Scanning DNA Barcodes in Sea Turtles

Little chunks of DNA can act as unique barcodes that enable scientists to identify an organism. This fact, which underpins a scientific technique known as DNA barcoding, is now helping conservationists who want to better understand sea turtles, a threatened group of marine reptiles. Since sea turtles are pelagic (they roam the open ocean and migrate vast distances), they are notoriously challenging study subjects. DNA barcoding of sea turtles offers clues about their diversity and in turn reveals the effects trends such as climate change, habitat destruction, and bycatching are having on them.

To establish a DNA barcode for an organism, scientists examine what is known as its "mitochondrial DNA" (referred to as "mtDNA" for short). The mtDNA of an organism is separate from the rest of its genetic material. It resides inside the mitochondria of an organism, a membrane-enclosed structure that exists in the cells of most animals.

The reason mtDNA works well as a barcode is that it mutates relatively quickly, evolutionarily speaking. This means that mtDNA often varies significantly between species while it remains quite uniform within a species. Essentially, species have evolved over a enough long enough period of time to have collected more variations in their mtDNA. In contrast, individuals of the same species haven't yet accumulated enough mtDNA mutations to differ significantly. So scientists can scan little chunks of mtDNA like barcodes to determine which individuals belong to the same species.

This DNA barcoding technique is now being applied to sea turtles. There are seven species of sea turtles that inhabit the world's oceans. Of those seven species, two are vulnerable, two are endangered, and three are critically endangered. To better protect both individual species and sea turtles as a group, conservationists are keen to gather as much information as possible about their genetic diversity.

This is just what a team of scientists from the American Museum of Natural History, the University of Canberra, and others recently set out to do. The team, led by Eugenia Naro-Maciel of the American Museum of Natural History, analyzed DNA barcodes for the seven sea turtle species:

"This is the first study to document DNA barcodes of all species of sea turtles from around the world. These barcodes can be used to document biological diversity in a standardized fashion and for the conservation of these charismatic and ecologically important marine animals." ~ Eugenia Naro-Maciel, American Museum of Natural History.

The team hopes to use the information they gather about DNA barcodes in sea turtles to create a database of the group's genetic diversity. This database can then be used to monitor the effects of various trends—population dynamics, habitat loss, climate change, disease, and conservation success.

Refs:

NARO-MACIEL, E., REID, B., FITZSIMMONS, N., LE, M., DESALLE, R., & AMATO, G. (2009). DNA barcodes for globally threatened marine turtles: a registry approach to documenting biodiversity Molecular Ecology Resources DOI: 10.1111/j.1755-0998.2009.02747.x

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