MARINE BIODIVERSITY AND ECOSYSTEMS

Unique fat transport in Antarctic fish - cold adaptation?

Investigator: Victoria Metcalf
Organisation: School of Biological Sciences, University of Canterbury

What I do: I’m a biologist interested in Antarctic fish and how they function. My area of biology is known as functional genomics- a combination of molecular biology, evolutionary biology and biochemistry. My research examines molecular and physiological differences between organisms and also uses these differences to learn more about how animals function in their environment (envirogenomics).

My current research aims to try and understand more about lipid (fat) metabolism and in particular, lipid transport in Antarctic fish.

Why I do it: Antarctic fish are fascinating animals and a group of fish called notothenioid fish dominate Southern Ocean waters. What has allowed these fish to rule is their substantial adaptation to the frigid waters they inhabit. For example, their blood is very different to the blood of other fish. They have large amounts of antifreeze proteins. This makes their blood thicker, so some species lack red blood cells to compensate.

Another adaptation of notothenioid is that they tend to have more fat. This helps them achieve buoyancy because they don’t have swim bladders. The metabolism of lipid is also their main source of energy. From a consumer’s perspective, the lipid is of interest because of its high nutritional value.

Currently I am investigating how lipids are processed by Antarctic fish. For example, very little is known about how Antarctic fish transport fatty acids in their blood. Humans and other mammals (and most fish) use a protein called albumin. However, I have previously shown that there has been a loss of albumin in one Antarctic species, the Antarctic toothfish (Dissostichus mawsoni). Fatty acids are instead carried by another protein called high density lipoprotein. The loss of albumin in the toothfish may be a means of further reducing blood viscosity, aiding this species’ survival in subzero water temperatures. 

To investigate this finding further, I am using biochemical and molecular biological approaches to determine if loss of albumin is common amongst Antarctic fish and how this loss has occurred. Increased knowledge about this unique feature of notothenioids will give improved understanding of these fish as well as the biodiversity of the region. Lipid metabolism is very poorly understood in vertebrates. This work will provide significant new knowledge about the mechanism of lipid transport in Antarctic fish, which can also be extrapolated to vertebrates in general.

Aside from time at the laboratory bench, my research involves fieldwork down in Antarctica, primarily to fish for samples.

Some things I’ve found out so far: It looks like lack of albumin is a common state in notothenioid fish, with all species so far examined lacking albumin and instead using high density lipoprotein. However, there are differences in the blood profiles of the different species examined and naturally there is still plenty more work to do.