Froglog52

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Mantella madagascariensis by Tim Halliday

ISSN 1026-0269

FROGLOG Newsletter of the Declining Amphibian Populations Task Force August 2002, Number 52. Northern redlegged frogs and endocrine disrupting compounds (EDCs). By James B. Bettaso, Hartwell H. Welsh, Jr. & Brent D. Palmer Endocrine disrupting compounds (EDCs) have been defined as an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub) populations (Damstra et al. 2002). Many human-made compounds have been implicated in disrupting endocrine function in wildlife worldwide, including agricultural and industrial chemicals. EDCs may affect amphibians at several life stages. Their complex life cycles involve aquatic and terrestrial phases, each of which may be exposed to EDCs via these different environments. Amphibians may also be exposed to increase levels of EDCs in their prey as these compounds pass up the food chain in the process of biomagnification. Amphibians as sentinel taxa for detecting EDCs are a logical approach to assessing ecosystem status with regards to these stressor compounds (Palmer et al. 1998). The definition of a biomarker is a chemical, biochemical, physiological, or behavioral endpoint that can be used to assess exposure or effect by an environmental stressor (Kendall et al. 1998). The use of the biomarker vitellogenin (VTG) has been extensively employed in fisheries research on the effects of estrogenmimicking compounds (Sumpter & Jobling 1995, Matthiessen 1998). Vitellogenin is a protein produced by female oviparous vertebrates under normal estrogen regulation and not normally produced by males or subadult animals. Polyclonal antibodies that recognize amphibian

VTG have been developed (Palmer & Palmer 1995, Selcer et al. 2001) in the form of an enzyme-linked immunosorbent assay (ELISA) test. We used these bioassays to test for the production of VTG in wild populations of northern red-legged frogs (Rana aurora aurora) in coastal, northwestern California, USA, seeking evidence of exposure to estrogenmimicking compounds. In 1999 and 2000, wild populations of R. a. aurora were surveyed for endocrine disruption by plasma analysis for VTG. ELISA analysis in 1999 indicated 67% (4 of 6) of the populations tested contained male red-legged frogs producing VTG. In 2000, ELISA analysis showed that 56% (5 of 9) of the populations tested exhibited male and subadult redlegged frogs producing VTG. For the two years of this study, 9 of the 13 study sites tested (69%) had animals producing VTG. This is the first evidence that one or more exogenous sources of estrogen or estrogen mimics are present in the environment of the north coast of California. The recent work on the pesticide atrazine inducing hermaphroditism in African clawed frogs in the laboratory argues for additional work in wild populations of amphibians (Hayes et al. 2002). Laboratory studies on African clawed frogs has shown that a variety of pesticides, industrial chemicals and pharmaceuticals can induce estrogenic effects (Palmer and Palmer 1995; Palmer et al. 1998; Selcer et al. 2001). With the production of VTG in males and subadults in wild populations of R. a. aurora, further research into possible estrogenic effects in these amphibians could prove fruitful. This work is the first to our knowledge to document endocrine disruption in a wild population of amphibians. The potential for endocrine disrupting chemicals to produce both subtle (such as VTG induction) and pronounced (such as

sex reversal) harmful effects may lead to amphibian population declines. This research was funded in part by a DAPTF seed grant in 1998 for equipment necessary to collect plasma samples. This is the first report of results derived from that support. This is a part of JBB’s research for a Master’s of Science in Wildlife at Humboldt State University in collaboration with HHW at Redwoods Sciences Lab and BDP at the University of Kentucky. 1,3 Contact: James B. Bettaso , 1 Hartwell H. Welsh, Jr. & Brent D. 2 Palmer (1) Redwood Sciences Lab, Pacific Southwest Research Station, US Forest Service, 1700 Bayview Dr., Arcata, CA 95521, USA. (2) Department of Biology, University of Kentucky, Lexington, KY 40506, USA. (3) jbettaso@fs.fed.us. Literature Cited Damstra, T., Barlow, S., Bergman, A., Kavlock, R. & Van Der Kraak, G. (2002) State of the Science on Endocrine Disruptors. International Program on Chemical Safety. World Health Organization: http://ehp.niehs.nih.gov/who Hayes, T.B., Collins A. et al. (2002) Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses. Proc. Natl. Acad. Sci. USA 99(8): 5476-5480. Kendall, R., Dickerson, R. et al. (Eds.) (1998) Principles and processes for evaluating endocrine disruption in wildlife. SETAC technical publications series. Matthiessen, P. (1998) In: Principles and processes for evaluating endocrine disruption in wildlife. Kendall, R., Dickerson, R. et al. (Eds.). SETAC technical publications series. Palmer, B.D. & Palmer, S.K. (1995) Vitellogenin induction by xenobiotic estrogens in the red-eared turtle and African clawed frog. Environmental Health Perspectives 103(Suppl 4): 19-25. Palmer, B.D., Huth, L.K., Pieto, D.L. & Selcer, K. W. (1998) Vitellogenin as a biomarker for xenobiotic estrogens in an amphibian model system. Environmental Toxicology and Chemistry 17(1): 30-36. Selcer, K.W., Nagaraja, S. et al. (2001) Vitellogenin as a biomarker for estrogenic

The World Conservation Union (IUCN)/Species Survival Commission (SSC) The Open University " The World Congress of Herpetology " Harvard University


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