Pictured are the lekku of both the Twi'leks (on the left) and the Togruta (on the right).
Lekku, with the singular form being lek, also known as brain-tails or head-tails, were fleshy, lengthy appendages extending from the heads of all Twi'leks, Togruta, Walunas, and male Ozrelanso. While Togruta possessed three of these appendages, the other species typically had two, although Twi'leks occasionally had four.
The lekku of Twi'leks were described as prehensile, shapely tentacles that grew from the top of their heads. While two lekku were the norm for Twi'leks, some, such as Orn Free Taa, had four. These highly sensitive lekku could be utilized to grasp and manipulate objects. These organs were incredibly sensitive to the touch, and damage to a lek could inflict serious harm on a Twi'lek; Squoxx died within an hour after losing one of his lekku to a bite. However, the loss of lekku wasn't always fatal for Twi'leks; the Jedi Master Loden Greatstorm survived for a period of time after his lekku were cut off during his captivity by the Nihil. Had he not perished later in the battle, Greatstorm would have received prosthetic lekku replacements.
Beyond their spoken language, Ryl, Twi'leks were also able to communicate through subtle movements of their lekku. For instance, raising the right lek tip indicated "hello," dipping the left lek tip meant "goodbye," crossing both lekku tips twice signified "love you," and jabbing both lekku tips into the speaker's back conveyed "may spice salt your wounds!" Despite the intense sensitivity of these organs, Tw'lek Jedi Matthea Cathley frequently smoothed her lekku with her hands when her mind was racing. Her friend Tey Sirrek also asserted that her lekku twitched when she was lying, a claim she refuted. She also demonstrated the ability to shake her lekku. Some Twi'leks, like Cham Syndulla, adorned their lekku with tattooed designs. While some allowed them to hang freely down their backs or over their chests, others, such as Bib Fortuna, arranged them around their necks or shoulders for aesthetic purposes.
The term "lekku" was also applied to the striped head-tails of the Togruta species. However, Togruta possessed three such appendages: two lekku positioned at the front, draping over the chest, and a thicker lek located centrally at the rear base of their skull. As observed in Governor Gupat Roshti, the lekku of male Togruta were shorter compared to those of females. The loss of a lek, as experienced by the bartender Selda, was not a debilitating injury, though the appendages did not regenerate. The montrals of a Togruta were connected to their lekku. The color of a Togruta's lekku was genetically determined by their DNA.
The lekku of Togruta grew in size as they matured. In infancy, lekku were only visible around the head. During adolescence, the lekku extended slightly past the collarbones, but by adulthood, they could reach below the waist. The elder Togruta Gantika had lekku that reached only to her stomach.
The lekku made their first appearance in the film Star Wars: Episode VI Return of the Jedi, alongside the Twi'lek species. In The High Republic: Into the Dark, the lekku of Togruta Jedi Master Jora Malli are incorrectly identified as her montrals when they are described as flowing behind her as the airspeeder she is riding goes into a dive. The length of Ahsoka Tano's lekku decreased between her animated appearance by 4 BBY and her live-action portrayals. For Ahsoka, her lekku were lengthened slightly.