 |
| 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
