In addition to being the first Group I intron reported for any animal, the shark introns are also unusual in their chromosomal location. In sharks, the introns do not occur inside the ribosomal RNA genes as they do in other organisms, but instead are found in the DNA spacer regions that separate the ribosomal RNA genes. The discovery of these shark spintrons prompts many questions regarding their acquisition, function, and evolution. We are conducting biochemical studies to determine the function of these spintrons, and exploring the evolutionary basis for the acquisition and distribution of these structures in divergent elasmobranchs. A recently initiated study in our laboratories involves examining global genetic structure in the blue shark.
Blue sharks are a highly migratory species with a circumglobal temperate and tropical distribution.
In the North Atlantic, tagging studies conducted by the APP indicate that blue shark migrations are extensive and seem to follow current patterns in the Atlantic basin. The full extent of blue shark global migrations, however, is unknown. We are using mitochondrial and nuclear DNA sequences to assess global genetic population structure in blue sharks, and the degree of gene flow within and between oceanic basins. Such studies will, we anticipate, improve our understanding of migratory patterns and reproductive behavior in this species. We would greatly appreciate any help from participants in the NMFS Cooperative Shark Tagging Program.