Transparent-blooded fish with no hemoglobin is a unique vertebrate anomaly

Discovery of the World's Largest Fish Breeding Area

In a groundbreaking discovery, a vast nesting ground for the unique white-blooded icefishes has been found beneath the Filchner Ice Shelf in the Antarctic Weddell Sea. This remarkable discovery, announced by Autun Purser of the Alfred Wegener Institute in Bremerhaven, Germany, sheds light on the population and habitat of these alien-like creatures.

The nesting ground, spanning an area of 45,600 square metres, is home to an estimated population of 60 million icefishes. With fish nests three quarters of a metre in diameter, this is the largest breeding area known for these animals to date, surpassing previous observations made with the Ocean Floor Observation and Bathymetry System.

The discovery adds significantly to our understanding of the white-blooded icefish population and their unique habitat. The icefishes, known as Channichthyidae, have had their appearance and physiology altered due to their extreme living conditions. For instance, they lack hemoglobin in their blood, making them the only known vertebrates not to have hemoglobin as adults. This lack of hemoglobin gives them clear blood and a peculiar pale coloration.

The population's survival and thriving in Antarctica's cold and oxygen-rich waters can be attributed to a random mutation that occurred tens of millions of years ago when Antarctica cooled. This mutation allowed them to survive without hemoglobin, and instead, they rely on the oxygen being carried exclusively in physical solution.

The large nesting ground provides valuable insights into the reproductive behavior and population dynamics of white-blooded icefishes. The study on Antarctic icefishes, published in 2003, states that they are a posterchild for what can happen when a species is isolated in an extreme environment.

The proposal to protect this fish spawning area under the Filchner Ice Shelf in Antarctica was made by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) in 2016. However, the Marine Protected Area has yet to be established. The discovery of this large nesting ground emphasizes the importance of protecting the marine environment for the white-blooded icefish species.

The icefishes' altered vision due to living in sub-zero waters is another fascinating aspect of these creatures. Their first appearance in Antarctica marked a significant step into a newly available ecological niche. The study on Antarctic icefishes further highlights the resilience and adaptability of life in the most extreme environments.