Genomics and Venomics of the sexually dimorphic Temple Pitviper

We invited Dr Ryan McCleary, Postdoctoral Researcher at Utah State University, to contribute a guest writeup about the effort to sequence the genome of the Temple Pitviper.

The Temple (or Wagler’s) Pitviper, Tropidolaemus wagleri, is a venomous snake found in tropical Asia, from southern Thailand; through peninsular Malaysia and Singapore; and into Indonesia (Sumatra and nearby islands). It belongs to the family Viperidae and subfamily Crotalinae (the pit vipers), which have the common characteristics of enlarged, front-rotating fangs and heat-sensing facial pits. The Temple Pitviper itself is extremely unique.

©Herpetological Society of Singapore
A male Wagler’s Pitviper from one of the HSS Herp Walks

Although most snakes have very minor differences between the sexes (what we call “sexual dimorphism”), the Temple Pitviper’s differences are extreme. The females get fairly large-bodied and have colorful spots over their surface, with white, yellow, green, and blue speckling over a black background with yellow bands. The males, on the other hand, are much smaller and narrower in girth, with a fairly uniform light green color and white and/or maroon spots or bars down the body. They are so different that it is really easy to mistake them as being different species. What is even more incredible is that both males and females start off looking the same…like little males! How the change occurs over time is really not known, nor is when exactly it happens.

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Female Wagler’s Pitviper, Photo by Serin Subaraj

Besides the sexual dimorphism, Temple Pitvipers also have a unique venom. Like many vipers, the venom is quite complex, with many different types of toxic proteins present. However, the Temple Pitviper is the only species known to contain a specific family of proteins, the waglerins, in its venom. These waglerins are relatively small (compared to many other toxin protein families) and function as extremely selective inhibitors of neuromuscular activity. It is because of this activity that their venom is currently being studied for potential use in human medicine.

Many Singaporeans may also be familiar with this snake because it is an abundant resident of the Temple of the Azure Cloud (Snake Temple) in Penang, Malaysia. In the Temple, the snakes go about their business unhindered by humans and vice versa. These snakes also rarely bite humans in nature.

We are interested in many aspects of this snake, starting with its natural history and going all the way through the evolution of its venom. We are interested in the genetic basis of the size and coloration differences between the sexes and how this relates to the habits of the species in nature. Do they consume different prey?

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Photo by Noel Thomas

Do they inhabit slightly different microhabitats? Is there a sex-based difference in venom composition? The genome will help us to understand the mechanisms by which these snakes produce their venom and exactly what compounds may be found in the venom, including some that may be used as leads for the development of human pharmaceuticals or research tools. Besides this, there are currently two other snake genomes that have been undertaken—the Burmese Python and the King Cobra. The addition of the Temple Pitviper will expand our understanding of snakes in general and venomous snakes in particular, both in terms of their evolution and their relationships with each other.

There is a lot to do before we can answer these questions, but we currently have a great opportunity. Although we have begun the sequencing of the genome, we have not yet utilized an extremely powerful tool known as PacBio sequencing, due to constraints on funding. This type of sequencing is very important to include for various reasons, but one way to think of it is that the normal sequencing is a bunch of puzzle pieces – with no direction and lots of time, you can still make the picture look right. However, PacBio sequencing is like having the photo on the puzzle box to help guide you and make things a lot easier. Pacific Biosciences (the creators of PacBio technology) have selected our project as one of five (out of 200+ applicants) to compete for complimentary PacBio sequencing, but we need your help!

If you would like to see our project—the only project from Singapore and the only one utilizing a herp species—succeed, you can help by voting for us. The winner of the competition will be selected by popular vote. Anybody can get on the website and vote once every day through the end of the competition (5 April 2017) using up to three different e-mail addresses per name.

Photo by Noel Thomas


The website for our project, which includes a video, can be found at:
We have a Facebook page at:
And a Twitter feed at:
@TemplePitviper or #TemplePitviperGenome

The competition is stiff, and we need every vote we can get. Thanks for helping!

Ryan McCleary
Postdoctoral Researcher
Utah State University (previously with National University of Singapore)