Intersex gonads in frogs: understanding the time course of natural development and role of endocrine disruptors.
The paucity of data on sexual development of anuran amphibians has played an important role in the recent controversy over atrazine exposure. Although some studies have demonstrated the presence of abnormal gonads in control treatments, others have not, leading to varying interpretations of the effects of atrazine exposure on sexual development. However, the timing of development varies among anuran amphibians such that, at any snapshot in time, different species may exhibit different stages of sexual differentiation. We examined three species representing each of the differentiation rates (Bufo americanus=retarded rate; Hyla versicolor=basic rate; Rana sphenocephala=accelerated rate), to examine the natural time course of sexual development along with the influence of atrazine exposure. For each species, exposure to atrazine (1, 3, 10, 30 parts per billion), 17-beta-estradiol or control water occurred throughout larval life. Gonad histology was performed at 3-week intervals during the larval period or at a juvenile stage to examine the proportion of males, females, underdeveloped testes, testicular oocytes (TO; testes with 0-30% oocytes), and ovotestes (OVTs; testes with>30% oocytes). Our results illustrate that a phase of intersex gonads (TO or OVT) is normal during R. sphenocephala sexual development, a species representing the accelerated differentiation rate. Further, intersex gonads were found in juvenile stages of B. americanus and H. versicolor, representing retarded and basic rates, respectively, suggesting that a phase of intersex may be common regardless of differentiation rate. Moreover, these data highlight the importance of longitudinal studies rather than snapshots in time.
Storrs-Méndez
Sara I
SI
Division of Biological Sciences, University of Missouri, Columbia, MO, USA. sisk95@mizzou.edu
Semlitsch
Raymond D
RD
D000818:Animals; D001001:Anura / Q000002:abnormalities* / Q000254:growth & development / Q000502:physiology; D001280:Atrazine / Q000494:pharmacology; D002025:Bufonidae / Q000002:abnormalities / Q000254:growth & development / Q000502:physiology; D012734:Disorders of Sex Development / Q000139:chemically induced / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006066:Gonads / Q000002:abnormalities* / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D006540:Herbicides / Q000494:pharmacology; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D008297:Male; D010053:Ovary / Q000002:abnormalities / Q000187:drug effects / Q000254:growth & development; D011898:Ranidae / Q000002:abnormalities / Q000254:growth & development / Q000502:physiology; D012744:Sex Ratio; D013737:Testis / Q000002:abnormalities / Q000187:drug effects / Q000254:growth & development; D013997:Time Factors
D006540:Herbicides; D004958:Estradiol; D001280:Atrazine