Legacy of Aru Kararu Al Caral no Isan

In the 26th century, humans discover a humanoid race living on the distant world GO/7498/2, a dark-skinned, golden-eyed people who seem to eke out a primitive, carefree existence. However, a scout team from Earth discovers that there is more to them than meets the eye–they live in symbiosis with vicious reptilian parasites, and the Terran scientists have upset the delicate natural balance.

(Source: The Anime Encyclopedia)