Sharks are a group of elasmobranch fish whose ability to detect painful stimuli is debated. Painful chemical, thermal or mechanical stimuli are mostly transmitted through unmyelinated (or thinly myelinated) sensory nerve fibres with small diameter cell bodies in the dorsal root ganglia. However, a previous study demonstrated that black-tipped shark dorsal root ganglia show a lack of small diameter sensory neurons implicating that the shark are unable to feel painful stimuli. We replicated and extended this finding in Bamboo sharks to show a lack of unmyelinated C-fibres in fin nerves and existence of an unique group of large diameter sensory neurons. In apparent contradiction, we found staining of shark sensory neurons with anti-CGRP, a pain protein. Therefore, we hypothesize that sharks express pain proteins and are able to behaviorally react to painful stimuli using adaptations in the large diameter neurons, which in general serve as light touch sensors. In the Grass laboratory, I would like to establish behavioral phenotype of pain-sensing in hatchlings of catsharks as well as functionally characterize the response of shark sensory neurons to noxious stimuli such as acid, high temperature and mechanical probing. I expect that the shark hatchlings to show avoidance or freezing behavior to the noxious stimuli along with hyperexcitability of their sensory neurons. This project will shed light for the first time on pain-sensing adaptation in these evolutionarily ancient fish.