Roel Wouters

    Roel Wouters is a young scientist from Leiden University with degree in biology and a passion for herpetology. He has experience in both the field and the lab, all around the world and he has been involved in multiple projects related to (venemous) snakes, ranging from ecology to biomolecular research. His current research is focused on the evolution and development of the infrared sensing pits in pitvipers, which will be main the topic of his talk.

    Evolution and Development of Infrared Sensing Pits in Pitvipers: From Fundamental Science to Conservation

    Roel M. Wouters1, Merijn de Bakker1, Bertie-Joan van Heuven2, Ingmar Werneburg3, Jory van Thiel1, Freek J. Vonk2, Marcelo Sanchez-Villagra4, Martin Rücklin2, Michael K. Richardson1*
    1 Animal Sciences & Health, Institute of Biology, Leiden University, 2300 RA Leiden, the Netherlands; WoutersRoel1@gmail.com (R.M.W.); M.A.G.de.Bakker@biology.leidenuniv.nl (M.A.G.B.); m.k.richardson@biology.leidenuniv.nl (M.K.R.).
    2 Naturalis Biodiversity Center, 2333 CR Leiden, the Netherlands; bertiejoan.vanheuven@naturalis.nl (B.J.H.); freek.vonk@naturalis.nl (F.J.V.); martin.rucklin@naturalis.nl (M.R.).
    3 Fachbereich Geowissenschaften der Eberhard-Karls-Universität, Hölderlinstraße 12, D-72074 Tübingen, Germany; i.werneburg@gmail.com (I.W.).
    4 Paläontologisches Institut und Museum, Karl-Schmid-Strasse 4, 8006 Zürich, Switzerland; (M.S.V.).
    * Correspondence: m.k.richardson@biology.leidenuniv.nl (M.K.R.)

    Pit vipers (Crotalinae) are a subfamily of snakes characterized by an infrared-sensing, the loreal pit or pit organ, located bilaterally between the eye and nostril. It functions in prey acquisition, predator avoidance and behavioural thermoregulation. The pit organ consists of an outer and an inner chamber, septated by a heavily innervated membrane. The evolution and development of the loreal pit remain poorly understood. Here, we study the development of the loreal pit in a rare embryo collection of Bothrops jararaca and Calloselasma rhodostoma, using macro-photographing, microCT, 3D-reconstruction and histology. In early development, we find the outer chamber develops as a shallow pit, rostral to the eye and lined with cuboidal epithelium, similar to its flanking epidermis. In intermediate stages of development, we see the inner chamber develops as a pocket rostral to the orbit and dorsal to the initial pit. It is lined with squamous epithelium, similar to the neighbouring corneal epithelium. The two chambers are partly separated by loose connective tissue: the early pit membrane, which is similar to that of the orbital ridge. In advanced stages of development, the loreal pit is similar to the adult morphology and is relatively displaced rostrad as the snout elongates. The pit membrane is heavily innervated by the trigeminal nerve and completely separates the two chambers. We have also found that the loreal pit sheds during ecdysis. Our findings suggest the ancestral loreal pit contained only one chamber, morphologically similar to the labial pits of extant pythons and boas. Our findings also suggest the outer chamber invaginates from the skin, while the inner chamber is derived from the corneal epithelium. To further test this hypothesis we will study gene expression of skin and eye-specific markers, using in-situ hybridisation in freshly-fixed pit viper embryos.