If You’re in the Infrared, You’re Dead: Molecular Mechanisms of Predation and Infrared Sensory in Snakes

There are over 3000 snake species that have been identified worldwide, and about 600 of those species are poisonous¹. All snakes possess interesting physiological characteristics bearing biologically important questions about snake morphology that continues to promote research about how snakes move, their evolution, how some snakes create and use their venoms, how snakes capture their prey and its relative importance to benefitting human society. In an article published March 2010, Molecular Basis of Infrared Detection by Snakes, by Elana O. Gracheva et. al, Gracheva, she and her team attempt to answer some of these questions by studying how venomous pit vipers are able to use their unique pit sensory system to detect their prey by utilizing infrared radiation.

Most people are aware of simple snake anatomy: they are legless reptiles with scales that literally ‘snake’ their way around. In the article, the authors introduce the reader with information about how pit vipers detect their prey, without intimidating the reader with overly complex concepts or science jargon, peaking the reader’s curiosity as to how snakes are able to detect their prey.

“Snakes possess a unique sensory system for detecting infrared radiation, enabling them to generate a ‘thermal image’ of predators or prey. Infrared signals are initially received by the pit organ, a highly specialized facial structure that is innervated by nerve fibers of the somatosensory system. How this organ detects and transduces infrared signals into nerve impulses is not known.”

Needless to say, the article doesn't fail to bring their audience to a higher concepts and biological understanding to support their research and present their methods for testing the actual molecular mechanisms of the pit organ, building on existing research that pit vipers possess infrared sensory organs that aid in hunting their prey. The authors provide detailed information about trigeminal fibers to clearly explain their reasoning and how it directed their research to focus on transcriptome profiling to identify TRPA1 as a “candidate infrared detector” based on how infrared radiation can be detected and the limited genome information of pit vipers.

TRPAs are transient receptor potential cation channels that are present in human cells and many animal cells, including snakes. In humans, the receptor is primarily responsible for the detection of pain, cold and environmental irritants. In snakes, they detect infrared radiation. The authors compared trigeminal ganglia (TG) and dorsal root ganglia (DRG) anatomy of pit snakes to those of humans and other snakes that lack pit organs, and compared their gene expression profiles, noting that TG fibers in pit snakes are larger while gene expression profiles are fairly similar to those of humans, thus “marked differences in snakes should reflect functional specialization associated with infrared detection.” By using sequencing to compare profiling between TG and DRG, they found that TRPA1 channel in the diamondback rattlesnake was “was enriched 400-fold in TG” and that they lacked transcripts for TRPA1’s in their DRG, supporting their hypothesis that TRPA1 plays a critical role in the function of infrared sensing in the TG. The authors used high resolution imaging to illustrate these findings, enhancing the readers’ understanding and appreciation for the dense information presented. It also leaves the reader wondering if human gene sequences similar to those of TG fibers in pit snakes could be enhanced to give us truly superhuman power. Maybe flashlights would go extinct and our children would gawk at them in museums.

Overall, the authors do a good job of explaining their research and presenting information that supports their hypothesis that TRP channels are responsible for infrared radiation detection in certain snakes species and why infrared radiation detection is not possible in other species with TRP channels. Despite the explanation, I still couldn't stop wondering if human gene sequences similar to those of TG fibers in pit snakes could be enhanced to give us a truly superhuman power. Maybe flashlights would go extinct and our children would gawk at them in museums. After all, the article isn't convincing enough. It doesn't prove TRP channels are solely responsible for the unique infrared radiation ability to capture prey, exactly how it evolved or why it evolved in certain species with TRP channels than others. The research has a lot of potential, and the outcomes and additional research that it could promote were not discussed in the article’s discussion. The only obvious ‘benefits’ of this research that were apparent to me seemed to concern the development of modern warfare and weapons. The article could have offered information on why this research was important and its implications rather than implying that the research was motivated by science not knowing why or how infrared radiation detection functions. Although human curiosity is great, research is expensive, and some of the motives for the research and greater analysis and discussion of its significance would broaden the reader’s understanding and probe the scientific community to continue researching such a fascinating topic that has been relatively dormant for half a century.

Posted by: Karen-Maria Melendez (2)

References:

1) http://apps.who.int/bloodproducts/snakeantivenoms/database/

2) Gracheva, Elena O., Nicolas T. Ingolia, Yvonne M. Kelly, Julio F. Cordero-Morales, Gunther Hollopeter, Alexander T. Chesler, Elda E. Sanchez, John C. Perez, Johnathan S. Weissman, and David Julius. "Molecular Basis of Infrared Detection by Snakes." Nature 464.1006-1011 (2010). http://www.nature.com.silk.library.umass.edu/nature/journal/v464/n7291/full/nature08943.html