Contaminant-induced endocrine and reproductive alterations in reptiles
L. J. Guillette, Jr. and T. Iguchi
Department of Zoology, 223 Bartram Hall, P.O.Box 118525,
University of Florida, Gainesville, FL 32611, USA; Department of Bioenvironmental
Research, Center for Integrative Bioscience, National Institute of Basic
Biology, Okazaki National Research Institutes, 38 Nishigonaka, Myodaiji,
Okazaki 444-8585, Japan
Abstract: Many chemicals introduced into the environment by
humans adversely affect embryonic development and the functioning of
the vertebrate reproductive system. It has been hypothesized that many
developmental alterations are due to the endocrine-disruptive effects
of various environmental contaminants. The endocrine system exhibits
an organizational effect on the developing embryo, altering gene expression
and dosing. Thus, a disruption of the normal hormonal signals can permanently
modify the organization and future functioning of the reproductive and
endocrine system. We have worked extensively with contaminant-exposed
and reference populations of the American alligator (Alligator mississippiensis)
as well as performed a number of experimental studies exposing developing
embryos to various persistent and nonpersistent pesticides. Using this
species, we have described altered steroidogenesis, circulating hormone
levels, and hepatic transformation of androgen and endocrine organ (gonad,
thyroid) morphology in juvenile alligators living in polluted environments.
Given the adverse observations reported to date, we recommend several
important future needs:
1. Further development of "receptor zoos" and other molecular tools
that include key reptiles from various major ecosystems, in addition
to freshwater ecosystems.
2. Global studies extending the current knowledge base on crocodilians
and freshwater turtles to comparable ecosystems on other continents,
such as linked studies examining and extending current molecular to
population level studies in Florida (USA) to tropical and temporate
regions of Africa, Australia, and South America.
3. Further studies of actual exposure, assimilation and excretion
of contaminants by ectothermic vertebrates, especially reptiles that
occupy high levels of the food chain.
*Report from a SCOPE/IUPAC project: Implication of
Endocrine Active Substances for Human and Wildlife (J. Miyamoto and
J.Burger, editors). Other reports are published in this issue,
pp. 1617-2615.
