Long-term estrogen exposure of whitefish Coregonus lavaretus induces intersex but not Lake Thun-typical gonad malformations.
A high prevalence of gonad morphological variations has been observed in whitefish Coregonus lavaretus from Lake Thun (Switzerland). To clarify the role of endocrine disruption as a possible cause of the gonad alterations, whitefish were reared in a long-term laboratory experiment under exposure to 17 beta-estradiol (E2). Fish were fed from first-feeding until 3 yr of age at a daily rate of 0 (control), 0.5 or 50 microg E2 kg(-1) fish. E2 exposure resulted in a time- and concentration-dependent increase of prevalence and intensity of intersex gonads, i.e. gonads that macroscopically appeared as either testis or ovary but microscopically contained both male and female germ cells. Four types of intersex could be distinguished: Types 1 and 2 were composed of mainly male tissue, with Type 1 containing single oocytes and Type 2 displaying an ovary-like lamellar structure of the tissue. In Type 3, an increased percentage of the tissue was occupied by female germ cells, while in Type 4, the majority of the gonad tissue consisted of female germ cells. Chronic E2 exposure additionally resulted in a concentration-dependent shift of the sex ratio towards females, a reduced condition factor, retarded gonad growth together with delayed maturation of germ cells, and elevated levels of hepatic vitellogenin mRNA. However, Lake Thun-typical alterations of gonad morphology were not induced by chronic E2 exposure. The results provide evidence that estrogen-active compounds unlikely play a role in the etiology of gonad malformations in Lake Thun whitefish.
Centre for Fish and Wildlife Health, University of Bern, Laenggass-Strasse 122, PO Box 8466, 3001 Bern, Switzerland.
S
S
Kipfer
H
H
Segner
M
M
Wenger
T
T
Wahli
D
D
Bernet
D000818:Animals; D012734:Disorders of Sex Development / Q000139:chemically induced* / Q000473:pathology / Q000662:veterinary; D052244:Endocrine Disruptors / Q000737:chemistry / Q000633:toxicity; D004967:Estrogens / Q000633:toxicity*; D005260:Female; D005393:Fish Diseases / Q000139:chemically induced* / Q000453:epidemiology / Q000473:pathology; D005618:Fresh Water / Q000737:chemistry*; D006066:Gonads / Q000002:abnormalities*; D008297:Male; D012487:Salmonidae / Q000002:abnormalities; D013557:Switzerland / Q000453:epidemiology; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D052244:Endocrine Disruptors; D004967:Estrogens; D014874:Water Pollutants, Chemical