Salarians

Mass Effect, Mass Effect 2 & Mass Effect 3
The second species to join the Citadel, the salarians are warm-blooded amphibians with a hyperactive metabolism. Salarians think fast, talk fast, and move fast. To salarians, other species seem sluggish and dull-witted. Unfortunately, their metabolic speed leaves them with a relatively short life span; salarians over the age of 40 are a rarity.

The salarians were responsible for advancing the development of the primitive krogan species to use as soldiers during the Rachni Wars. They were also behind the creation of the genophage bioweapon the turians used to quell the Krogan Rebellions several centuries later.

Salarians are known for their observational capability and non-linear thinking. This manifests as an aptitude for research and espionage. They are constantly experimenting and inventing, and it is generally accepted that they always know more than they're letting on.