Who is Oyster in the novel, The Amazing Adventures of Kavalier & Clay?

Oyster is the name of a sled dog at the Kelvinator in Antarctica. Oyster saves Joe's life at least twice, including when Oyster is sleeping with Joe, and whines when carbon monoxide gas accumulates after a stove breaks. Later, Shannenhouse kills Oyster, much to Joe's regret, to use its pelt to refurbish a plane at the base.