Mercury

Often referred to as "Merc" (Mer-kun in the Japanese version). The platoon's messenger-dog, who has a bad habit of biting peoples' heads. He was demoted from Corporal to Courier Private First Class for biting an officer in Episode 1. He is very fast, reliable and sensitive to the emotions of his team. Their reaction to a particularly unpleasant officer (Major Connery) lead to the previously mentioned incident. He resembles a Labrador Retriever.

While Merc is normally seen as a friendly dog with the members of Section III, when events warrant it, he shows himself to be what the commoners referred to as a "military hound," and can even disarm opponents.

(source: Wikipedia)