The eight individuals were charged with murder and conspiracy to murder, according to court documents seen by AFP.
Lotter, a 51-year-old South African conservationist, was a founder of the PAMS Foundation which worked to stop the poaching of elephants and trafficking of ivory in Tanzania. He was killed by unknown gunmen on August 16 while in a taxi on his way back from the airport.
"We congratulate the Tanzanian Police Force for the arrest and charging of these individuals," PAMS said in a statement.
PAMS had scored some big wins fighting the illegal wildlife trade, working with Tanzania's National and Transnational Serious Crimes Investigation Unit (NTSCIU) in the arrest of nearly 900 poachers and ivory traders.
These include Chinese citizen Yang Fenlan known as the "Ivory Queen", who is currently on trial in Tanzania for illegally trafficking 706 elephant tusks between 2000 and 2014.
Tanzania has been one of the African countries worst hit by elephant poaching, losing over 66,000 elephants in a decade, but interdiction efforts meant poaching has declined in recent years.