The Experts below are selected from a list of 4146 Experts worldwide ranked by ideXlab platform
Wen Qi Rosen - One of the best experts on this subject based on the ideXlab platform.
-
the circadian rhythm of the sex pheromone mediated behavioral response in the turnip moth agrotis segetum is not controlled at the peripheral level
Journal of Biological Rhythms, 2003Co-Authors: Wen Qi Rosen, Guibiao Han, Christer LofstedtAbstract:The pheromone-mediated upwind flight of male turnip moths was observed in a flight tunnel at different times of day under conditions of a light-dark (LD) cycle, constant darkness (DD), and a shifted photoperiod. Under both LD and DD conditions, a significantly larger number of males flew to the pheromone during both the scotophase and the subjective scotophase than during the Photophase and the subjective Photophase for 2 consecutive days. When 1-day-old moths were transferred to a shifted LD cycle with lights turned off 4 h earlier, male behavioral responses to the pheromone advanced in time accordingly by 4 h. This showed that male behavioral responses to the pheromone are under the control of an endogenous oscillator. To further examine the level at which the circadian rhythm of the male behavioral response is regulated, the authors tested the olfactory responses of male antennal receptors to pheromone stimuli by means of electroantennograms (EAG) at different times of day. No significant variation in the sensitivity of the male antennal response to the pheromone was observed in terms of time of day. The results suggest that circadian regulation of the rhythmic behavioral response to pheromones in the male Agrotis occurs at the central nervous system level.
-
endogenous control of circadian rhythms of pheromone production in the turnip moth agrotis segetum
Archives of Insect Biochemistry and Physiology, 2002Co-Authors: Wen Qi RosenAbstract:The circadian variation of pheromone production in the turnip moth, Agrotis segetum, was characterized by quantifying (Z)-7-dodecenyl acetate (Z7-12:OAc), the most abundant pheromone component produced by female turnip moth, at different times of day. Under 17:7 h light-dark cycle (LD), the peak of Z7-12:OAc production occurred around 4 h into the scotophase, while there was very little pheromone production during the Photophase. When females were maintained under constant darkness (DD), the periodicity of pheromone production was sustained for 3 consecutive days. Furthermore, the rhythm in pheromone production could be entrained to a shifted LD. These results demonstrate that the pheromone production in the turnip moth is regulated endogenously by a circadian clock. To understand how the circadian rhythm of pheromone production is generated, circadian variation of pheromone- biosynthesis-activating neuropeptide (PBAN)-like activity in the brain-suboesophageal ganglion complexes (Br-SOG), hemolymph, and ventral nerve cord (VNC) was also examined. Under both LD and DD, only the VNC displayed a circadian variation in the PBAN-like activity, which was significantly higher during the late-Photophase than that in the scotophase. In addition, the present study showed that removal of VNC in isolated abdomen did not affect PBAN stimulation of pheromone production, while severing the VNC impaired normal pheromone production. The role of Br-SOG, VNC, and hemolymph in the regulation of the periodicity of pheromone production is discussed.
Christer Lofstedt - One of the best experts on this subject based on the ideXlab platform.
-
the circadian rhythm of the sex pheromone mediated behavioral response in the turnip moth agrotis segetum is not controlled at the peripheral level
Journal of Biological Rhythms, 2003Co-Authors: Wen Qi Rosen, Guibiao Han, Christer LofstedtAbstract:The pheromone-mediated upwind flight of male turnip moths was observed in a flight tunnel at different times of day under conditions of a light-dark (LD) cycle, constant darkness (DD), and a shifted photoperiod. Under both LD and DD conditions, a significantly larger number of males flew to the pheromone during both the scotophase and the subjective scotophase than during the Photophase and the subjective Photophase for 2 consecutive days. When 1-day-old moths were transferred to a shifted LD cycle with lights turned off 4 h earlier, male behavioral responses to the pheromone advanced in time accordingly by 4 h. This showed that male behavioral responses to the pheromone are under the control of an endogenous oscillator. To further examine the level at which the circadian rhythm of the male behavioral response is regulated, the authors tested the olfactory responses of male antennal receptors to pheromone stimuli by means of electroantennograms (EAG) at different times of day. No significant variation in the sensitivity of the male antennal response to the pheromone was observed in terms of time of day. The results suggest that circadian regulation of the rhythmic behavioral response to pheromones in the male Agrotis occurs at the central nervous system level.
Maroudio Kentouri - One of the best experts on this subject based on the ideXlab platform.
-
enhanced biological performance of intensive sea bream sparus aurata larviculture in the presence of phytoplankton with long Photophase
Aquaculture, 2002Co-Authors: Nikos Papandroulakis, Pascal Divanach, Maroudio KentouriAbstract:Abstract Sea bream larvae were reared under intensive conditions either with (pseudo-green water technique) or without (clear water technique) the addition of phytoplankton in the rearing tanks, under 24- or 18-h Photophases. Phytoplankton presence in the rearing medium resulted in 44±17% survival and individuals of 2.0±0.2 mg wet weight after 20 days of rearing. With the clear water method, both survival and growth decreased to 16±6% and 1.1±0.2 mg, respectively. The daily consumption rate (as milligram of carbon consumed per milligram body carbon) at the beginning of exogenous feeding was 0.5 day −1 for all experimental conditions. At later stages, individuals reared with phytoplankton present had a daily consumption rate of about 0.7 day −1 , while those reared with the clear water technique presented consumption rates from 1.0 (for 24-h Photophase) to 1.9 day −1 (for 18-h Photophase). The mean food assimilation efficiency of the larvae, expressed as a Food Conversion Index (FCI), was between 6.3±1.4 (for 18-h Photophase) and 8.2±1.2 (for 24-h Photophase) for the individuals reared in the presence of phytoplankton. For larvae reared using the clear water technique, FCI was between 12.8±2.4 (for 24-h Photophase) and 20.1±5.3 (for 18-h Photophase).
-
bream sparus aurata larviculture in the presence of phytoplankton with long Photophase
2002Co-Authors: Nikos Papandroulakis, Pascal Divanach, Maroudio KentouriAbstract:Ž Sea bream larvae were reared under intensive conditions either with pseudo-green water .Ž . technique or without clear water technique the addition of phytoplankton in the rearing tanks, under 24- or 18-h Photophases. Phytoplankton presence in the rearing medium resulted in 44" 17% survival and individuals of 2.0 " 0.2 mg wet weight after 20 days of rearing. With the clear water method, both survival and growth decreased to 16 " 6% and 1.1" 0.2 mg, respec- Ž. tively. The daily consumption rate as milligram of carbon consumed per milligram body carbon at the beginning of exogenous feeding was 0.5 day y1 for all experimental conditions. At later stages, individuals reared with phytoplankton present had a daily consumption rate of about 0.7 day y1 , while those reared with the clear water technique presented consumption rates from 1.0 Ž. y1 Ž. for 24-h Photophase to 1.9 day for 18-h Photophase . The mean food assimilation efficiency Ž.
D S Joshi - One of the best experts on this subject based on the ideXlab platform.
-
bright Photophase accelerates re entrainment after experimental jetlag in drosophila
Naturwissenschaften, 2012Co-Authors: Boynao Sinam, Pooja Thakurdas, Shweta Sharma, D S JoshiAbstract:The efficacy of bright Photophase (BP) in accelerating the re-entrainment of Drosophila biarmipes rhythm following 8 h phase advance and delay of light–dark (LD) cycle was examined by subjecting the flies to 24 h LD cycles with dim Photophase (DP) at 30 lx and BP at 300 lx. Re-entrainment was analysed by using the activity onset, activity offset and the duration of activity. Following LD advance or delay, the BP flies re-entrained faster than the DP flies which was attributed to the enhanced zeitgeber strength of BP. Nevertheless, the re-entrainment was a protracted process even in the BP flies since the activity offsets underwent more transients than the activity onsets. Thus, this study demonstrates that the BP accelerates the re-entrainment in D. biarmipes. It, however, also reveals that the re-entrainment is a prolonged process when the activity onset and offset are regarded as the rhythm markers.
-
paradoxical masking effects of bright Photophase and high temperature in drosophila malerkotliana
Chronobiology International, 2012Co-Authors: Shweta Sharma, Pooja Thakurdas, Boynao Sinam, D S JoshiAbstract:Synergic contribution of light and temperature is known to cause a paradoxical masking effect (inhibition of activity by bright light and high temperature) on various rhythms of animals. The present study reports the paradoxical masking effects of 1000-lux Photophase at 25°C on the locomotor activity rhythm of Drosophila malerkotliana. Flies were subjected to light (L)-dark (D) 12:12 cycles wherein the Photophase was varied from 10 to 1000 lux, whereas the scotophase was set to 0 lux in these and subsequent LD cycles. At 10, 100, and 500 lux, the flies were diurnal; however, at 1000 lux they were nocturnal. Transfer from LD 12:12 cycles to continuous darkness (DD) initiated free-running rhythmicity in all flies. Free-running rhythms of the flies switched from the 10-lux to the 500-lux groups started from the last activity-onset phase of the rhythm following 3-5 transient cycles, suggesting involvement of the circadian pacemaker. In contrast, the free-running rhythm of the flies of the 1000-lux group began abruptly from the last lights-on phase of the LD cycle, indicating noninvolvement of the pacemaker. Furthermore, all flies showed nocturnal activity in the two types of LD 12:12 cycles when the Photophase was 1000 lux. The first type of LD cycles had three succeeding Photophases of 100, 1000, and again 100 lux, whereas the second type of LD cycles had only one Photophase of 1000 lux, but the LD 12:12 cycles were reversed to DL 12:12 cycles. Apparently, the combined effects of light and temperature caused such paradoxical masking effects. This hypothesis was tested by repeating the above experiments at 20°C. Flies in all experiments exhibited a diurnal activity pattern, even when the Photophase was 1000 lux. Thus, the present study demonstrates that the paradoxical masking effect in D. malerkotliana was caused by the additive influence of light intensity and temperature. This strategy appears to have physiological significance, i.e., to shun and thus protect against the bright Photophase at high temperature in the field.
-
effects of Photophase and altitude on oviposition rhythm of the himalayan strains of drosophila ananassae
Chronobiology International, 2007Co-Authors: Moses K Satralkar, P V Khare, V L Keny, Vanlalnghaka Chhakchhuak, M S Kasture, A J Shivagaje, S B Iyyer, R J Barnabas, D S JoshiAbstract:The effects of varying Photophase and altitude of origin on the phase angle difference (Psi) of the circadian rhythm of oviposition during entrainment to light-dark (LD) cycles and the aftereffects of such Photophases on the period of the free-running rhythm (tau) in constant darkness (DD) were evaluated in two Himalayan strains of Drosophila ananassae, the high-altitude (HA) strain from Badrinath (5,123 m above sea level=ASL) and the low-altitude (LA) strain from Firozpur (179 m ASL). The Psi (i.e., the hours from lights-on of the LD cycle to oviposition median) of both strains was determined in LD cycles in which the Photophase at 100 lux varied from 6 to 18 h/24 h. The HA strain was entrained by all LD cycles except the one with 6 h Photophase in which it was weakly rhythmic, but the LA strain was entrained by only three LD cycles with Photophases of 10, 12, and 14 h, but Photophases of 6, 8, 16, and 18 h rendered it arrhythmic. Lights-off transition of LD cycles was the phase-determining signal for both strains as oviposition medians of the HA strain occurred approximately 6 h prior to lights-off, while those of the LA strain occurred approximately 1 h after lights-off. The Psi of the HA strain increased from approximately 2 h in 8 h Photophase to approximately 11 h in 18 h Photophase, while that of the LA strain increased from approximately 11 h in 10 h Photophase to approximately 15 h in 14 h Photophase. The aftereffects of Photophase of the prior entraining LD cycles on tau in DD were determined by transferring flies from LD cycles to DD. The tau of the HA strain increased from approximately 19 to approximately 25 h when transferred to DD from LD 8:16 and LD 18:6 cycles, respectively, whereas the tau of the LA strain increased from approximately 26 to approximately 28 h when transferred to DD from LD 10:14 and LD 14:10 cycles, respectively. Thus, these results demonstrate that the Photophases of entraining LD cycles and the altitude of origin affected several parameters of entrainment and the period of the free-running rhythm of these strains.
Chobei Imai - One of the best experts on this subject based on the ideXlab platform.
-
photoperiodic induction and termination of summer diapause in adult epilachna admirabilis coleoptera coccinellidae from a warm temperate region
European Journal of Endocrinology, 2004Co-Authors: Chobei ImaiAbstract:In warm temperate and subtropical regions an adult summer diapause regulates the timing of oviposition. Epilachna admirabilis is a univoltine phytophagous lady beetle ranging from south to north Japan, Taiwan, China and Myanmar. In Japan the species hibernates in the full-grown larval stage. In cool temperate Sapporo (43°04´N) the adults never enter summer diapause but pass a second winter in diapause. This study revealed that in Kyoto (35°01´N), the adults had a summer diapause induced by an intermediate photoperiodic response; they had a critical photoperiod of approximately 14.5 h light per day. All females entered reproductive diapause under a long photoperiod of 16L (light) : 8D (dark) and 6.7% of them did so under shorter photoperiods of 13L : 11D and 12L : 12D. However, diapause incidence was 40% at 8L : 16D, suggesting the existence of a second critical photope- riod at a Photophase slightly less than 8 h. At Photophases of 12-15 h, non-diapausing females laid eggs on average between 27.1 to 39.0 days after emergence. Photoperiod reversibly regulated the induction, maintenance and termination of the adult diapause. Tem- peratures of 20-30°C did not affect the incidence and termination of diapause at 16L : 8D. Adult winter diapause at the higher lati- tude Sapporo might have originated from adult summer diapause at middle latitude regions such as Kyoto. Selection at increasing latitudes would have forced northerly populations of the species to lose the adult summer diapause in the range of natural day- lengths. Subsequent selection pressure should have favored adults that avoided futile oviposition in late summer or autumn, survived cold winters in diapause and commenced an additional oviposition in the second summer. Thus, a latitudinal difference in photoperi- odic responses might have developed.
