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DNA Study Reveals Sea Turtle Lineage, Outlook 

July 15, 2008

The beach is empty, but the deserted stretch was obviously full of activity the night before, as evidenced by turtle crawl tracks zigzagging from the surf to nest sites in the dunes. A joint research effort can now tell biologists which turtles made these tracks.

Loggerhead sea turtles are returning to Georgia’s beaches and so are their offspring and possibly even the next generation of offspring. New research methods developed by researchers at the Applied Conservation Genetics Lab at the University of Georgia are allowing the Department of Natural Resources (DNR) to identify the nesting turtles and their offspring as they return each year.

The research based on DNA samples taken from the turtles’ eggs will help determine the population structure and genetic diversity of loggerheads nesting on the Georgia and Florida coasts.

Genetic diversity is important for adaptation to environmental changes. A certain amount of diversity is necessary for the health, longevity and even survival of a species.

“We’re really excited about the possibilities the new genetic markers and technique have unlocked,” said UGA doctoral student Brian Shamblin. “In partnership with Georgia DNR and cooperators all along the Georgia coast, we’re generating nesting data on a scale unimaginable a few years ago.”

Loggerheads, federally listed as threatened, are Georgia’s primary nesting sea turtle. Research from a DNA pilot study done in 2006 revealed four instances of mother-daughter pairs nesting on the beaches.

“This is an important development because loggerheads do not become sexually mature until sometime between 30 and 35 years of age,” said Mark Dodd, a senior wildlife biologist with the DNR’s Wildlife Resources Division. “If you have a mother-daughter pair nesting on the coast, then you know the mom is at least 60-70 years old and has been reproductively active for 30 years or longer. That is an incredibly long period to be reproductively active.”

DNA samples from the nesting turtles are entered into a database at the UGA genetics laboratory. The genetic research is led by Shamblin, a student in Dr. Joe Nairn’s lab. The database will help researchers determine differences in the current population. The research can also provide details on how long the turtles live, how long they are capable of reproducing, how many times they nest and where they nest (this “site fidelity” is important to gauging the health of the reproductive population).

“For example, if they assume that each female nests four times per season and in truth the females nest five times, then they have far fewer turtles than they thought and the population is much smaller than originally thought,” Dodd said. “These are critical questions to consider when creating a plan for conservation.”

The DNA from the samples is a genetic fingerprint that identifies individuals. “We are able to determine parents and offspring and even ‘cousins’ in each turtle family,” Dodd said.

In the past, researchers relied on tags and transmitters to track specific turtles. But the devices sometimes fail and eventually fall off. DNA research creates a permanent link, a database in which all nesting turtles can be compared.

The new methods are also much easier and more reliable. Although night patrols are still done to collect data, researchers no longer have to catch a female turtle in the act of nesting. Samples can be taken from every nest found. One egg from each nest is collected and as long as the egg is recovered before embryonic contamination, which usually occurs 24 hours after deposition, the mother and lineage can be determined.

“This project is really exciting for us,” said Nairn, an assistant professor in UGA’s Warnell School of Forestry and Natural Resources. “The new genetic techniques and the partnership with Mark Dodd and Georgia DNR enable us to gather information about Georgia’s loggerhead population that we could never obtain with traditional approaches.”


Related Links & Resources:
Reptiles - Turtles, Snakes, Lizards
Loggerhead Sea Turtle Articles
Endangered Reptiles

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