Arkonians did not appear to have sweat glands, and their bodies' hydration system is not based on water. Instead they drink a brown liquid that they call "tarratt-aash". Their saliva has healing properties, as it can quickly repair skin abrasions. Their cellular structure is not capable of handling rapid temperature changes.
In the early-2050s, the Arkonians achieved warp capability. The Vulcans soon made First Contact with them, but it wasn't incredibly successful. They proved to be suspicious and deceitful, and the Vulcans were soon recalled.
In 2152, the Arkonians made first contact with Humanity through Enterprise NX-01. Captain Khata'n Zshaar had been sent to patrol a system the Arkonians had annexed, and sent a shuttle piloted by Zho'Kaan to investigate a human shuttle that had been sent. When both disappeared, the Arkonians and Enterprise had to work together to find their lost crewmen. (ENT: "Dawn")