Dimorus

From Memory Alpha, the free Star Trek reference

Dimorus was a planet known for a species of indigenous rodents that had the ability to shoot deadly poison darts.

During the 2260s, while visiting this world Gary Mitchell intercepted one of these darts intended for his friend James T. Kirk. Although he nearly died from the incident, he was able to make a full recovery. (TOS: "Where No Man Has Gone Before")

Dimorus appeared on a star chart in astrometrics in VOY: "Child's Play".