https://libjncir.jncasr.ac.in/xmlui/handle/10572/15 2026-04-04T05:31:08Z 2026-04-04T05:31:08Z Varma, Vishwanath Kannan, Nisha N. Sharma, Vijay Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2323 2017-02-21T10:23:52Z 2014-01-01T00:00:00Z

Selection for narrow gate of emergence results in correlated sex-specific changes in life history of Drosophila melanogaster Varma, Vishwanath; Kannan, Nisha N.; Sharma, Vijay Kumar Since the ability to time rhythmic behaviours in accordance with cyclic environments is likely to confer adaptive advantage to organisms, the underlying clocks are believed to be selected for stability in timekeeping over evolutionary time scales. Here we report the results of a study aimed at assessing fitness consequences of a long-term laboratory selection for tighter circadian organisation using fruit fly Drosophila melanogaster populations. We selected flies emerging in a narrow window of 1 h in the morning for several generations and assayed their life history traits such as pre-adult development time, survivorship, adult lifespan and lifetime fecundity. We chose flies emerging during the selection window (in the morning) and another window (in the evening) to represent adaptive and non-adaptive phenotypes, respectively, and examined the correlation of emergence time with adult fitness traits. Adult lifespan of males from the selected populations does not differ from the controls, whereas females from the selected populations have significantly shorter lifespan and produce more eggs during their mid-life compared to the controls. Although there is no difference in the lifespan of males of the selected populations, whether they emerge in morning or evening window, morning emerging females live slightly shorter and lay more eggs during the mid-life stage compared to those emerging in the evening. Interestingly, such a time of emergence dependent difference in fitness is not seen in flies from the control populations. These results, therefore, suggest reduced lifespan and enhanced mid-life reproductive output in females selected for narrow gate of emergence, and a sex-dependent genetic correlation between the timing of emergence and key fitness traits in these populations. Open Access

2014-01-01T00:00:00Z Menon, Anuj Varma, Vishwanath Sharma, Vijay Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2321 2017-02-21T10:23:54Z 2014-01-01T00:00:00Z

Rhythmic egg-laying behaviour in virgin females of fruit flies Drosophila melanogaster Menon, Anuj; Varma, Vishwanath; Sharma, Vijay Kumar Fruit fly Drosophila melanogaster females display rhythmic egg-laying under 12: 12 h light/dark (LD) cycles which persists with near 24 h periodicity under constant darkness (DD). We have shown previously that persistence of this rhythm does not require the neurons expressing pigment dispersing factor (PDF), thought to be the canonical circadian pacemakers, and proposed that it could be controlled by peripheral clocks or regulated/triggered by the act of mating. We assayed egg-laying behaviour of wild-type Canton S (CS) females under LD, DD and constant light (LL) conditions in three different physiological states; as virgins, as females allowed to mate with males for 1 day and as females allowed to mate for the entire duration of the assay. Here, we report the presence of a circadian rhythm in egg-laying in virgin D. melanogaster females. We also found that egg-laying behaviour of 70 and 90% females from all the three male presence/absence protocols follows circadian rhythmicity under DD and LL, with periods ranging between 18 and 30 h. The egg-laying rhythm of all virgin females synchronized to LD cycles with a peak occurring soon after lights-off. The rhythm in virgins was remarkably robust with maximum number of eggs deposited immediately after lights-off in contrast to mated females which show higher egg-laying during the day. These results suggest that the egg-laying rhythm of D. melanogaster is endogenously driven and is neither regulated nor triggered by the act of mating; instead, the presence of males results in reduction in entrainment to LD cycles. Restricted Access

2014-01-01T00:00:00Z Nikhil, K. L. Goirik, Gupta Ratna, Karatgi Sharma, Vijay Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2322 2017-02-21T10:23:40Z 2014-01-01T00:00:00Z

Role of Temperature in Mediating Morning and Evening Emergence Chronotypes in Fruit Flies Drosophila melanogaster Nikhil, K. L.; Goirik, Gupta; Ratna, Karatgi; Sharma, Vijay Kumar Following decades of research under controlled laboratory conditions, there has been growing interest in the recent past to study circadian rhythms in nature. Recent studies conducted under natural conditions have been fruitful in exploring several characteristics of circadian rhythms that remained cryptic and previously masked under standard laboratory conditions, reemphasizing that the complexity of circadian rhythms in nature increases multifold under the influence of multiple zeitgebers. However, our understanding of the contributions of different zeitgebers in shaping various rhythm characteristics still remains elusive. Previously, Vaze et al. reported that chronotype differences between the morning emerging (early) and evening emerging (late) populations of Drosophila melanogaster are considerably enhanced under natural conditions compared to standard laboratory conditions. In the present study, we assess the role of 2 primary zeitgebers in naturelight and temperatureindividually and in unison in driving chronotype differences. We report that when provided independently, temperature cycles enhance divergence between the early and late chronotypes more strongly than light, but when together, light and temperature appear to act antagonistically and that appropriate phase difference between light and temperature cycles is essential to promote chronotype divergence. Thus, our study highlights the importance of light and temperature, as well as their interaction with circadian clocks in mediating early and late chronotypes in fruit flies D. melanogaster. Restricted Access

2014-01-01T00:00:00Z Yadav, Pankaj Thandapani, Madhumohan Sharma, Vijay Kumar https://libjncir.jncasr.ac.in/xmlui/handle/10572/2320 2017-02-21T10:23:46Z 2014-01-01T00:00:00Z

Interaction of light regimes and circadian clocks modulate timing of pre-adult developmental events in Drosophila Yadav, Pankaj; Thandapani, Madhumohan; Sharma, Vijay Kumar Background: Circadian clocks have been postulated to regulate development time in several species of insects including fruit flies Drosophila melanogaster. Previously we have reported that selection for faster pre-adult development reduces development time (by similar to 19 h or similar to 11%) and clock period (by similar to 0.5 h), suggesting a role of circadian clocks in the regulation of development time in D. melanogaster. We reasoned that these faster developing flies could serve as a model to study stage-specific interaction of circadian clocks and developmental events with the environmental light/dark (LD) conditions. We assayed the duration of three pre-adult stages in the faster developing (FD) and control (BD) populations under a variety of light regimes that are known to modulate circadian clocks and pre-adult development time of Drosophila to examine the role of circadian clocks in the timing of pre-adult developmental stages. Results: We find that the duration of pre-adult stages was shorter under constant light (LL) and short period light (L)/dark (D) cycles (L:D = 10:10 h; T20) compared to the standard 24 h day (L:D = 12:12 h; T24), long LD cycles (L: D = 14:14 h; T28) and constant darkness (DD). The difference in the duration of pre-adult stages between the FD and BD populations was significantly smaller under the three LD cycles and LL compared to DD, possibly due to the fact that clocks of both FD and BD flies are driven at the same pace in the three LD regimes owing to circadian entrainment, or are rendered dysfunctional under LL. Conclusions: These results suggest that interaction between light regimes and circadian clocks regulate the duration of pre-adult developmental stages in fruit flies D. melanogaster. Open Access

2014-01-01T00:00:00Z