The six gill shark is
a globally distributed deep water sharks that is found circumglobally. In the
Mediterranean Sea it is caught often by bycatch by fishermen. In this study
genetic variation of the Sixgill sharks of the Mediterranean were assessed and
compared to sharks caught outside of the Mediterranean. The genetic
connectivity between all the sharks was determined and it was shocking to find
that worldwide there was a genetic heterogeneity. By studying the mitochondrial
DNA sequence in a specific area in two specific genes, it was found that of the
total world population there were sub populations between the Pacific Ocean and
the Atlantic Ocean.
Again
like last week’s article the discovery of separate stocks worldwide is vital to
designing management plans for the overall conservation of this species. The
mtDNA analyzed was from 3731bp to 3914bp, this was chosen because it was the
most control of all regions in genes of the sharks. The study brought to light
22 different haplotypes, so in essence twenty two groups
of genes that were inherited together from a twenty two different single
parents. The examination into this shows that over specific geographical
separations such as the mid-Atlantic ridge and most abyssal plains, there is a
clear cut in the data that shows some haplotypes staying with specific unique areas.
In
conclusion the importance of genetics in this study is that without it the
separation and the discovery of multiple stocks of Sixgill sharks has made it
so scientists worldwide can manage the stocks even better. The haplotypes were
found to be not randomly distributed but clustered according to geographically
origin, and actually confined to specific sample locations. Without the
exploration into the genetics of the shark and using the mitochondrial DNA what
was found would not be known.
The
amazing part is during this study on top of the discovery of separate
geographically specific stocks scientists also found that there was no pelagic
life stage, this was found by looking at how the mtDNA shapes in the early life
history of the elasmobranch. The theme of the paper is that there is entire
species that are genetically diverse and by looking at genes it shows that the
populations are subdivided into genetically distinct units separated from each
other by unique bottom structure. 
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