Raju Radder

raju

Position: Post-Doc
Year: 2004 - 2008

20/7/1973 - 31/5/2008

Passed away suddenly at his home in India

Watch youtube tribute here


General Research Interests

Reproduction is an important event in the life history of every organism since biological fitness or the ability of an organism to transfer its genes to the next generation is considered in terms of life time reproductive success. Hence, I am interested in understanding the ways in which natural selection has fashioned reproductive strategies to ultimately enhance reproductive fitness. I would like to integrate various aspects of developmental biology, endocrinology and ecology, to provide a more comprehensive understanding of reproductive strategies and their evolution in reptiles. My most noteworthy contributions to date include providing experimental evidence to show that stress experienced by a reproductive female reptile can directly cause prolonged uterine retention of eggs, a step in the transition between oviparity and viviparity. This idea was proposed several years ago by Shine and Guillette, on purely theoretical grounds, but my work provides the first empirical verification of such a phenomenon. My recent studies also have provided the first evidence on the mechanism(s) by which lizards can achieve ‘embryonic diapause’ during this prolonged egg retention: that is, by selecting lower body temperatures. I have also worked on testing among competing hypotheses (optimality versus constraint) for the evolution of egg and offspring size, role of socio-sexual factors in reproduction, ontogeny of sexual size dimorphism, contextual use of pushup displays in tropical multi-clutched lizards (Psammophilus dorsalis, below). I am also interested in studying the behaviour of lizards and anuran tadpoles.

rock lizard rock lizard

male rock lizard (Psammophilus dorsalis)

female Psammophilus dorsalis


Research Techniques: histology, enzyme histochemistry, ELISA, RIA, captive breeding of lizards, biostatistics, statistical modeling.

Research

Of all inborn differences that distinguish individual humans, as well as other animals, sex exerts the most far-reaching effects, and what determines it, has been debated throughout history (not surprisingly for over 3000 years!). Especially, reptiles display a remarkable diversity of sex-determining mechanisms. In some species, the sex of an individual is determined at conception, by genetic factors that may or may not involve overtly differentiated heteromorphic sex chromosomes. In other (and sometimes closely-related) species, sex is determined instead at a later stage in development, as a response to the incubation environment that the egg experiences. By far the most important environmental factor in this respect appears to be the thermal regime encountered during incubation. But the fundamental question “why is the sex of some reptiles determined by their genetic constitution whereas in other species the animal’s sex is determined by the environment (especially, incubation temperature)?” remains unanswered. Multiple phylogenetic transitions between genetic sex determination (GSD) and environmental sex determination (ESD) suggest that these alternative modes of sex determination possess adaptive significance. However, the selective forces favouring one versus the other remain obscure, despite sustained research in this field by many workers. The recent discovery of BOTH sex-determining systems simultaneously within a single population of alpine lizards by Professor Rick Shine and co-workers provides a unique opportunity to test among competing hypotheses for the evolution of sex-determining systems. Thus, I am currently at Rick Shine’s lab and involved in an integrated study, in both the field and laboratory, to clarify the mechanisms and the selective forces involved in the evolution of sex-determination in reptiles.

chameleon

Cape Dwarf Chameleon (Bradypodion pumilum), Stellenbosch, South Africa

Education

1994 
BScKarnatak University, Dharwad, India
1996
MScKarnatak University, Dharwad, India   (Gold medal)
2001
PhDKarnatak University, Dharwad, India -Studies on reproduction in the lizard,Calotes versicolor(Daud.) with reference to sex steroid cycles, factors controlling gonadal recrudescence and fecundity.

garden lizard

garden lizard (Calotes versicolor)

Publications

Publications in Refereed Journals

Some papers are available as pdf files. To read these you will need Adobe Acrobat Reader.
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1.
Radder, R. S., B. A. Shanbhag, and S. K. Saidapur. 1998. Prolonged oviductal egg retention arrests embryonic growth at stage 34 in captiveCalotes versicolorHerpetological Review 29:217-218.
2.
Shanbhag, B. A.,R. S. Radder, and S. K. Saidapur. 2000. GnRH but not the warm temperature induces recrudescence of quiescent testes in the tropical lizard,Calotes versicolor(Daud.).General and Comparative Endocrinology 119:232-236.
3.
Shanbhag, B. A.,R. S. Radder, and S. K. Saidapur. 2000. Maternal size determines clutch mass while breeding timing influences clutch and egg sizes in a tropical lizard,Calotes versicolor(Agamidae).Copeia 2000:1062-1067.
4.
Radder, R. S., B. A. Shanbhag, and S. K. Saidapur. 2001. Ontogeny of sexual size dimorphism in the tropical garden lizard,Calotes versicolor(Daud.).Journal of Herpetology  35:156-160.
5.
Shanbhag, B. A.,R. S. Radder, and S. K. Saidapur. 2001. Plasma progesterone levels and luteal activity during gestation and prolonged oviductal egg retention inCalotes versicolor.General and Comparative Endocrinology 123:73-79.
6.
Radder, R. S., B. A. Shanbhag, and S. K. Saidapur. 2001. Patterns of plasma sex steroid levels during reproductive cycles in male and female tropical lizards,Calotes versicolor.General and Comparative Endocrinology 124:285-292.
7.
Radder, R. S., B. A. Shanbhag, and S. K. Saidapur. 2002. Influence of incubation temperature and substrates on eggs and embryos of the garden lizard, Calotes versicolor(Daud.) Amphibia-Reptilia 23:71-82.
8.
Radder, R. S., B. A. Shanbhag, and S. K. Saidapur. 2002. Pattern of yolk internalization by hatchlings is related to breeding timing in a lizard,Calotes versicolor.Current Science 82(12):1484-1486.
9.
Shanbhag, B. A.,R. S. Radder, and S. K. Saidapur. 2002. Members of the opposite sex mutually regulate gonadal recrudescence in a tropical lizard,Calotes versicolor.Journal of Biosciences 27:529-537.
10.
Shanbhag, B. A., S. K. Saidapur, andR. S. Radder. 2003. Lowering body temperature inCalotes versicolor: a mechanism for embryonic diapause during prolonged egg retention.Naturwissenschaften 90:33-35.
11. Radder, R. S., and B. A. Shanbhag. 2003. Interrelationships among reproductivetraits of the female lizard,Sitana ponticeriana.Current Science 85(1):89-91.
12. Shanbhag, B. A.,R. S. Radder,N. P. Gramapurohit, K. V. Dheeraj, A. Veena, B. N. Pandav, and S. K. Saidapur. 2003. Demography of the fan throated lizard,Sitana ponticeriana(Cuvier) in Dharwad district of Karnataka State, India.Current Science 85(9):1363-1366.
13. Radder, R. S., and B. A. Shanbhag. 2004. Factors influencing offspring traits in the tropical lizard,Calotes versicolor.Journal of Biosciences 29:105-110.
14. Radder, R. S., B. A. Shanbhag, and S. K. Saidapur. 2004. Yolk partitioningstrategy in the lizardCalotes versicolorembryos: maximize body size or save energy for later use?Journal of Experimental Zoology 301:783-785.
15. Radder, R. S., S. K. Saidapur, and B. A. Shanbhag. 2005. Population density, microhabitat use and activity pattern of the Indian rock lizard,Psammophilus dorsalis.Current Science 89:560-565.
16.
Radder, R. S., S. K. Saidapur, and B. A. Shanbhag. 2006. Big boys on top: effects of body size, sex and reproductive state on perching behaviour in the tropical rock dragon,Psammophilus dorsalis.Animal Biology 56:311-321.
17.
Radder, R. S., S. K. Saidapur, R. Shine, and B. A. Shanbhag. 2006. Language of lizards: interpreting visual displays in the Indian rock lizard,Psammophillus dorsalis.Journal of Ethology 24:275-283.
18.
Radder, R. S., and R. Shine.  2006.  Thermally-induced torpor in fullterm lizard embryos synchronises hatching with ambient conditions.Biology Letters 2:415-416.
19.
Radder, R. S.2006.  An overview of geographic plasticity in life history traits of an agamid lizard,Calotes versicolor. (review)Current Science 91:1354-1363.
20.
Deeraj, K. V., B. A. Shanbhag,R. S. Radder,and S. K. Saidapur. 2007. Ontogenyand repeatability of performance ability in the tadpoles and metamorphs of the frog,Tomopterena breviceps. Under Review.
21.
Radder, R. S., D. Warner, J. Cuervo, and R. Shine.  2007.  The functional significance of residual yolk in hatchling lizards(Amphibolurus muricatus, Agamidae).Functional Ecology 21:302-309.
22.
Radder, R., and R. Shine.  2007.  Germinal bed condition in a polyautochronic single-clutched lizard,Bassiana duperreyi(Scincidae). Amphibia-Reptilia 28:159-162.
23.
Radder, R. S., S. Ali, and R. Shine.  2007.  Offspring sex is not related to maternal allocation of yolk steroids in the lizard,Bassiana duperreyi(Scincidae).Physiological and Biochemical Zoology 80:220-227.
24.
Radder, R. S., and R. Shine.  2007.  Sex-based hatching asynchrony in an oviparous lizard (Bassiana duperreyi, Scincidae).Austral Ecology 32:502-508.
25.
Shine, R., D. Warner, andR. S. Radder.2007. Windows of sexual liability during embryonic development in two lizard species with environmental sex determination.Ecology 88:1781-1788.
26.
Radder, R. S., and R. Shine. 2007. Are the phenotypic traits of hatchling lizards affected by maternal allocation of steroid hormones to the egg? General and Comparative Endocrinology 154:111-119.
27.
Radder, R. S., and R. Shine. 2007. Why do female lizards lay their eggs in communal nests?Journal of Animal Ecology 76:881-887.
28.
Radder, R. S.2007. Maternally-derived egg yolk steroids and sex determination: review of a paradox in reptiles.Journal of Biosciences 32:1213-1220.
29.
Radder, R. S., D. Warner, and R. Shine. 2007. Compensating for a bad start: catch-up growth in juvenile lizards (Amphibolurus muricatus, Agamidae).Journal of Experimental Zoology 307A:500-508.
30.
Radder, R. S., L. Pizzatto, and R. Shine. 2008. Morphological correlates of life history variation: is lizard clutch size related to the number of germinal beds in the ovary?Biological Journal of the Linnean Society 94:81-88.
31. Radder, R., M. Elphick, D. Warner, D. Pike, and R. Shine. 2008. Reproductive modes in lizards: measuring the fitness consequences of prolonged uterine retention of eggs. Functional Ecology 22:332-339.
32. Warner, D. A.,R. S. Radder, and R. Shine. 2008. Corticosterone exposure during development affects offspring growth and sex ratios in opposing directions in two lizard species with environmental sex determination. Physiological and Biochemical Zoology:in press subject to final revision.
33. Radder, R. S., A. E. Quinn, A. Georges, S. D. Sarre, and R. Shine. 2008. Genetic evidence for co-occurrence of chromosomal and thermal sex-determining systems in a lizard.Biology Letters 4:176-178.

Book Reviews

1.
Radder, R. S.2006.  Book title: “Temperature-Dependent Sex Determination in Vertebrates” (2004) edited by Nicole Valenzuela and Valentine Lance.Current Science 90:1008-1009.
2.
Radder, R. S.2006.  Book title: “Incubation of Reptile Eggs” (2005) by Gunther Kohler.Applied Herpetology 3:173-178.
3.
Radder, R. S.2006.  Book title: “Elsevier’s Dictionary of Herpetology and Related Terminology”.Current Science 91:1103.
4.
Radder, R. S.2007. Book title: “Toxicology of Reptiles” (2006) edited by Susan C. Gardner and Eva Oberdörster.Current Science 93:254-255.

Popular Science Articles in Refereed Journals

1.
Radder, R. S.2006.  On teaching the theory of evolution.Resonance 11(4):100-105.
2.
Radder, R. S.2006.  Importance of biology (Correspondence).Current Science 90:1587-1588.

Presentation

1.
Radder, R. S.2006.  Reading the book of life.http://www.nfsci.org/(presentation)

Awards

2003 Indian National Science Academy (INSA). Young Scientist Award Medal for outstanding contribution in Animal Science Research.
2002 Indian Science Congress Association (ISCA). Young Scientist Award in the section "Zoology, Entomology and Fisheries".
2001 First prize for best oral paper presentation at the "National Symposium on Trends in Environmental and Evolutionary Biology" held at Karnatak University, Dharwad.
1996 Dr. V. B. Nadkarni "Gold Medal" for ranking first in M. Sc.
1996 Dr. M. Appaswami Rao commemoration cash prize for securing highest marks in "Comparative Endocrinology and Reproductive Biology" paper in M. Sc. Final year examination.
1996 First prize for best seminar presentation from Natural History Association (NHA), Department of Zoology, Karnatak University, Dharwad.
1995 Cash prize and a medal for securing highest marks in M. Sc., Nijalingappa Hostel, Karnatak University, Dharwad.

Fellowships and Scholarships

1996-1998 University Research Studentship, Karnatak University, Dharwad.
1998-2000 Junior Research Fellowship, Department of Science and Technology, India (DST).
2000-2002 Senior Research Fellowship, Department of Science and Technology, India (DST).
2002 Senior Research Fellowship (SRF - Extended), Council of Scientific and Industrial Research, India (CSIR).
2002-2004 Research Associateship, Council of Scientific and Industrial Research, India (CSIR).
2004-2007 Post-Doctoral Fellowship, Australian Research Council (ARC).
2005
University of Sydney, Australia Post-Doctoral Fellowship start up grant.
2006
Environmental Futures Network, Australia. Early career research grant.
2008-09 Bridging Fellowship, University of Sydney

rock lizard

Psammophilus dorsalis

Symposia and Conferences

1996 National Symposium on Vertebrate Reproduction, Department of Zoology, Karnatak University, Dharwad, India.
1997 One day workshop on Research Methodology sponsored by Academic Staff College, Karnatak University, Dharwad, India.
1998 Workshop on Vertebrate Reproduction sponsored by Department of Science and Technology, held in Department of Zoology, Karnataka University, Dharwad, India.
2000 Refresher course in Animal Sciences, sponsored by Indian Academy of Sciences, Bangalore, India.
2001 National Symposium on Trends in Environmental and Evolutionary Biology, Karnatak University, Dharwad, India.
2002 89th Annual Session of Indian Science Congress, Lucknow University, Lucknow, India.
2002 National conference on Frontiers in Biology, Dharwad, India.
2002 Refresher course in Vertebrate Reproduction, Indian Academy of  Sciences, Bangalore, India.
2003 Fourteenth Mid-Year Meeting of the Indian Academy of Sciences, Bangalore, India.
2003 Humboldt Kollegue, sponsored by Alexander van Humboldt Foundation, Germany. Held at MAHE Manipal, India.
2004
First Australian Sex Summit, Flowerdale (Melbourne), Australia. July 14-16.
2005
5th World Congress of Herpetology, Stellenbosch, South Africa. June 19-24.
2006
Joint meeting of The American Society of Ichthyologists and Herpetologists. New Orleans (Louisiana, USA). July 12-18.
2006
“International Workshop on Evolutionary Ecology: Sex Allocation in Reptiles” Wollongong University, NSW, Australia. April 1-2.
2006
Australian Society of Herpetologists Annual Meeting. Healesville, Victoria, Australia. April 18-21.
2007 Evolution conference, Christchurch, New Zealand. June 16-20.

cape skink

Cape skink (Mabuya capensis), Capetown, South Africa

Membership of Professional Societies

Life member of the Society for the Study of Amphibians and Reptiles (SSAR), USA
Life member of American Society of Ichthyologists and Herpetologists (ASIH), USA
Life member of Herpetologists League (HL), USA
Life member of Societas Europaea Herpetologica (a pan-European herpetological network)
Regular member the Australian Society of Herpetologists
NRI member of the Novel Foundation for Science, India

raj