P. D. Tewary's research while affiliated with Banaras Hindu University and other places

... Spotted munia (Lonchura punctulata) responds to unnaturally short photoperiods (ranging from 0.25-6 h) but the customary long and short days (ranging from 8-24 h) fail to stimulate gonadal growth; long days rather retard or inhibit it [53], red-billed quelea (Quelea quelea) are photoperiodic exhibiting brief refractory period that terminates spontaneously irrespective of photoperiodic condition [54]. Our study on the photoperiodic responses of tree sparrow stands in contrast to those mentioned above but resembles to those of some subtropical birds, e.g., red-headed bunting (Emberiza bruniceps) [55,56], black-headed bunting (Emberiza melanocephala) [57], rosefinch (Carpodacus erythrinus) [24,58], yellow-throated sparrow (Gymnorhis xanthocollis) [59] and house sparrow (Passer domesticus) [39]. Though the timing of peak gonadal growth was similar under both the stimulatory light regimes in the tree sparrow, the testicular growth and regression were faster in the birds under 14L/10D as compared to 12L/12D (Figure 2A). ...

Reference:

Photoperiod as a proximate factor in control of seasonality in the subtropical male Tree Sparrow, Passer montanus

... Long day lengths ($11.5 h per day) stimulate fattening and gain in body mass plus gonadotrophin release and gonadal development, [27,28] but under short day lengths (#11.5 h per day) birds remain unstimulated without significant increase in body mass and no testicular growth. A strongly selfsustained circadian system [5,10] mediates the blackheaded bunting's responses to light, and the daily period of maximum photoinducibility (fi) begins early in night, e.g., between zt 11 and 12 in birds entrained to 6h:18h LD. [15,16,19] Three experiments were conducted on a batch of adult male birds that were caught in March 1999 (Experiment I) or March 2000 (Experiments II and III) from the over-wintering flock at 258N and maintained for about 10 (Experiment I) or 12 wk (Experiment II) on short day lengths (8h:16h, 8:16 LD; L ¼ 450 lux; D ¼ 0 lux), ensuring their photosensitivity until the beginning of the experiments. Thus, all experiments were performed on short-day birds in which testes remain small and unstimulated ðrange of testis volume ¼ 0:21 -0:33 mm 3 Þ: We used an experimental paradigm of skeleton photoperiods with 2 light ðL ¼ 450 luxÞ periods of the same or different durations separated by a dark (D ¼ 0 lux; except in the Experiment I in which D ¼, 1 lux) period. ...

Reference:

The photoperiodic entrainment and induction of the circadian clock regulating seasonal responses in the migratory blackheaded bunting (Emberiza melanocephala)

... In the cycle of 24 h (3L/21D), the light period always falls in the nonphotoinducible phase, without any phase advance or delay of the cycle, precluding the possibility of any response. Thus, the results of the present experiment are in agreement with the results of resonance and night interruption experiments performed on yellow-throated sparrows (Tewary et al. 1984;Dixit, 1987). Although these results demonstrate the involvement of endogenous circadian rhythm(s) during photoperiodic time measurement in this species and are consistent with the Biinning hypothesis, that is not the only hypothesis with which they are consistent. ...

Reference:

Involvement of A Circadian Rhythm in the Photoperiodic Ovarian Response of the Yellow-Throated Sparrow, Gymnorhis Xanthocollis

... Studies up to now have dealt primarily with the demonstration of an endogenous circadian rhythm which appears to be involved in photoperiodic time measurement Kumar 1981b, c, 1982;Tewary et al., 1982b). Also in common Indian rosefinches (Carpodacus erythrinus), a subtropical migratory species, we have found that an endogenous circadian rhythm is involved in the initiation of testicular growth and in the maintenance of size of the testes (Tewary and Kumar, 1981c;Kumar and Tewary, 1982). The present investigation examines the induction of gonadal growth in male rosefinches by means of experimental photoregimes 0378-4320/83/0000---0000/$03.00 © 1983 Elsevier Scientific Publishing Company that include interruption of the scotophase by light at intervals designed to reveal the photosensitive phase of the response mechanism. ...

Reference:

Circadian function in the photoperiodic induction of testicular growth in the common indian rosefinch, Carpodacus erythrinus

... The timing of light pulse during a critical window of inducibility (12-14 h after light onset) results in reproductive development. Tewary, 1990;Saunders, 1979;Simpson & Follett, 1982;Tewary & Kumar, 1982b;Tewary & Prasad, 1983). The precise nature of the molecular substrates that provide interval timing for the external coincidence is described in detail below. ...

Reference:

Photoperiodic regulation of avian physiology: From external coincidence to seasonal reproduction

... In the past about 70 years, an extensive body of information on annual gonadal cycles and their control mechanisms is available from various studies conducted on the Indian birds including migratory as well as nonmigratory forms of different orders and families, e.g. Indian owls, Anthenabrama, Bubo bubo, Ketupazeylonensis and Tyto alba (Thapliyal, 1954); doves, Streptopelia tranquebarica, Streptopelia senegalensis (Singh, 1958); crows, Corvus macrorhyncos macrorhyncos, Corvus splendens splendens (Prasad, 1959); pigeons, Columba livia (Dominic, 1960); Indian lalmunia, Estrilda amandava (Tewary & Thapliyal, 1962); mynas, blackheaded mynah, Temenuchus Pagodarum, bank mynah, Acridotheres ginginianus, common Indian mynah, Acridotheres tristis, pied mynah, Sturnopastor contra (Tewary, 1967); redheaded bunting, Emberiza bruniceps (Prasad, 1980); blackheaded bunting, Emberiza melanocephala, rosefinch, Carpodacus erythrinus (Kumar, 1981); weaver birds, Ploceus philippinus ; yellowthroated sparrow, Gymnorhis xanthocollis, (Tewary & Dixit, 1986); house sparrow, Passer domesticus (Trivedi, 2005); tree spar row, Passer montanus (Dixit & Singh, 2011) yellowbreasted bunting, Emberiza aureola (Dixit & Sougrakpam, 2013). A detailed analysis of the above studies clearly reveal that, in contrast to temperate avian species which breed during narrow window of the year in summer, the Indian birds have more flexible breeding programs and exhibit a spectrum of reproductive strategies with the breeding season scattered all over the year in spring, summer, autumn, and winter months. ...

Reference:

Control of annual gonadal cycles in Indian songbirds

... The internal coincidence model, on the other hand, predicts that an external photophase brings two or more circadian oscillator, present in the photoperiodic clock and coupled separately to dawn and dusk, into a particular phase relationship with one another resulting in a photoperiodic response. Thus, while the external coincidence model embraces the dual function of light as entrainer as well as inducer, light serves only as an entertainer agent and does not directly induce a photoperiodic response in the internal coincidence model [18]. One of the powerful experimental paradigms that can be used to test for the involvement of the circadian system in photoperiodic time measurement is the use of intermittent light-dark cycles experiment. ...

Reference:

Photoperiod and circadian rhythmicity in testicular response of the tree sparrow

... The timing of light pulse during a critical window of inducibility (12-14 h after light onset) results in reproductive development. Tewary, 1990;Saunders, 1979;Simpson & Follett, 1982;Tewary & Kumar, 1982b;Tewary & Prasad, 1983). The precise nature of the molecular substrates that provide interval timing for the external coincidence is described in detail below. ...

Reference:

Photoperiodic regulation of avian physiology: From external coincidence to seasonal reproduction

... Spotted munia (Lonchura punctulata) responds to unnaturally short photoperiods (ranging from 0.25-6 h) but the customary long and short days (ranging from 8-24 h) fail to stimulate gonadal growth; long days rather retard or inhibit it [53], red-billed quelea (Quelea quelea) are photoperiodic exhibiting brief refractory period that terminates spontaneously irrespective of photoperiodic condition [54]. Our study on the photoperiodic responses of tree sparrow stands in contrast to those mentioned above but resembles to those of some subtropical birds, e.g., red-headed bunting (Emberiza bruniceps) [55,56], black-headed bunting (Emberiza melanocephala) [57], rosefinch (Carpodacus erythrinus) [24,58], yellow-throated sparrow (Gymnorhis xanthocollis) [59] and house sparrow (Passer domesticus) [39]. Though the timing of peak gonadal growth was similar under both the stimulatory light regimes in the tree sparrow, the testicular growth and regression were faster in the birds under 14L/10D as compared to 12L/12D (Figure 2A). ...

Reference:

Photoperiod as a proximate factor in control of seasonality in the subtropical male Tree Sparrow, Passer montanus

... Increasing photoperiod is an important cue for onset of breeding in seasonal breeders, but also causes gonadal regression through photorefractoriness at later dates (Williams et al., 1987; Beebe et al., 2005). Other than photoperiod, endogenous circannual components (Mishra & Tewary, 1999; Dawson et al., 2001) and availability of food (Perfito et al., 2004; Caro et al., 2006) also regulate breeding and associated events. Certain birds are known to acquire calcium shortly before and during egg laying by eating extraneous calcium and do not store calcium for egg production (Dhondt & Hochachka, 2001). ...

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Distribution, habit and reproductive activity of bank myna, Acridotherus giginianus (Latham) in relation to natural photoperiod.