Long-term estrogen exposure of whitefish Coregonus lavaretus induces intersex but not Lake Thun-typical gonad malformations

Abstract

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 17β-estradiol (E2). Fish were fed from first-feeding until 3 yr of age at a daily rate of 0 (control), 0.5 or 50 µg 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. KEY WORDS: Estrogen · Whitefish · Coregous lavaretus · Gonad morphology · Sex differentiation · Intersex · Vitellogenin · Endocrine disruption Resale or republication not permitted without written consent of the publisherDis Aquat Org 84: [43][44][45][46][47][48][49][50][51][52][53][54][55][56] 2009 drinking water for ~400 000 inhabitants of the area, a possible impact of environmental pollution is of particular public concern. In addition, whitefish is a frequently eaten fish and chemical contamination could therefore pose a risk to consumers. Relevant to human health and the health and development of the coregonid populations, it is thus important to clarify the causes of the gonad alterations.Variations in gonad morphology of fish have been reported in a number of studies worldwide (Kinnison et al. 2000, Blazer 2002, Mikaelian et al. 2002. In fact, the morphology and differentiation of the gonads of fish are known to be susceptible to a variety of environmental factors such as temperature (Patino et al. 1996, Baroiller et al. 1999, parasites (Wiklund et al. 1996, Jobling & Tyler 2003 and chemical substances (Kime 1995, Jobling et al. 1998. One environmental condition that has repeatedly been found to cause gonad alterations in fish is exposure to endocrine-disrupting compounds (EDCs) (Segner et al. 2003, Matozzo et al. 2007). Among the endocrine-active substances, chemicals that act as estrogen-receptor ligands and activate estrogen signaling pathways have received the mos...

Macroscopic gonadal deviations and intersex in developing whitefish Coregonus lavaretus

“…One of the best documented examples is the association between VTG levels and intersex manifestation in wild roach in UK rivers (Jobling et al 1998). For whitefish, we could demonstrate such an association in a laboratory study (Kipfer et al 2009), where fish were fed a daily ratio of estradiol (E2) until they were 3 yr old. The E2 administration resulted in an immediate dose-dependent increase of VTG mRNA concentrations in males (and the values stayed at those levels over a 3 yr period) and a dose-dependent frequency of intersex fish.…”

“…Further, VTG mRNA concentrations of males were 3 to 5 orders of magnitude lower than VTG concentration of females, as would be expected for a nonexposure situation. Finally, the mRNA VTG levels of the males from the experimental groups correspond with mRNA concentrations of VTG found in control males reared in tap water (median = 0.1 copies 1000 -1 copies of 18s-RNA; Kipfer et al 2009). This tap water control group was part of a long-term (17β-E2) exposure experiment and males from that group showed an intersex prevalence of 1%.…”

“…Elevated VTG levels in males indicate the presence of these substances in the environment of the fish. Relative quantification of the VTG mRNA gene expression was performed by means of a 2-step realtime RT-PCR, described in detail in Kipfer et al (2009). In brief, total RNA was extracted from liver tissue using Trizol Reagent (Invitrogen), resuspended in RNA storage solution (Invitrogen) and treated with DNase (Ambion).…”

Atrazine disrupts gonadal development in a live-bearing lizard

“…For example, indistinct medulla and cortex, presence of medullary cords and absence of lacunae are all features observed during early ovarian differentiation of other reptilian species, 52,60,61 including the congeneric species N. ocellatus. 52,60,61 Retarded ovarian development has also been reported in the fish Coregonus lavaretus exposed to estradiol during gonad development 62 and in Wistar rats exposed to ethynylestradiol in utero. 63 Similarly, exposure to estrogenic EDCs prevents follicle nest breakdown, thus delaying follicular maturation, and results in the formation of POF in laboratory rodents.…”

Ovarian alterations in wild northern pike Esox lucius females

“…Nath & Kumar 1990, Crump & Trudeau 2009, Segner 2011 or with sex reversal resulting from hormone therapies (e.g. Kipfer et al 2009 (and intersex) gonad tissues (Jobling et al 1998, van Aerle et al 2001, Noaksson et al 2001, Kavanagh et al 2004, Hanson 2009). Hermaphroditic histological changes in the ovaries have also been reported in northern pike (Dominguez et al 1989, Vine et al 2005.…”