has been suggested for pterins2, carotenoids3, a combination of carotenoproteins, flavoproteins and haemoproteins4 and bile pigments5. Carotenoids, pterins and flavins have also been proposed as possible photoreceptor pigments in studies on the spectral sensitivity of circadian rhythms6. According to Lees1, however, the usefulness of action spectra in identifying the light acceptor is limited, as spectra for photoperiodic action cannot at present be matched against absorption curves. A different approach was used by Zimmerman and Goldsmith7, who reared Drosophila on a carotenoid-free diet and showed that in one generation the sensitivity of the visual receptors was lowered by 3 log units because of lack of rhodopsin. At the same time the photosensitivity of the rhythm of pupal eclosion in the cultures was not affected, from which it was concluded that the pigment involved in mediating light effects on the circadian rhythm in Drosophila is not a carotenoid derivative. We demonstrate here that carotenoids are functionally involved in the photoperiodic induction of diapause in the spider mite Tetranychus urticae using a method involving pigment mutants.

The sensitivity of larval Plodia interpunctella and Ephestia elutella (Lepidoptera) to light during the photoperiodic induction of diapause

ABSTRACT. The incidence of diapause in larvae of Plodia interpunctella and Ephestia elutella held under two light systems was examined. Both systems progressively shortened the photophase of 24‐h cycles, one with a motorized dimming switch providing dawns and dusks about 1 h long, the other switching the lights instantaneously. The mean critical photoperiod for P. interpunctella was about 131/4 h and for E. elutella just over 14 h. In both species light intensities as low as 0.2 lx influenced the induction of diapause. In P. interpunctella the critical photoperiod and sensitivity to light were similar at 23.±.;5°C and 20.5±0.5°C. At 22.5°C the percentage of diapausing larvae of E. elutella increased from 2% in long photoperiods (> 15 h light), to 100% in short photo‐periods (t 12.5h light). Fox P. interpunctella, at 22.5°C the percentage increased from zero in long photoperiods (> 14 h light) to about 98% in short photoperiods (< 11.5h light), and at 20°C from 12% to 100% over a similar photoperiodic range. Similar results were obtained under selected fixed photoperiods, switched on or off instantaneously.

Occurrence of Larval-Pupal Intermediates in Hybrid Pink Bollworms1 Reared at Low Temperatures

In a study of the genetics of insect diapause, crosses were made between a nondiapausing strain of the pink bollworm, Pectinophora gossypiella (Saunders), from southern India and a diapausing strain from Arizona (U.S.A.). About 4% of the hybrid larvae, when reared in a diapause-inducing photoperiod (12 h light/day) and a temperature of 18°C, failed to undergo normal pupation but remained predominantly as larvae with patches of darkened and sclerotized pupal cuticle on the thorax and abdomen. All the affected insects died as larvalpupal intermediates. The symptoms seemed to reflect a disturbance in the balance between juvenile hormone and ecdysone, with the juvenilizing effect being predominant. It is believed that normal larval diapause may be regulated, at least in part, by activity of the corpus allatum that secretes juvenile hormone, whereas the prothoracic glands that secrete ecdysone are inactive. It is suggested that the hormonal condition of the abnormal hybrids was probably somewhat intermediate between that of a diapausing and a nondiapausing larva, and further studies of such developmental anomalies may help to elucidate the hormonal mechanism that regulates insect diapause.

The circadian eclosion rhythm inSarcophaga argyrostoma: Some comparisons with the photoperiodic “clock”

1. The pupal eclosion rhythm imSarcophaga argyrostoma was compared with the photoperiodic induction of diapause in the same species. The eclosion rhythm is controlled by a circadian system which free-runs in continuous darkness (DD), after exposure to light/dark cycles (LD) or to continuous light (LL), with an endogenous period, τ, close to 24 h. InLD cycles photoperiod controls the rate of larval development, and which eclosion gates are used by the emerging flies. 2. Sequential transfer of cultures fromLL to DD, or exposure to a 7 h delay in the light cycle at different ages, showed that the response (in terms of initiation and phase control of the eclosion rhythm) was maximal with young larvae, less with older larvae, and only marginal with the early intra-puparial stages. Older intrapuparial stages (developing adults) appear to show a renewed responsiveness to light pulses. 3. Phase response curves for the eclosion rhythm were “weak” or Type 1 with 1 h pulses; those for 8 h and 12 h pulses were “strong” or Type 0. After light periods in excess of about 12 h the eclosion peaks occurred at characteristic time (11.3+modulo τ h) after the light-off or “dusk” signal, provided that theLD cycles were experimentally discontinued before the end of larval development. 4. Cultures transferred fromLL into a dark (D) and a final light (L) period which together added up to a value (D+L) close to 24 or 48 h gave rise to highly rhythmic eclosion patterns. Those in whichD + L values were close to 36 or 60 h, however, were far less coherent. This difference is attributed to the multi-oscillator construction of the circadian system, and its internal temporal organisation. 5. A phase response curve for the photoperiodic oscillator was determined for 15 min resetting pulses by the use of 3-point “skeleton” photoperiods. Like the 1 h response curve for pupal eclosion, this was of the “weak” type with small “amplitude” phase changes. 6. The similarities between the eclosion rhythm and the photoperiodic oscillator inS. argyrostoma (same responsive period, same phase response curve, same phase relationships to driving light cycles) are discussed. The two systems are considered to be sufficiently alike for the overt system (eclosion) to be used as a measure of phase in the analysis of the photoperiodic clock, as recommended by Pittendrigh and Minis (1964).

Photoperiodic induction of the pupal diapause in the tobacco hornworm, Manduca sexta

A study was made of photoperiodic induction of the facultative pupal diapause in the tobacco hornworm, Manduca sexta, reared on artificial diet in the laboratory. The species entered a prolonged diapause when the egg and larval feeding stages were reared in daily photoperiods of 13·5 hr or less. Diapause was induced in all insects at photoperiods ranging from 1 to 13 hr, and part of the population entered diapause at only 15 to 30 min of light per day. Photoperiods of 14 hr or more and continous darkness prevented diapause. Duration of diapause varied with the inductive photoperiod in which the hornworms were reared during the sensitive period. Insects reared in longer diapause-inducing photoperiods within a range of 12 to 13·25 hr remained in diapause longer than those reared in shorter photoperiods. There was no difference in the rate of larval development of hornworms reared in diapause-inducing vs diapause-preventing photoperiods. Temperatures of 26 to 30°C were most favourable for the photoperiodic induction of diapause; at 21°C, the critical photoperiod and incidence of diapause were decreased. Diapause induction was suppressed by low (18°C) and higher (33°C) temperatures. The number of inductive 12L:12D (light = 12 hr; dark = 12 hr) cycles required to induce diapause ranged from as few as 5 for some insects to as many as 12 for others when the post-inductive régimen was continuous light, but with insects previously held in continuous dark, as few as 2 12L:12D cycles during the last 2 days of larval feeding induced diapause in 38 per cent of the population. Only 3 to 4 cycles of 15L:9D during the final larval instar reversed inductive effects of 14 to 15 12L:12D cycles. Photoperiodic sensitivity extended from the late embryo to the end of larval feeding but showed considerable fluctuation during development with maximum sensitivity occurring just before egg hatch and during larval growth. Light breaks applied at different times during the dark period of 12L:12D cycles generated different response curves, depending on the number of cycles in which light breaks were repeated. When repeated for 6 cycles, a unimodal response curve was obtained; 10 cycles produced a bimodal curve and light breaks given for 18 cycles throughout the sensitive period averted diapause regardless of time of night applied. It is suggested that diapause is regulated by a photo- and thermolabile substance that accumulates during long nights (11 hr or more) and acts during the early pupal stage to inhibit the translocation and release of development-promoting neurosecretion from the brain.

THERMAL ACCUMULATIONS, DIAPAUSE, AND OVIPOSITION IN A CONIFER-INHABITING PREDATOR, CHRYSOPA HARRISII (NEUROPTERA)

AbstractThe adults of Chrysopa harrisii Fitch, which are not predaceous, overwinter in a state of reproductive diapause. During both the dormant and the reproductive periods they remain dark green, a colour apparently adapted to the species’ occurrence on conifers. Two to three generations per season are possible in the Ithaca, N.Y., area.At 75°F, which is the optimum constant temperature for development and survival, the time from oviposition to adult eclosion is 29 days. Theoretical thresholds for development of all stages are relatively high, between 50° and 57°F, and development from egg to adult requires 566 heat degree days.In the laboratory, the critical photoperiod for diapause induction is between LD 13:11 and LD 14:10; short days maintain diapause for approximately 45 days (at 75°F); long days terminate diapause. Both newly-emerged and reproductively-active adults are extremely sensitive to diapause-inducing photoperiods. In the field, all adults emerging on 5 September or later enter diapause and it appears that diapause induction in the Ithaca population begins in the latter part of August. Short days maintain diapause until the end of December, and neither long days, increasing day lengths, nor low temperatures play a role in hastening diapause termination in nature.In timing its vernal reproduction, C. harrisii has evolved a strategy that combines an early-ending diapause with an apparently relatively high temperature threshold for post-diapause development. Therefore, although diapause ends around the winter solstice, heat accumulation is prevented until much later, when temperatures are relatively high.

Photoperiodic Sensitivity of the Alfalfa Weevil During Larval Developmenet1

Larvae of Hypera postica (Gyllenhal) from the eastern United States were subjected to diapause-inducing photoperiods at various stages of development to study the relationship of photoperiod and larval development upon the induction of diapause in the adult weevil. Adults from larvae which were exposed to short-day photoperiods did not diapause, whereas adults from larvae exposed to long-day photoperiods did diapause. As little as 1 day of long-day photoperiod during larval development was sufficient to induce diapause in the adult. Adults from larvae which were subjected to an uninterrupted 16-hr photophase diapaused, whereas adults from larvae exposed to 16 hours of light which was interrupted by two 4-hour periods of scotophase did not diapause, and limited observations suggest that starvation of the larva in the late 3rd and 4th stages induced diapause in the adult.

Diapause and Polymorphism in California Populations of Psylla pyricola (Homoptera: Psyllidae)1,2,3

Pear psylla, Psylla pyricola Foerster, from Wynola, San Diego County, California (approximately lat 33°5'N), could be induced to enter diapause by exposure to photoperiod of 14 hr light and 10 hr dark; but pear psylla from Danville, Contra Costa County, California approximately lat 37°50'N), required a photoperiod of13.5 hr light and 10.5 hr dark when both were reared identical temperatures. Females that entered diapausehad long forewings; females that did not enter diapause were short to long winged, and no females with short forewings entered diapause. At 16 and 27°C, the critical photoperiod for induction of diapause in females from Wynola differed only slightly. Females did not enter diapause when they were not exposed to the critical photoperiod until they had reached the 5th instar. Females from populations collected from several locations in California, north of Wynola, had similar mean lengths of forewing when reared under a 14.5-hr daily photoperiod. For males, the mean forewing lengths also were similar, but the forewings of males were always shorter than those of females. However, under the same rearing conditions, females and males from the Wynola population always had longer forewings than those from northern populations. In the field, during summer, mean length of the forewings increased much sooner at Wynola than at other locations. The difference may relate to the origin of the Wynola population.

Humoral and nervous pathways in photoperiodic induction of diapause in Leptinotarsa decemlineata

By means of microsurgical operations combined with photoperiodic treatment the rôle of the different elements of the neuro-endocrine system in the effects produced by long- and short-day induction is investigated. The effect of short day is explained by the inactivity of the medial protocerebral neurosecretory cells, resulting in a lack of activation of the corpora allata. Apparently, these glands need constant activation by the brain hormone. The innervation of the corpus allatum appears to play a rôle at the onset of diapause induction rather than in maintaining diapause. We have found no evidence in favour of an inhibitory ‘diapause hormone’, produced by either the brain or the suboesophageal ganglion. The effect of long day is explained by activation of the medial neurosecretory cells. The brain hormone can activate the corpora allata by way of the haemolymph with the same speed as via the corpora cardiaca. Implanted corpora allata without any nervous connexions can be activated and inactivated repeatedly by manipulating the photoperiod. In producing the behavioural components of photoperiodic response, the corpus allatum does not act by way of the ovaries.

Photoperiodic induction of diapause in larvae of the winter tick, dermacentor albipictus.

Laboratory-reared females of Dermacentor albipictus (Packard) were held in photoperiodic regimes of ¼, 8, 12, and 16 hours light per 24-hour period at 27°C and 80% RH for oviposition, and their eggs and resulting larvae were retained in these regimes. Samples of these larvae were removed every 2 weeks and placed on guinea pigs to determine the rate of attachment. Those larvae held in the 8-hr photophase attached and fed when they were 4 weeks old and at all subsequent 2-week intervals; these nondiapausing larvae also attached to a Hereford steer and developed to engorged females from which viable eggs were collected. Larvae in the 12-hr photophase remained in diapause for 10 weeks; those in the ¼- and 16-hr photophases remained in diapause for 12 weeks. D. albipictus is therefore a short-day arthropod with a facultative diapause in the larval stage.

Environmental factors controlling the induction of diapause in the pink bollworm, Pectinophora gossypiella (Saunders)

Fourth instar larvae of the pink bollworm may undergo a facultative diapause at the end of the larval feeding period. Diapause larvae are heavier, have a slower rate of heart beat, and consume oxygen at about one-sixth the rate of non-diapause individuals. In addition, the diapause condition is accompanied by an atrophy of the male gonads and an increase in fat content of both sexes. Diapause in the pink bollworm is primarily under the control of the photoperiod. With the strain of moths used in this study, day lengths of 13 hr or less induced diapause whereas longer day lengths averted this condition. Diet and temperature may also exert an effect on the percentage of the population that enters diapause; however, these effects are not readily apparent except under short days. Under inductive photoperiods the greatest incidence of diapause in the pink bollworm occurred in populations reared under the coolest temperatures on diets having the greatest oil content. A possible thermoperiodic effect of lowered temperatures during the scotophase was demonstrated. The pink bollworm appears to respond to absolute rather than changing day lengths. Although the early larval instars appear to be most sensitive to diapause-inducing photoperiods, diapause may be induced in some individuals in any instar. Furthermore, the effects of short-day exposure in the early instars may be largely nullified by exposure of the subsequent instars to long days.

Versuche über den Zeitmeßvorgang bei der photoperiodischen Diapause-Induktion von Pieris brassicae

With three different methods no significant influence of temperature on the timing process in photoperiodic diapause induction of Pieris brassicae was detectable. Between 15 and 21°C the physiological status in which light strongly inhibits diapause is always reached about 14 -16 hours after the beginning of the daily light period. The diurnal changes in responsiveness to light correspond to diurnal changes in the volume of the corpora allata.