February 28, 2003
by Bridget Bailey, News Service intern
Gavin Naylor studies the relationship between sharks and parasites in hopes
of learning how viruses are spread. Photo by Bob
Gavin Naylor isn't afraid to venture into shark-infested waters. In fact,
he's been navigating the habitats of these generally fast-swimming,
sharp-toothed fish for 18 years, and has returned home unscathed each time.
He has trekked to exotic locations in Australia, Sulawesi, Mexico and India
to examine sharks that have been caught by native fishermen or ones sold to
Naylor, associate professor of zoology and genetics, readily admits it's not
really sharks that he's interested in. His life's work has been all about
Naylor and a group of researchers from the University of Connecticut are
collecting information about parasite diversity in sharks and rays, to find
out if sharks and their parasites co-evolved.
Naylor said his research could provide the science world with information
about how epidemics are spread.
"A lot of epidemics caused by viruses can be traced to host-switching
events," Naylor said. "The virus will leave one host, jump to another and
then spread like wild fire through the population. Many flu epidemics seem
to start this way."
Naylor said if scientists can understand how easy it is for parasites to
"switch hosts" (move from one host species to another) and if they can
understand the conditions that favor host switching, it might shed some
light on how parasitic host switching causes disease.
Sharks are the perfect fit for this approach because they possess excellent
fossil records, and have a high rate of diversity with more than 380
different living species.
Naylor said that the scores of shark teeth allow biologists to trace sharks'
evolutionary patterns. Biologists believe the huge variety of shark
adaptations and variations may be linked with their parasites.
Through DNA sequencing methods, researchers determine if and how sharks are
related to one another. That's the principle of an "evolutionary tree."
"The best way to study evolution is to take a diverse group and reconstruct
its evolutionary tree," Naylor said.
DNA samples are taken from living sharks to estimate their place on the
evolutionary tree. Fossil teeth indicate when various types of sharks first
"Taken together, these data provide us with a reasonable estimate of both
the sequence and the timing of events that gave rise to the diversity of
living sharks," Naylor said.
This information tells researchers which groups of sharks are most closely
related, which of their traits arose independently and which species need to
be compared in order to understand changes in development.
"If you want to understand how birds acquired their wings, you wouldn't
contrast their development against worms. You contrast them with the closest
relative to birds that did not have wings," he added.
Naylor said the primary goal of the study is to discover new species of
sharks and parasites -- only 10 percent of all parasitic life is known to
man -- and compare the evolutionary patterns of the two.
"It will give us a sense of how specifically tied a pathogen is to its
host," Naylor said. Basically, it will tell the research team how "faithful"
parasites are to their host species of shark.
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