Octopus have a different special protein called haemocyanin, which makes their blood blue, and the ice fish doesn't have either hemoglobin or the haemocyanin which is why the blood runs clear.

章鱼有一种不同的特殊蛋白质，叫做血青素，这使它们的血液呈蓝色，而冰鱼既没有血红蛋白，也没有血青素，这就是为什么血液是透明的。