Unlocking the Mystery of Sick Sea Lions

ST. PETERSBURG, Fla. (Nov. 3, 2009) - Californians regard their sea lions much the same way Floridians do manatees and those along the Eastern Seaboard regard dolphins - a sentinel species whose health and survival are watched closely as an indicator of both natural and man-made trouble in coastal waters.


Now University of South Florida Postdoctoral Fellow Eric Montie, has produced a powerful new tool to help determine how chemical toxins and pollutants may impact the sea lion by creating the first MRI map of a sea lion's brain. The approach goes a step further by using a technique called "volumetric neuroimaging" - a way to measure the volumes of different parts of the brain from MR images. That approach has been done with humans, but Montie believes the technique is now a first in wildlife. The project was featured on the cover of the October issue of The Anatomical Record.


According to Montie, the California sea lion has been the focus of sensory, communication, cognition, and neurological disease studies in marine mammals before, but until now, researchers lacked a noninvasive approach that they could apply to live animals in order to better understand sea lion brain morphology.


"The study is a milestone in neuroimaging of aquatic mammals. But, we have much broader objectives - we want to use this atlas to understand whether or not man-made pollutants and red tide toxins can interact and affect the sea lion brain," Montie said.


Montie leads a team of fellow scientists at The Marine Mammal Center in Sausalito, Calif.; the Massachusetts Institute of Technology; Eckerd College, Galbraith Marine Science Center, St. Petersburg; the University of Wisconsin School of Veterinary Medicine; and the California Pacific Medical Center at the University of California, San Francisco.


The project is funded by the National Oceanic and Atmospheric Administration's Oceans and Human Health Initiative.


The project is integral with other studies Montie has conducted showing the accumulation of PCBs, DDTs and fire-retardants in the brains of dolphins.


In the wild, California sea lions can be exposed to domoic acid, a marine neurotoxin produced by algal blooms in the Pacific Ocean. Domoic acid has been tagged as the culprit in the deaths of hundreds of sea lions each year.


The toxin causes brain damage that makes sea lions more aggressive, disoriented, and interferes with their ability to navigate. Montie and colleagues are using the MRI map to better understand how the marine toxin affects the brain, specifically, a brain structure called the hippocampus.


PCBs and flame retardants – man-made chemicals found in the oceans and also suspected of impacting sea lions – are known to affect the development of the hippocampus in rats.


"It's possible that developmental exposure to these pollutants may make sea lions more susceptible to domoic acid," Montie said.


"These changes may be subtle and you need to know what the normal brain looks like before you can understand how environmental factors may interfere with its structure," he said. "That's why this MRI atlas and volumetric approaches are so important."


The University of South Florida System is one of the nation's top 63 public research universities and one of 39 community-engaged, four-year public universities as designated by the Carnegie Foundation for the Advancement of Teaching. USF was awarded $380.4 million in research contracts and grants in FY 2008/2009. The system offers 232 degree programs at the undergraduate, graduate, specialist and doctoral levels, including the doctor of medicine. It has a $1.8 billion annual budget, an annual economic impact of $3.2 billion, and serves more than 47,000 students on institutions/campuses in Tampa, St. Petersburg, Sarasota-Manatee and Lakeland. USF is a member of the Big East Athletic Conference.