crocodile icefish facts
Crocodile Icefish Facts
Though survival seems highly unlikely in the cold temperatures of the Antarctic, there are vertebrates that have been living there for quite some time now. Icefish are termed one of the most extraordinary creatures of our planet, and this article enlists facts about one of the most popular members of this species - the crocodile icefish.
'Evolution is a tinkerer'. Though originally quoted by François Jacob, this line was again made popular by H. William Detrich III, Principal Investigator of the United States Antarctic Program, after he came across the surprising living mechanism of the crocodile icefish.
Before we jump to facts related to the crocodile icefish, let's first understand what an icefish really is. An icefish is a mammal that is endemic to the cold waters of Antarctica and South America. It belongs to the perciform family, a family of vertebrates that accounts for 40% of all the fish in the world, and falls under the larger suborder Notothenioidei. There are over 132 species of icefish known till now, with high possibilities of new ones being discovered.
| Classification of the Crocodile Icefish | |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Actinopterygii |
| Order | Perciformes |
| Suborder | Notothenioidei |
| Family | Channichthyidae |
Like many of its family members, the crocodile icefish, Channichthyidae also known as the white-blooded fish in many regions, can be found in the freezing waters of the Antarctic and South America. Currently, there are about 25 recognized species of the crocodile icefish.
The crocodile icefish can be found mostly in the Antarctic waters, where temperature falls below -2 to -4°C. Their diet consists of krill, copepods, and other small species of fish. Crocodile icefish can reach a length of 30 to 70 cm.
The crocodile icefish attains sexual maturity between 5 to 8 years, and the mating season starts in autumn and winter. The female is capable of laying almost 10,000 to 20,000 eggs, and the incubation period lasts from 2 to 6 months, depending on the geographic location.
As the blood of a crocodile icefish contains no hemoglobin (the oxygen-binding protein that gives blood its red color), it is transparent and colorless. Red blood cells are rarely found, and if present are defunct. The body's low metabolic rate, and the high solubility of oxygen in the freezing Antarctic waters help the fish to survive without hemoglobin. However, the oxygen-carrying capacity of their blood is 10% less than their distant cousins with hemoglobin.
Instead of hemoglobin, the crocodile icefish contain larger blood vessels and capillaries, bigger hearts, and great blood volume as compared to other fish. Coronary arteries are missing, and ventricles are extremely squishy, helping them to absorb oxygen directly from the blood they pump.
Despite being in such freezing waters, the blood of a crocodile icefish never freezes because its body produces its own antifreeze. Trypsinogen, a pancreatic digestive enzyme that breaks down proteins in food, found in other vertebrates has been transformed to be distributed throughout the body to prevent the blood from freezing.
Even though the icefish has survived the harsh stages of evolution, it now faces a threat which has the capacity to make it extinct – man-made climatic changes. Due to the excessive use of fossil fuels and rising pollution levels, the Southern Ocean is getting warmer, more acidic, and less nutritious. Icefish are extremely sensitive to high temperatures, and if the temperature of the oceans continue to rise, future generations might not witness this amazing oceanic species.