Date of Award:

8-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Committee Chair(s)

Alan H. Savitzky

Committee

Alan H. Savitzky

Committee

Sara Freeman

Committee

Susannah French

Committee

Molly Womack

Committee

Kerry Jordan

Abstract

Boas and pythons use specialized sense organs called pit organs to detect radiant heat. Pit organs in these lineages occur in paired arrays along the upper and lower jaws and are served by the trigeminal nerve (the fifth cranial nerve and one of the largest). Information from the pit organs travels via branches of the trigeminal to the brain and ultimately is processed in the optic tectum, along with information from the visual system. That means these snakes effectively “see” heat. While studies of the pitviper infrared-imaging system are numerous, very few studies of this system in pythons or boas exist, and those only include a few species in each family. The goal of this dissertation was to compare the anatomy of structures critical to the IR-imaging system in boas and pythons (with an emphasis on the nerves and blood vessels) and examine its development in pythons. In Chapter 2, I used histology and micro-computed tomography (microCT) of python embryos to examine variation in the timing of development of structures associated with IR-imaging, including the pit organs, trigeminal nerve, and optic tectum. I found that the pits of the upper and lower jaw do not follow the same developmental timing. In Chapter 3 I used microCT scans of different species (four pythons and two boas) to examine the shape and size of their pit organs and their relationship to the nerves that supply them. I found substantial differences in sub-branching of the trigeminal and the pits they serve between all species examined. Some of the pit organs were served by multiple sub-branches of the trigeminal, suggesting a more complex mapping of thermal information in the brain than previously reported. In Chapter 4, I used microCT to examine the fine structure of blood vessels serving the pit organs. The microvasculature underlying the pits is consistently complex, but its density and extent varies among the species. Blood vessels underlying the pits presumably help to maintain a constant temperature of the IR-sensitive tissues, thereby improving their ability to detect heat.

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