Over: Knut E. Jørstad in action with genetic analyses on board G.O.Sars. (Photo: Leif Nøttestad)
Originally, our electrophoretic equipment was designed for conducting genetic analyses of proteins onboard research vessels during ongoing surveys, but it was quite uncertain how it would actually work under the weather conditions in the Antarctica. And the experiences so far during the ongoing survey – this work excellent, even under bad weather with wind force between 20 – 26 m/s (40-50 knots). Both the organization of the laboratory on the G.O. Sars and its good stability are important elements for performing successful analyses. In addition, the use of a small, transportable “gyro table” from the fish laboratory was extremely useful in bad weather conditions, especially on different critical stages in the analyses. A similar approach with ”gyro tables” is needed on all our research vessels!
Samples of Antarctic krill, Euphausia superba, have so far been collected from 11 trawl stations, whereas 5 samples were from stations taken in the first survey period before changing the staff in Cape Town. The samples from 8 stations, constituting nearly 800 individual krill, have now been analysed onboard for 5 different enzymes. The results demonstrated significant genetic variation for 3 of the enzymes investigated, and the data obtained can now be used in detailed statistical comparisons of genetic profiles between samples and geographic separated areas. One example of genetic variation is given in the picture, which show various banding patterns expressed for the enzyme lactate dehydrogenase in krill muscle tissues. In all sample collections / trawl stations the individual krill is identified to genetic type based on the specific banding patterns for the enzyme in question. Then the frequencies of the genes corresponding to the various banding patterns in the particular samples are calculated and further use in the statistical comparisons. In addition to the protein analyses conducted on board, samples for various DNA analyses have been collected from the same trawl stations. These samples are preserved in ethanol and will be analysed in Bergen after the survey.
Example of genetic variation detected for the protein - lactate dehydrogenase - in Antarctic krill, Euphausia superba. The different banding patterns shown are genetically determined. The banding pattern in the lower part of the picture, have not been described in earlier studies. The protein variation, as well as modern DNA techniques, is in common use for identification of populations. (Photo: Leif Nøttestad)
The G.O. Sars survey is covering a very large area, and krill samples have been collected from the area around South Georgia to Bouvet Island, supplemented with the region south to ”Astrid-ridge” near Dronning Mauds Land on the Antarctic continent. The overall sample collection will be analysed both for protein variation and various DNA markers. The results will be used in statistical tests to reveal if only one or several krill populations with their own gene profiles exist within the large area investigated. Such information represents fundamental knowledge, necessary for developing a sustainable management of the most important krill species in this area.
The krill species Euphausia superba is also distributed in the other oceans around the Antarctic continent. The results from earlier genetic analyses are fragmented and often controversial. Recently, the DNA methods developed are providing new tools to be used in more detailed genetic investigations, and such studies will possibly result in more conclusive knowledge. Clearly, detailed genetic comparisons of gen profiles from samples of krill collected from the complete distribution area around the Antarctic continent are needed. This can only be achieved through comprehensive international genetic investigations between institutions and nations that are interested to harvest and conserve the enormous krill resources in the area. Thus the genetic studies now conducted on G.O. Sars could represent one step towards the development of international cooperation, aiming on the establishment of a common model of the genetic structure of krill in the Antarctic.
Knut E. Jørstad is senior scientist in the research group ”Population genetics and ecology”, and he has long experiences in genetic studies of many marine species, including crustaceans. On the G.O. Sars survey he is responsible for collection of samples (krill and ice fish) for DNA analyses and for conducting protein analyses onboard the ship during the actual survey.