Final answer:
Icefish adapt to their hemoglobin-less condition by efficiently absorbing dissolved oxygen directly from their cold, oxygen-rich aquatic environment through enhanced circulatory and gill structures.
Step-by-step explanation:
The icefish, an animal with white blood lacking hemoglobin, has adapted to cold, oxygen-rich Antarctic waters. Unlike humans and most vertebrates, which rely on hemoglobin in red blood cells to transport oxygen, icefish survive thanks to unique physiological adaptations that allow them to absorb oxygen directly from the water. Their large gill surface area, high blood volume, and a heart that pumps a large volume of blood enable them to make the most of the oxygen dissolved in the water. Other invertebrate species use various respiratory pigments like hemocyanin or hemerythrin to bind and transport oxygen. Icefish take advantage of their habitat's high oxygen availability and their adaptations to overcome the lack of hemoglobin as an oxygen carrier.