Tako Luka (たこルカ) is an officially recognized derivative of Megurine Luka, she had a very important involvement in the Vocaloid fandom, most notably in the Japanese community.
She is the result of creativity of imagining Luka's hair in the form of an octopus, in the same manner as Hachune Miku.
Tako Luka shares pretty much the same voice as (or high pitched) Luka herself, regardless of voice bank.