To counter the ingestion of excess salts, marine teleost fish have specialized cells in their gills that pump _ ions into the surrounding seawater. As these ions leave the fishes' bodies, they create an electrical gradient that is balanced when _ ions leave their bodies as well.

Question

To counter the ingestion of excess salts, marine teleost fish have specialized cells in their gills that pump _____ ions into the surrounding seawater. As these ions leave the fishes' bodies, they create an electrical gradient that is balanced when _____ ions leave their bodies as well.