On December 1, 1927, zool­o­gist Ditlef Rustad pulled ashore on Bouvet Island, 1,750 kilo­me­ters off the coast of Antarc­tica, as part of a Nor­we­gian expe­di­tion to claim the remote, wind-​​whipped island as a whaling out­post. Later that month, casting nets into the frigid waters, Rustad hauled up a very strange-​​looking fish. It had no scales and was very pale, even translu­cent in parts. Behind its pro­truding, crocodile-​​like jaw, he saw gills that were milky instead of the usual crimson. And when Rustad cut open the fish, he saw that its blood was trans­parent, like ice water. “Blod farvelöst,” he wrote in his notebook—“colorless blood.”

In a 1954 Nature paper, bio­chemist Johan Ruud con­firmed that Chaeno­cephalus acer­atus lacked red blood cells and hemo­globin, the pro­tein that car­ries oxygen around the body and gives blood its red color. “It was a shocking dis­covery,” says William Det­rich of North­eastern Uni­ver­sity, who has spent most of his career studying C. acer­atus and the other 15 rec­og­nized species in the family Chan­nichthyidae, or the Antarctic ice­fishes. “Among the 50,000 or so species of known ver­te­brates, these fish are the only exam­ples that lack both hemo­globin and red blood cells.”

Read the article at The Scientist →