Prof. A. S. Dixit

Zoology Department

Designation: Professor


Ph.D. (1987): Banaras Hindu University, Varanasi.


  1. As faculty 
    • Vice- President: Indian Society for Chronobiology, 2019-2021.
    • Vice- President: Association of Avian Biologists in India, 2018-Contd.
    • Subjected Expert: Selection Committees for recruitment and promotion of faculty in some Indian Universities.
    • Reviewer for number of International Journals in Zoology/ Biology/ Behavior/ Chronobiology.
    • Editorial board member: Global Journal of Zoology; International Journal of Research Studies in Zoology; The NEHU journal.
    • Executive committee Member: Indian Society for Chronobiology, 2017-2021.
    • Vice- President: Indian Society for Chronobiology, 2013-2017.
    • Coordinator: 3rd DST-SERB School in Avian Biology, Shillong, 2015.
    • Member of the PG e pathsala team to develop e content for Zoology (Chronobiology) under UGC National Mission on Education through ICT (NME-ICT) Project.
    • Coordinator: DST-SERB School in Chronobiology, Shillong, 2012.
    • Member: National Coordination Committee, International Congress on Chronobiology, Dept. Zoology, Delhi University, 2012.
    • Member: DST-National Planning Committee for SERB School in Chronobiology, 2010-15.
    • Faculty: DST-SERC/SERB School in Chronobiology (2009-15).
    • Coordinator: DST-SERC School in Chronobiology, Shillong, 2009.
    • Member: Organizing Committee, 96th Indian Science Congress, NEHU, Shillong, 2009.
    • Reviewer for the development of NCERT Textbook in Biology (Class XII), 2006
  2. As student
    • Research Associate, CSIR-New Delhi, May 1988 to August 1990.
    • Sr. Research Fellow, CSIR-New Delhi, January 1986 to April 1988.
    • Sr. Research Fellow, UGC-SAP, March 1985 to December 1985.
    • Jr. Research Fellow, UGC-SAP, April 1983 to February 1985.
    • Certificate of Merit for best research paper and presentation, 71st ISCA, Ranchi, 1984.
    • B.H.U. Research Scholarship April 1981 to March 1983.

Teaching Experience:  ~29 years (Since August 1990)

Research Experience: ~ 39 years (Since March 1981)

Research focus

Cycles in biological systems are all pervasive in Nature. Birds like any other species express daily rhythms in activity/rest, hormone secretion and several other rhythmic characteristics. Most bird species also show long-term cycles in feeding behavior, body fattening (in migrants), reproduction, moult, or migration. Both daily and seasonal behaviors are under the strict control of the endogenous clock mechanisms, but the role of environment remains critical for optimal performance and ultimately the survival. Synchrony with the environment is achieved through interaction of clock component with external cues (e.g. photoperiod), and internal coordination among different rhythmic physiological correlates is achieved through neural and endocrine signaling. Thus, we are interested to learn about how birds achieve precision in timing their daily and seasonal activities in synchrony with the periodic environment. Our research effort mainly centers around the “Avian Circadian and Seasonal Systems: Study from Behavior to Molecules”. The working hypothesis has been that specialized cells localized in different tissues express genes involved in the clock circuitry, and different cell populations control the food intake, body fattening, reproductive axis, molt and migration, in a way that each event can be timed and spaced with each other to optimize an ecological adaptation.

Research Themes          

  • Clocks controlled daily and seasonal behaviors (e.g. migration and reproduction).
  • Neurobiology of seasonal behaviors. Neuronal changes in the brain (neurogenesis/synaptogenesis) in response to seasonality and hormone status. Hormonal modulation of brain functions.
  • Hypothalamic expressions and roles of GnIH and GnRH-I, TSHβ, Dio2 and Dio3 in photoperiodic regulation of avian seasonality.
  • Endocrinology of seasonal reproduction and related behaviors (with reference to hormones of HPG axis).
  • Physiology of reproduction and migration.
  • Metabolism: glucose uptake studies in response to daily and seasonal changes.
  • Endocrinology of free-living birds. Measurement of hormones and recording their behavioral changes.
  • Clock and metabolism using migratory birds as model systems.
  • Life style patterns and biological clock mediated functions in human.

Model systems

Non-migratory and migratory songbirds.

Techniques we use

  • Monitoring of activity rest rhythm and feeding behavior by using chronobiology software.
  • Anatomical modifications in the brain in relation to seasons and physiological status.
  • ELISA.
  • Non-invasive study of seasonality (feather regeneration and molt, body fattening, food intake, plumage and bill color scores etc.).
  • Metabolic activity through respirometer.
  • Immunohistochemistry.
  • PCR and Real time quantitative PCR.
  • Laparotomy and other approaches used for studying photoperiodism and seasonal reproduction.

Research Projects

  1. Role of proximate factors in timing the seasonal breeding in Passeriformes finches of North-East. DST, New Delhi (2008-2011).
  2. Role of kisspeptin and GnIH in regulation of seasonal breeding in the tree sparrow. DST, New Delhi (2013-2016).
  3. Anticipation in genes: Molecular, physiological and behavioral correlates of response of circa-       annual clocks to seasons in night-migratory songbirds: Investigation of physiological and metabolic adaptations in migrants”. DBT, New Delhi (2013-2018).
  4. Effect of climate change on breeding strategies of songbirds. DBT Twining, New Delhi.

Membership of Scientific Societies

  • Life and Executive Committee Member: Indian Society for Chronobiology.
  • Member: International Society for Chronobiology.
  • Member: DST National Planning Committee, SERB School in Chronobiology, Department of Science and Technology, New Delhi.
  • Member: International Ornithological Society.
  • Life member: Association of Avian Biologist in India.

Administrative Responsibilities                                                                                                         

  • Member: Academic Council, 01.01.2012 till date, North-Eastern Hill University, Shillong.
  • Member: Committee on National Institutional Ranking Framework, 21.10.2016 till date, North-Eastern Hill University, Shillong.
  • Member: Internal Quality Assurance Cell (IQAC), 29.05.2017 to 28.05.2019, North-Eastern Hill University, Shillong.
  • Member: Board of Research Studies, 1.8.2010 till date, North-Eastern Hill University, Shillong.
  • Member: School Board of life Sciences, 6.8.2008 to 5.8. 2010 and from 01.01.2012 till date North-Eastern Hill University, Shillong.
  • Member: Board of Study in Zoology, North-Eastern Hill University, Shillong.
  • Member: Board of Post Graduate Studies in Zoology, 28.5.2007 to 27.5.2010, North-Eastern Hill University, Shillong.
  • Member: Board of Under Graduate Studies in Pisciculture, 11.8. 2010 to 10.8. 2012, North-Eastern Hill University, Shillong.
  • Member: Vidyalaya Management Committee, 2010, Kendriya Vidyalaya, NEHU, Shillong.


  1. A. S. Dixit and S. Byrsat (2018). Photoperiodic control of GnRH-I expression in seasonal reproduction of the Eurasian tree sparrow. Photochem. & Photobiol. Sci. 17, 934-945. IF: 2.96.
  2. A. S. Dixit, I. Bamon and N. S. Singh (2018). Temperature modulates photoperiodic seasonal responses in the subtropical tree sparrow, Passer montanus. J. Comp. Physiol. A 204: 721-735. IF: 2.43
  3. A.S. Dixit, N.S. Singh and S. Byrsat (2017). Role of GnIH in photoperiodic regulation of seasonal reproduction in the Eurasian tree sparrow. J. exp. Biol. 220, 3742-3750. IF: 3.32, Citation 1
  4. A.S. Dixit, N.S. Singh and I. Bamon (2017). Photoperiodic time measurement and photoentrainment of circadian locomotor activity rhythm in subtropical tree sparrow. Photochem. & Photobiol. Sci. 16, 1146-1152. IF: 2.96. 
  5. A.S. Dixit, N. J. Gupta, V. Dwivedi and S.K. Bhardwaj (2017). Control of annual gonadal cycles in Indian songbirds. Biol. Rhythm Res., 1-21. IF: 0.69
  6. A.K. Trivedi, D. Singh, A.S. Dixit and V. Kumar (2017). Pineal gland, melatonin and timekeeping in non-mammalian vertebrates: Avian perspective. In: Biological Timekeeping: Clocks, Rhythms and Behaviour (ed. V. Kumar), Springer (India), DOI 10.1007/978-81-322-3688-7_25, pp. 521-541.
  7. A.S. Dixit, I. Bamon, S. Byrsat and R. Chetri (2017). Human circadian rhythms and their health implications. The NEHU J. Vol. XIII, No.1, Jan.-Jun. pp.97-118, Citation 1
  8. A.S. Dixit and N.S. Singh (2016). Seasonality in circadian locomotor activity and serum testosterone level in subtropical tree sparrow (Passer montanus). J. Photochem. Photobiol., B :biology 158, 61-68. IF: 2.96.
  9. N.S. Singh, I. Bamon and A.S. Dixit (2015). Structural variations and their adaptive significance in the bones of some migratory and resident birds. J. Basic and Appli. Zool.70, 33-40.
  10. A.S. Dixit, N.S. Singh and R. Sougrakpam (2014).  A comparative study on photoperiodic control of seasonal cycles in the females of   migratory yellow-breasted bunting and the resident tree sparrow. Photochem. Photobiol. Sci.13, 1568-1579.IF: 2.99, ISSN: 1474-9092. Citations 2
  11. A.S. Dixit and N.S. Singh (2014). Photoperiodic control of testicular growth, histomorphology and serum testosterone levels in the male tree sparrow: Involvement of circadian rhythm. Gen. Comp. Endocrinol.208, 5-11. IF: 2.6, ISSN: 1095-6840. Citations 2
  12. N.S. Singh and A.S. Dixit (2014). Morphology and ultrastructural studies of pineal organ of the tree sparrow (Passer montanus). Micron, 58: 9-14.IF: 1.9, ISSN: 0968-4328. Citations 2
  13. N. S. Singh and A. S. Dixit (2014). Participation of endogenous circadian rhythm in photoperiodic time measurement during ovarian responses of the subtropical tree sparrow, Passer montanus. Ind. J. Exp. Biol., 52(5) 1-7. IF: 1.2, ISSN: 0975-1009. Citations 2
  14. A. S. Dixit and R. Sougrakpam (2013). Photoperiodic regulation of seasonal reproduction, molt and body weight in the migratory male yellow-breasted bunting (Emberiza aureola). Anim. Repro. Sci. 141:98-108,(Netherlands). IF: 2.04, ISSN: 03784320. Citations 4
  15. A. S. Dixit and N. S. Singh (2013). Environmental control of seasonal reproduction in the wild and captive Eurasian Tree Sparrow (Passer montanus) with respect to variations in gonadal mass, histology and sex steroids. Can. J. Zool. (Canada). 91: 302-312. IF: 1.52, ISSN: 0008-4321. Citations 3
  16. A. S. Dixit and R. Sougrakpam (2012). Circadian rhythmicity in photoperiodic regulation of reproductive responses in the Yellow-breasted bunting. Biol. Rhythm. Res. 1-12 iFirst article, (UK). IF: 0.8, ISSN :1744-4179. Citations 4
  17. A. S. Dixit and N. S. Singh (2012). Seasonal variation in sensitivity of the photoperiodic response system in the subtropical tree sparrow (Passer montanus). J. Exp. Zool. 9999A: 1-12,(USA). IF: 3.36, ISSN: 1932-5231. Citations 4
  18. A. S. Dixit and N. S. Singh (2012). Photoperiod and circadian rhythmicity in testicular response of the tree sparrow. Biol. Rhythm Res. 1-8 iFirst article. DOI:10.1080/09291016.2012.692253, (UK). IF: 0.8, ISSN:1744-4179. Citation 1
  19. N. S. Singh and A. S. Dixit (2012). Involvement of endogenous circadian rhythm in photoperiodic ovarian response of subtropical tree sparrow, Passer montanus. IMRJ. 2(2): 66-72. ISSN: 2231-6302. Citation 1
  20. A. S. Dixit and N. S. Singh (2011). Photoperiod as a proximate factor in control of seasonality in the subtropical male tree sparrow, passer montanus. Front. Zool., 8:1-12, (USA). IF:4.46, ISSN: 1742-9994. Citations 27
  21. N. S. Singh, A. S. Dixit and R Sougrakpam (2011). A report on the presence of three avian lice (Insecta: Phthiraptera) in different regions of North-East India. JBNHS, 108 (1): 65-67.ISSN: 0006-6982.
  22. A. S. Dixit (2011). Photoperiod and Biological Rhythms in Regulation of Avian Reproduction. In: Perspectives in Animal Ecology and Reproduction (eds. V. K. Gupta, A. K. Verma and G. D. Singh), Daya Publication, Delhi, pp. 348-377.ISSN:978-81-7035-829-9.
  23. A. S. Dixit and M.K. Satapathy (2007). Biodiversity and its conservation strategies for sustainable development. In: Edu. Environment and Sustainable Development (ed. M.K. Satapathy), Shipra publications, Delhi, pp. 122-139.ISSN:81-7541-2190.
  24. A. S. Dixit (2004). Potentials of Biological Rhythms, Science Vision 4(3): 29-33. ISSN: 0975-6175.
  25. A. S. Dixit (2002). Environmental control of annual Reproductive and body weight cycles in female rosefinch and yellow-throated sparrow. J. Exp. Zool. India, 5(2): 207-216.ISSN: 0972-0030. Citations 2
  26. A. S. Dixit (2002). Importance of Living avian resources. In: Biological and Biotechnological Resources (eds. G. Tripathi and Y.C. Tripathi), Campus Books, New Delhi, pp. 303-312.ISSN: 8175412190.
  27. A. S. Dixit (2001). Photoperiodic Control of Reproduction in Birds. In: Current Topics in Environmental Sciences (eds. G. Tripathi and G.C. Pandey), ABD Publishers, Jaipur, pp 368-384.ISSN:81-8577-34-0.
  28. A. S. Dixit and P. D. Tewary (1989). Involvement of Circadian rhythm in photoperiodic ovarian response of the Yellow-throated Sparrow (Gynorhis xanthocollis), J. Exp. Biol., 143:411-418, (U.K.).IF:3.04, ISSN:0022-0949. Citations 2
  29. A. S. Dixit and P. D. Tewary (1989). Photoperiodic ovarian response in Yellow-throated Sparrow (Gymnorhis xanthocollis): involvement of circadian rhythm, Acta Physiol. Hung., 73(4): 455-460,  (Hungary), IF: 0.75, ISSN:0231-424X.
  30. A. S. Dixit (1989). Circadian periodicity and the termination of photo refractoriness in the female Yellow-throated Sparrow (Gymnorhis xanthocollis), Zool. Sci., 6:129-134, (Japan). IF: 0.82, ISSN:0289-0003.
  31. P.D. Tewary and A. S. Dixit (1988). Circadian periodicity in photoperiodic ovarian response of the Rosefinch (Carpodacus erythrinus), Zool. Jb. Physiol., 92:71-76, (Germany).
  32. P. D. Tewary and A. S. Dixit (1986). Photoperiodic regulation of reproduction in subtropical female Yellow-throated Sparrow (Gymnorhis xanthocollis), Condor, 88:70-73,(USA). IF:1.290, ISSN:1938-5129. Citations 22
  33. V. Kumar, P. D. Tewary and A. S. Dixit (1985). Participation of circadian component in the photoperiodic mechanism of Black-headed Bunting (Emberiza melanocephala), Anim. Reprod. Sci. 9:375-382, (Netherlands).IF: 2.036, ISSN: 0378-4320. Citations 7
  34. P. D. Tewary, A. S. Dixit and B. K. Tripathi  (1984). Circadian basis of photoperiodic ovarian response in the passerines. J. Ster. Biochem., 20: 1577, (USA).IF: 2.886, ISSN:0960-0760.
  35. P. D. Tewary, A. S. Dixit and V. Kumar (1984). Circadian rhythmicity and initiation of reproductive functions in female passerines, Physiol. Zool., 57 (5): 563-566, (USA), ISSN: 0031-935X, OCLC: 40114654. IF: 2.10, Citations 12
  36. P. D. Tewary and A. S. Dixit (1983). Photoperiodic control of ovarian cycle in Rosefinch, Carpodacus erythrinus . J. Exp. Zool., 228: 537-542, (USA).IF: 3.6, ISSN:1932-5231. Citations 20
  37. A. S. Dixit (1991). Mechanism involved in photoinduced ovarian growth in Yellow-throated Sparrow (Gymnorhis xanthocollis), Ind. J. Zool., 39: 86-89.
  38. A. S. Dixit, P. M. Tripathi and P. D. Tewary (1991). Control of bill coloration in the Yellow-throated Sparrow (Gymnorhis xanthocollis), Bull. Pure & Appl. Sci., 86: 104-107.ISSN:9070-0765.