Abstract
Effects on fish reproduction can result from a variety of toxicity mechanisms first operating at the molecular level. Notably, the presence in the environment of some compounds termed endocrine disrupting chemicals (EDCs) can cause adverse effects on reproduction by interfering with the endocrine system. In some cases, exposure to EDCs leads to the animal feminization and male fish may develop oocytes in testis (intersex condition). Mugilid fish are well suited sentinel organisms to study the effects of reproductive EDCs in the monitoring of estuarine/marine environments. Up-regulation of aromatases and vitellogenins in males and juveniles and the presence of intersex individuals have been described in a wide array of mullet species worldwide. There is a need to develop new molecular markers to identify early feminization responses and intersex condition in fish populations, studying mechanisms that regulate gonad differentiation under exposure to xenoestrogens. Interestingly, an electrophoresis of gonad RNA, shows a strong expression of 5S rRNA in oocytes, indicating the potential of 5S rRNA and its regulating proteins to become useful molecular makers of oocyte presence in testis. Therefore, the use of these oocyte markers to sex and identify intersex mullets could constitute powerful molecular biomarkers to assess xenoestrogenicity in field conditions.
Highlights
Complex contaminant cocktails arrive at estuarine and coastal areas affecting the health of the organisms inhabiting these special ecosystems
We further want to review the functional significance of some novel, 5S rRNA related, molecular markers of intersex condition identified in thicklip grey mullets, Chelon labrosus, from polluted estuaries in the Basque coast
Within the mugilidae family of fish we find worldwide distributed and strategically placed euryhaline species that are very sensitive to exposure to xenoestrogenic compounds, both under natural and laboratory conditions
Summary
Complex contaminant cocktails arrive at estuarine and coastal areas affecting the health of the organisms inhabiting these special ecosystems. Contaminants classified as reproductive EDCs include plasticizers, pesticides, fungicides, surfactants, dioxins, polychlorinated biphenyls, electrical transformers, and pharmaceuticals such as the synthetic estrogen 17α-ethinylestradiol [8]. Male fish with testis containing oocytes (known as intersex condition) have been described in aquatic environments receiving feminizing EDCs or xenoestrogens. Aromatases, belonging to the P450 cytochrome family of proteins, are responsible for the transformation of androgens into estrogens They are key proteins in the control of steroid balance during sexual differentiation, development and reproduction [21,23]. The aim of the present review is to provide an overview describing the potential of the family of mugilids as pollution sentinels This family of teleosts is very well suited for the study of xenoestrogenic endocrine disruption in coastal ecosystems. We further want to review the functional significance of some novel, 5S rRNA related, molecular markers of intersex condition identified in thicklip grey mullets, Chelon labrosus, from polluted estuaries in the Basque coast
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