David Braun
National Geographic News
May 9, 2001
A study of frogs that could yield benefits for both conservation
and human health has received the 7,000th grant awarded by
the National Geographic Society's Committee for Research and
Exploration.
The recipient of the grant is Tyrone B. Hayes, 33, an associate
professor in the department of integrative biology at the
University of California, Berkeley.
Funding for Hayes' research was approved by the National
Geographic committee at a recent meeting in Peru, where committee
members visited several scientists in the field who are also
being supported by the Society.
Hayes' project brings to 7,000 the total number of grants
that the Committee for Research and Exploration has awarded
since it was established more than a century ago. The long
list of grantees and their work includes some of the most
distinguished names in research and exploration and a number
of milestones in science and discovery (see sidebar).
Hayes will use the grant to further his study of the genus
Hyperolius, a reed frog that is common in Africa. His work
focuses on frog hormones, many of which are very similar to
human hormones.
As part of the research, Hayes will conduct studies of the
African reed frog this year in Ethiopia and Uganda. Several
members of the Hyperolius genus change color permanently when
they reach maturity and are able to reproduce, and in some
species the males' coloring is different from that of females.
Both traits are rare in frogs, and determining the cause may
provide insight as well into characteristics of other species.
"Tyrone is an amazing young scholar [with] extraordinary
synthetic abilities," said Raymond B. Huey, professor
in the zoology department at the University of Washington.
"This is a bold project, which requires a synthesis of
very different fields—hormones, embryology and pollution.
And he is tackling this not in the lab, but in the bush in
Africa."
Probing Color Change
Hayes' research team will observe, count and gather reed
frogs in the field to study whether differences in color patterns
are genetically controlled and whether hormones alter color
patterns.
Exploring the influence of genetics and hormones on color
pattern variation in males within a species requires studying
different populations of a single species. Hayes' research
team wants to determine whether males with different color
patterns exhibit different behaviors.
The researchers hope to learn the ecological and evolutionary
reasons for the sexual color differences in the species.
"In understanding hormonal mechanisms and potential
adaptive advantages within populations, we will gain insight
into the mechanisms leading to differences between populations
and the differences between species," said Hayes.
Hayes' research has implications for conservation and public
health. According to an article in the May 2001 National Geographic
magazine, a serious decline in the population of frogs signals
something is amiss in the natural world.
Many hormones found in frogs are similar, and in some cases
identical, to human hormones. Chemicals that affect hormonal
development in frogs could have implications for human health.
Hormones in frogs orchestrate their development from egg
to tadpole, and the metamorphosis from tadpole to adult frog.
During metamorphosis, frogs are very sensitive to changes
in their environment, including chemicals in the water or
their food supply.
Possible Bio-Sensor?
Hayes said the extraordinary sensitivity of the frogs' skin
means that one day it may be possible to use these amphibians
as a cost-effective way to detect the presence of chemicals
in water used by humans.
"Many chemicals mimic hormones in their effect on frogs,"
Hayes said. "We've found that tadpoles show developmental
changes in water that has contaminants fifty times lower than
what's allowed to be in drinking water in the United States.
That's an indication of the ability of frogs to detect pollution
in the environment. If chemicals in such low concentrations
can impact amphibians, it may be an indication that mammals
also may be affected."
"This is exciting research," said Huey. "Tyrone
Hayes has discovered that the color of adult frogs is altered
by exposure to low levels of toxicants in water.
"But what is so brilliant is Tyrone's realization that
this seemingly simple observation can be applied in developing
countries as an almost cost-free 'biossay' of pollution,"
Huey added. "Merely raise some frogs in local water,
look at the resultant adults, and one immediately knows whether
certain pollutants might be a concern."
Copyright National Geographic
Reprinted from http://news.nationalgeographic.com/news/2001/05/0509_grantmilestone.html
