Such zoological park district established as provided for in Section 55-21-3 shall establish a district zoological park and garden board which shall supervise and control the zoological park. The district zoological park and garden board, hereinafter referred to as the board, shall consist of three (3) representatives from each participating county. Each member shall be appointed by the governing authority of the entity he represents for a term of six (6) years and until his successor is appointed and qualified.