Threat ganglia
Threat ganglia were five pairs of tendrils that extended from the base of a Kelpien's head when they sensed danger. They worked by responding to shifts in the environment, thus acting as an early warning system. Their presence made empathy a defining trait of the species. ()

The vahar'ai was marked by the ganglia inflaming in a manner not otherwise seen. Eventually, they came loose, ending the condition. ()

Ganglia were not the only method a Kelpien had for sensing potentially dangerous individuals and situations. As Saru commented in 2257, even without his ganglia, he still could strongly sense such things intuitively. ()

Notable activations
In 2256, Saru's threat ganglia extended in the prelude to the Battle of the Binary Stars, when the Sarcophagus decloaked. () After the battle, his ganglia began reacting to the presence of Michael Burnham, as he now considered her dangerous – for example, when Burnham did not leave the  on prison shuttle SPT 21 and when he realized she had instead been given the opportunity to remain aboard the ship. () Burnham remarked that his threat ganglia were indicating he hadn't been consulted in this decision and that, since she was only there to be of assistance, he could tell his threat ganglia to relax, though he replied that they still weren't convinced. ()

However, as Burnham also noticed, Saru's threat ganglia did not extend in the presence of "Ripper", which Burnham interpreted as evidence that the animal was not innately dangerous. ()

Following Discoverys arrival into the mirror universe, Saru's threat ganglia extended when Lieutenant , later revealed to be the Klingon sleeper agent Voq, entered the bridge. ()

In the mirror universe, Kelpiens' threat ganglia was considered a treat when cooked. Emperor  fed one, taken from a slave, to Michael Burnham. ()

Learning that who he knew as Captain Gabriel Lorca was actually his mirror counterpart from the Terran Empire, Saru was bemused as to how his threat ganglia never reacted to him. ()

Saru's threat ganglia extended as the Discovery approached Starbase 1; once Discovery dropped out of warp, it was found that the starbase had been seized by the House of D'Ghor. ()

Saru's threat ganglia fell out when he reached vahar'ai. () Afterwards, however, similar protrusions activated when Saru was cornered by a Ba'ul, and they shot darts at the individual. Soon thereafter, Saru's sister, Siranna, and all other Kelpiens on their homeworld of Kaminar experienced their own threat ganglia falling out when they too underwent vahar'ai. ()

Anatomy
Foods