What special function does the spleen of the seal do

The spleen of the Arctic Weddell seal contains so much extra oxygenated blood that it often is referred to as a SCUBA tank; in fact, the release of red blood cells into the circulation is so tightly regulated that arterial oxygen content doesn't decrease for the first 15–18 min underwater.

D.) domain, kingdom, phylum, class, order, family, genus then species