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THE QUEBEC REGION BULLETIN
DÉCEMBRE 2010 - JANVIER 2011/VOLUME 13/NUMÉRO 6
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Biodiversity
The DNA barcode
at the service of marine biodiversity
Echinogammarus ischnus and part of its DNA code Echinogammarus ischnus and part of its DNA code (4 colours corresponding to the 4 nucleobases found in DNA)

A. Radulovici

The oceans provide us with food, raw materials and medicines; they also serve as transportation channels and arenas for outdoor activities. However, they are threatened by overfishing, habitat degradation, pollution and climate change, factors that contribute to the extinction of a number of species. We have to protect marine biodiversity to ensure our survival and prosperity. But before we can do so, we need to know what inhabits the oceans.

Traditionally, species were identified on the basis of their morphology (in other words, their appearance and physical characteristics). But using a new method, DNA barcoding, we can now identify species by means of their genetic characteristics. Just as products sold in supermarkets are identified by barcodes, living species can be identified by a tiny, very specific part of their DNA that differs from one species to the next. These DNA barcodes make it possible to identify organisms quickly, easily and cheaply.

Crustaceans

Crustaceans are a large group of aquatic organisms and present a great variety of sizes, shapes, lifestyles and dispersal behaviours. Some, like krill, are key forage species for other species and their extinction would have serious consequences for ecosystems. Others, like lobsters, crabs and shrimps, are harvested by industries generating earnings in the billions of dollars.

The DNA barcode will have practical benefits. For instance, it will serve to identify crustacean eggs and larvae in plankton samples taken to assess populations. It will also greatly facilitate analysis of the stomach contents of crustaceans and fish, studied to understand “who eats what”. It will be possible to detect hidden species—like illegally traded protected species, parasites, etc.—in processed seafood. It will result in the discovery of invasive and as-yet-unknown species. In the near future, we will be able to know just how rich and diversified our marine world really is!

The very latest results

A library of DNA sequences is being established for Canada’s three oceans. For Eastern Canada, the first results show, for example, that an invasive amphipod species (Echinogammarus ischnus) has arrived in the St. Lawrence estuary after being found in the Great Lakes and the St. Lawrence River a few years ago. Future studies will be able to show the consequences of this invader on the estuary’s native fauna.

Analyses have also revealed that several of Eastern Canada’s marine crustaceans with a similar morphology in fact have different genetic codes (such species are known as “cryptic” species), which suggests that marine biodiversity has been underestimated.

By combining classic and modern identification methods, the biodiversity field has become more dynamic than ever before, particularly this year, the International Year of Biodiversity. It is now possible to freely access numerous DNA sequence data bases on line. A complete image of our marine world will help us improve predictions and draw up better policies to protect our natural resources for future generations.

For more information on this topic:

The Barcode of Life Data System (PDF)
Molecular Ecology Notes 7: 355–364 (http://www.barcodinglife.org)


Adriana Radulovici, doctoral student, UQAR
Under the direction of France Dufresne, UQAR, and Bernard Sainte-Marie, DFO