Did you know? ..... The Icefish does not have any red blood cells!

It had been a longstanding dogma in biology that all vertebrates have red blood that contains red blood cells. The main function of the red blood cells is to transport oxygen from the lungs to the different cells throughout the body, and hence it is critical for survival. However, this dogma was challenged on a cold winter day in December 1927, when the Norwegian marine biologist Ditlef Rustad pulled up a strange pale fish from the Antarctic ocean: a fish that had colorless blood! It was during the "Norvegia expedition", set to explore the Antarctic ocean waters, that Rustad, as part of his scientific fieldwork, made this astonishing discovery. This fish, initially named "The Crocodile Fish" ("Krokodille fisk") by Rustad, and later known as the Icefish, has since then been studied by several scientists (including Dr. H. William Detrich), in order to elucidate the secret of how an animal can survive without red blood cells.

"The Icefish". Photo by Ditlef Rustad, 1927 (source: Private). The fish in this photo was kindly identified by Dr. H. William Detrich as the "species Chaenocephalus aceratus, known commonly as the Blackfin icefish". 

Short article in "The Scientist" about the discovery of the Icefish

The popular science magazine "The Scientist" published an article about the discovery of the Icefish.

Short film about the discovery and significance of the Icefish

This discovery is featured as one of the topics for educational movies on evolution, created by HHMI, produced by the acclaimed producer Sarah Holt, and with the well-known evolutionary scientist Sean B. Carroll as the narrator:

"The Birth and Death of Genes - The Story of the Icefish":

This is part of a series of short films in "The Making of the Fittest" Trilogy on evolution. You can read more about these short films, and other educational resources provided by HHMI here.

You can watch the video as live streaming through the above link, or you can request a free DVD copy here.