The icefish: The benefit of living in cold water

Chionodraco hamatus (Marrabbio2 2006)

Organisms live in all kinds of environments from the Antarctic to volcano geysers. But how did they adapt? And what costs and benefits did they aquire by adapting to extreme environments?

A classic example of an adaption to an extreme environment is the icefish (family Channichthyidae). The icefish are a family of near translucent fish that live in the ­­­­southern ocean in Antarctica.  The  icefish share an antifreeze protein that allows them to survive in water temperatures of -1.9 degrees celcius (chen et al 1997).

Icefish with diver, (science notes 2006)

The adaptation

The Icefish (suborder notothenioidei) have an antifreeze protein that has evolved from the mutation of a gene that coded for a pancreatic enzyme into a gene that coded for an antifreeze protein (Chen et al 1997). 

This has given the icefish and other Antarctic species the benefit of being able to survive in a cold environment with no competition from temperate fish. The cold waters are also oxygen rich which allows the Channichthyidae family to survive despite their lack of hemoglobin (Montgomery and klements 2000).

  Chionodraco rastrospinosus (Loeb 2011)

Disaption

The Channichthyidae family do-not have red blood cells. This has reduced their oxygen carrying capacity to one tenth of normal haemoglobin fish (coppe et al 2012). According to Montgomery and klements (2000) the loss of the haemoglobin phenotype is generally regarded as a disaption because there is still selection for haemoglobin genes. However the cost benefit ratio of having haemoglobin is still unclear (Montgomery and klements 2000).  It is speculated that the loss of the haemoglobin phenotype may be due to gene mutation or a bottleneck event (Coppe et al 2012).

Chaenocephalus aceratus(British antarctic survey, 2009)

Recovery

The icefish have evolved a number of traits to meet their oxygen needs without hemoglobin.  These include an enlarged heart and veins and extra venation for more circulation, a slower metabolism and oxygen uptake through the skin. They also have higher mitochondrial densities to create more energy (Coppe et al 2012).

Thankyou for reading :) 

References:

Chen, L, DeVries, AL, Cheng, CC 1997, evolution of antifreeze glycoprotein gene from a trypsinogen gene in Antarctic notothenioid fish, Proceedings of the national academy of science, vol.94, pp.3811-pp.3816. url:http://www.pnas.org/content/94/8/3811.full accessed: 3.3.16

Montgomery, J, Clements, K 2000, ‘Disaptation and recovery in the evolution of Antarctic fishes’, TREE, vol. 15, no.7, pp. 267 – pp. 271

Coppe, A, Agostini, C, Marino, IAM, Zane, L, Bargelloni, L, Bortoluzzi, S, Patarnello, T 2012, ‘Genome Evolution in the Cold: Antarctic Icefish MuscleTranscriptome Reveals Selective Duplications IncreasingMitochondrial Function”, Genome biology and evolution, vol.5, no. 1 pp. 45-60. Doi: 10.1093/gbe/evs108url: http://www.ncbi.nlm.nih.gov/pubmed/23196969 accessed: 3.3.16

Image sources: 

British antarctic survey 2009, fishbio.com url:http://fishbio.com/field-notes/ocean-bay-delta/carnivorous-largemouth-icefish-dominate accessed 5.3.16

Science notes 2006, sciencenotes, url: https://sciencenotes.wordpress.com/2006/09/25/icefish-of-antarctica/ accessed: 5.3.16

Marrabbio2 2006, wikipedia commons, url:https://commons.wikimedia.org/wiki/File:Icefish_Chionodraco_hamatus.jpg accessed: 5.3.16

Loeb, V 2011, NOAA, url: https://commons.wikimedia.org/wiki/File:Chionodraco_rastrospinosus.jpg accessed: 5.3.16