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Freek Vonk

F.J. (Freek) Vonk, Research fellow - Character Evolution


Email: research.vonk@naturalis.nl
Phone: -
Room number: -
“My curiousity about nature is never satisfied.”

Ever since I was a child, I was fascinated by nature and wild animals. From the moment I discovered the life of snakes, my love for biology increased every day. As a 15 year old boy, the diversity of snake species and their wide range of adaptations caught my attention. That's when I decided that I wanted to study biology in order to learn more about these animals.

After my study in biology and my promotion at Leiden University, I started working at Naturalis Biodiversity Center. My curiousity is still not satisfied. There are so many questions. Every day I am very happy to work on my scientific research. But at the same time I try to convey my knowledge and passion about nature to the general public. I think it's important to reach out to people and touch their hearts in order to get the message across that we need to care about the wonderful life on earth.

King cobra (Ophiophagus hannah). 


2014-2018 Postdoc Naturalis Biodiversity Center
2012-2014 Postdoc Molecular Ecology and Evolution Group, Bangor University (Wales, UK)
September 6, 2012 PhD. "Snake evolution and the application of snake venom." Leiden University
May 24, 2008 MSc. Biology Leiden University

International activities

September 2014 – September 2018 Postdoctoral researcher at the Naturalis Biodiversity Center studying the genomes of the Malayan pit viper and the king cobra.
September 2012 – March 2014 Postdoctoral researcher at the the Molecular Ecology and Evolution Group at Bangor University in Wales (UK), sequencing and studying the genomes and transcriptomes of the king cobra (Ophiophagus hannah).
January – April 2010 Expedition to Australia to collect venom from snakes throughout Australia and visit laboratories at the Universities of Brisbane and Sydney, funded by Technology Foundation STW, the Leiden University Fund and the Gratama stichting.
January – February 2009 Research trip to Australia: to the University of South Australia, Australian Venom Research Unit (University of Melbourne) and the Venom Supplies venom laboratories to lecture and collect venom samples from Australian snakes for venom studies.
March 2008 Invited to lecture at the University of Tel Aviv and the University of Haifa. 
January to April 2006 Internship at the University of Melbourne, the Australian Venom Research Unit, constructing cDNA libraries of the venom glands of several species of venomous snakes.
December 2005 Invited to lecture at the University of South Australia on embryonic gene-expression studies in snakes.

Additional academic activities

Editorial Board 

  • Journal of Venom Research (2011 - present) 
  • Toxins (2013 – present)


  • Eureka Prize, 2012
  • Profiled by Science magazine, 6 december 2013, 1164-1165


  • Member of the International Society for Toxinology (2005 - present)
  • Advisory Council venomous snakes, The Herpetofauna Foundation (2010 - present)

Conference presentations and invited academic seminars 

  • 2013 Scientific Advisory Board, Naturalis Biodiversity Center
  • 2012 German Zoological Society, Leipzig (Germany)
  • 2011 Indian conference for Toxinology (India) 
  • 2011 Netherlands Annual Ecology Meeting honorary lecture (Lunteren)
  • 2010 University of Antwerp (Belgium)
  • 2010 Next Generation Sequencing in Biodiversity Studies (Naturalis)
  • 2009 The sixth World Congress of Herpetology (Manaus, Brazil)
  • 2009 Kennis op Zondag (Nemo Theatre, Netherlands)
  • 2009 Sansom Institute Visiting Research Scholar Seminar (Australia) 
  • 2008 Discovery08 (Nemo Theatre, Netherlands)
  • 2008 The Cleveringe Lecture (Netherlands)
  • 2008 Israel Institute of Technology (Israel)
  • 2008 In The Spotlight lecture (Leiden University, Netherlands)
  • 2008 This Week’s Discoveries (Leiden University, Netherlands)
  • 2008 University of Tel Aviv Hebrew (Israel)
  • 2008 University of Jerusalem (Israel)
  • 2008 Leiden University (Netherlands)
  • 2007 The Clevering Lecture (Netherlands)
  • 2006 12th Benelux Congress of Zoology (Netherlands, invited) 
  • 2006 University of Utrecht (Netherlands)
  • 2005 University of South-Australia (Australia)
  • 2005 This Week’s Discoveries (Leiden University, Netherlands)

Scholarships, grants and prizes

  PI Amount  Year
Innovational Research Incentives Scheme VENI €250.000 2014
Rubicon grant €135.000 2012
Eureka Prize (*) €12.500 2012
NWO Toptalent grant €180.000 2008

(*) The Royal Netherlands Academy of Arts and Sciences (KNAW) and the Netherlands Organisation for Scientific Research (NWO) award the Eureka Prize once a year to a scientist who has done an outstanding job of communicating scientific research to the general public.


Research interest

My work is focused on the origin and evolution of reptile venom, venom glands and fangs. By performing gene-expression studies in snake embryos I built a solid hypothesis for the evolution of snake venom-conducting fangs (Nature, 2008), and identified a major evolutionary transition underlying the massive radiation of advanced snakes. Based on the data obtained I put forward a new model for the evolution of snake fangs: a posterior sub-region of the tooth-forming epithelium became developmentally uncoupled from the remaining dentition, which allowed the posterior teeth to evolve independently and in close association with the venom gland, becoming highly modified in different lineages.

More recently, by sequencing the genomes and the transcriptomes of the venom gland, accessory gland and a multi-tissue archive of two species of snake (king cobra and the Burmese python), followed by extensive evolutionary analysis of the toxin sequences, we have been able to confirm for the first time a previously proposed but poorly documented hypothesis about the origin and evolution of snake venom genes by (i) gene duplication and (ii) gene hijacking of ‘physiologically normal’ non-toxic proteins expressed in non-venom gland tissues such as stomach, spleen, liver, blood, testes, and ovaries (PNAS 2013 and PNAS 2013).

I have also obtained evidence for the co-option of core genetic regulatory components of the venom-system from a pancreatic origin. This work also led to new information about the enigmatic ‘accessory gland’, a small gland with unknown function associated with the venom gland in the two main groups of venomous snakes (Elapidae and Viperidae).


snake venom, snake, evolution, gene sequencing, venom glands

Current research topics

Venom of snakes





Under construction.

Available student projects

Public outreach


Freeks Wilde Wereld, Freek in het Wild, Freek op Safari (Zapp/VPRO)

Freek Vonk in Australië (BNN/VARA)

De Wereld Draait Door (VARA)


Giel! (VARA)


National Geographic Magazine, TrosKompas


Top 5 publications

  1. Vonk FJ et al. The king cobra genome reveals dynamic gene evolution and adaptation in the snake venom-system. PNAS 110, 20651-20656 (2013)
  2. Vonk FJ et al. Evolutionary origin and development of snake fangs. Nature 454, 630-633 (2008) 
  3. Vonk FJ & Richardson MK. Serpent clocks tick faster. Nature 454, 282-283 (2008)
  4. Castoe TA et al, The Burmese python genome reveals the molecular basis for extreme adaptation in snakes. PNAS 110, 20645-20650 (2013)
  5. Fry BG et al. Early evolution of the venom-system in lizards and snakes. Nature 439, 584-588 (2006)

International (refereed) journals

Vonk FJ , Casewell NR, Henkel CV, Heimberg A, Jansen HJ, McCleary RJR, Kerkkamp H, Vos R, Guerreiro I, Calvete JJ, Wuster W, Woods AE, Logan J, Harrison RA, Castoe TA, de Koning APJ, Pollock DD, Yandell M, Calderon D, Renjifo C, Currier RB, Salgado D, Pla D, Sanz L, Hyder AS, Ribeiro JMC, Arntzen JW, van den Thillart GE, Boetzer M, Pirovano W, Dirks R, Spaink HP, Duboule D, McGlinn E, Kini RM & Richardson MK. The king cobra genome reveals dynamic gene evolution and adaptation in the snake venom-system. PNAS 110, 20651-20656 (2013).

Castoe TA, de Koning APJ, Hall KT, Card DC, Schield DR, Fujita MK, Ruggiero RP, Degner JF, Daza JM, Gu W, Reyes-Velasco J, Shaney KJ, Castoe JM, Fox SE, Poole AW, Polanco D, Dobry J, Vandewege MW, Li Q, Schott RK, Kapusta AK, Minx P, Feschotte C, Uetz P, Ray DA, Hoffmann FG, Bogden R, Smith EN, Chang BS, Vonk FJ, Casewell NR, Henkel CV, Richardson MK, Mackessy SP, Bronikowsi AM, Yandell M, Warren WC, Secor SM & Pollock DD. The Burmese python genome reveals the molecular basis for extreme adaptation in snakes. PNAS 110, 20645-20650 (2013).

Casewell NR, Wüster W, Vonk FJ, Harrison RA & Fry BG. Complex cocktails: the evolutionary novelty of venoms. Trends Ecol Evol. 28, 219-229 (2013).

Otvos RA, Heus F, Vonk FJ, Halff J, Bruyneel B, Paliukhovich I, Smit AB, Niessen WM & Kool J. Analytical workflow for rapid screening and purification of bioactives from venom proteomes. Toxicon 76, 270-281 (2013).

Heus F, Vonk FJ, Otvos RA, Bruyneel B, Smit AB, Lingeman H, Richardson M, Niessen WM & Kool J. An efficient analytical platform for on-line microfluidic profiling of neuroactive snake venoms towards nicotinic receptor affinity. Toxicon 61, 112-124 (2013).

Vidal N, Marin J, Sassi J, Battistuzzi FU, Donnellan S, Fitch AJ, Fry BG, Vonk FJ, Rodriguez de la Vega RC, Couloux A, Hedges SB. Molecular evidence for an Asian origin of monitor lizards followed by Tertiary dispersals to Africa and Australasia. Biol Lett. 8, 853-855 (2012).

Vonk FJ, Jackson K, Doley R, Madaras F, Mirtschin PJ & N Vidal. Snake venom: from fieldwork to the clinic. BioEssays 33, 269-279 (2011).

Siang AS, Doley R, Vonk FJ, & RM Kini. Transcriptomic Analysis of the Venom Gland of the Red-headed Krait (Bungarus flaviceps) Using Expressed Sequence Tags. BMC Molecular Biology 11, 24 - 34 (2010).

Brittijn SA, Duivesteijn SJ, Belmamoune M, Bertens LFM, Bitter W, de Bruijn JD, Champagne D, Cuppen E, Flik G, Vandenbroucke-Grauls CM, Janssen RAJ, de Jong IM, de Kloet ER, Kros A, Meijer AH, Metz JR, van der Sar A, Schaaf MJM, Schulte-Merker S, Spaink HP, Tak PP, Verbeek FJ, Vervoordeldonk MJ, Vonk FJ, Witte F, Yuan H & MK Richardson. Zebrafish development and regeneration: new tools for biomedical research. Int. J. Dev. Biol. 53, 835-850 (2009).

Woltering JM, Vonk FJ, Muller H, Bardine N, Tuduce IL, de Bakker MAG, Knochel W, Sirbu IO, Durston AJ & MK Richardson. Axial patterning in snakes and caecilians: evidence for an alternative interpretation of the Hox code. Dev Biol. 332, 82-9 (2009).

Vonk FJ & Richardson MK. Serpent clocks tick faster. Nature 454, 282-283 (2008).

Vonk FJ, Admiraal JF, Jackson K, Reshef R, de Bakker MAG, Vanderschoot K, van den Berge I, van Atten M, Burgerhout E, Beck A, Mirtschin PJ, Kochva E, Witte F, Fry BG, Woods A & MK Richardson. Evolutionary origin and development of snake fangs. Nature 454, 630-633 (2008).

Bertola LD, Ott EB, Griepsma S, Vonk FJ & CP Bagowski. Developmental expression of the alpha-skeletal actin gene. BMC Evol Biol. 8, 166 (2008).

Vonk FJ & Wüster W. Roles of CITES in protecting new species. Science 313, 915-916. (2006).

Fry BG, Vidal N, Norman JA, Vonk FJ, Scheib H, Ramjan SF, Kuruppu S, Fung K, Hedges SB, Richardson MK, Hodgson WC, Ignjatovic V, Summerhayes V & E Kochva. Early evolution of the venom-system in lizards and snakes. Nature 439, 584-588 (2006).

Book chapters

Invited to contribute to the book “Evolution and venom of Toxicofera reptiles” edited by Dr. B.G. Fry that will be appear in print in 2015.

Invited to contribute to the handbook series Toxinology, edited by Professor P. Gopalakrishnakone that will be appear in print in 2015.