Meeting Abstract
Notothenioid fishes are the primary taxon of fishes in the Southern Ocean. The Southern Ocean surrounds Antarctica and is isolated by topography, currents, and thermal environment: the water is generally stable between -1.9 and +1°C. Notothenioids have a variable but limited ability to acclimate to temperatures as low as +4°C, therefore, we would expect their nervous system to be sensitive to temperatures in this range. Most putative molecular thermosensors in vertebrates belong to the transient receptor potential (TRP) family of ion channels, but the most cold-sensitive TRP channel thus far characterized activates above +14°C, far above any ecologically-relevant temperatures for notothenioids. We expect molecular thermosensors to be expressed in the trigeminal ganglion because it is the sensory ganglion that innervates the head. To identify candidate molecular thermosensors we dissected the trigeminal ganglion and whole brain from five Harpagifer antarcticus, a notothenioid in the family Harpagiferidae. We extracted the RNA and conducted TagSeq to identify which TRP channel genes were highly expressed in the trigeminal ganglion, and we normalized expression relative to the whole brain to eliminate genes that were generally expressed. We found high relative expression of TRPV1 and TRPM1. TRPM1 has not previously been identified as a thermosensor, but appears to have a gene duplication in notothenioids that could enable evolutionary novelty. TRPV1 is a noxious heat sensor in other vertebrates, sensing in the range of >25°C, a range never experienced by notothenioids. Thus, TRPV1 might be tuned to much lower noxious heat sensation in these fish. Future directions include characterizing the thermosensitivity of this channel using electrophysiology.
