Threat ganglia were five pairs of tendrils that extended from the base of a Kelpien's head when they sensed danger.

In 2256, Saru's threat ganglia extended in the prelude to the Battle of the Binary Stars, when the Sarcophagus decloaked. (DIS: "The Vulcan Hello") 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 USS Discovery on prison shuttle SPT 21. (DIS: "Context Is for Kings", "The Butcher's Knife Cares Not for the Lamb's Cry")

However, Saru's threat ganglia did not extend in the presence of "Ripper", which Burnham interpreted as evidence that the animal was not innately dangerous. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry")

Following Discovery's arrival into the mirror universe, Saru's threat ganglia extended when Lieutenant Ash Tyler, later revealed to be the Klingon sleeper agent Voq, entered the bridge. (DIS: "Despite Yourself", "The Wolf Inside")

In the mirror universe, Kelpiens' threat ganglia was considered a treat when cooked. Emperor Philippa Georgiou fed one, taken from a slave, to Michael Burnham. (DIS: "Vaulting Ambition")

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. (DIS: "What's Past Is Prologue")

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. (DIS: "The War Without, The War Within")