Background Gonochorist teleosts are teleosts in which individuals develop either as males or as females, and are sexually stable thereafter throughout ontogeny. However, there is a labile period, defined as the time period prior to hatching through juvenile stage before sexual maturation (adulthood), during which gonadal sex differentiation can be influenced by environmental conditions, including exogenous chemical treatments. Usually, during this period, depending on the nature of chemical treatment, gonadal sex can be reversed from one phenotypic sex to another. A number of chemicals, ranging especially from sex steroids (natural and synthetic) to the more recent one, aromatase inhibitors, have been employed for the purpose of sex reversal in different gonochorist teleost species during the labile period. Thus, the labile period requirement for treatment application before adulthood in order to achieve gonadal sex reversal in gonochorist teleost is well founded. Interestingly, however, some degree of gonadal bipotentiality has recently been reported with mixed findings in adults of certain gonochorist teleost species upon treatment with exogenous chemicals, especially aromatase inhibitors. Consequently, it is now widely thought that gonochorist teleost species are amenable to chemical-induced gonadal sex reversal after sexual maturity. Method Here, all studies on chemical-induced gonadal sex reversal in adult gonochorist teleosts were reviewed. Results Data strongly suggest that there are certain gonochorist teleost species in which adults may not be amenable to gonadal sex reversal through 17β-estradiol depletion by aromatase inhibitors and that the generalization of chemical-induced gonadal sex reversal remains to be experimentally determined in adult gonochorist teleost. Conclusion It was concluded that further studies are required for clarification, considering, among others, that population-level effect models of these chemicals on wild fish populations are based on the understanding that environmental sex reversal occurs only during development and not after sexual maturity.
The Nigerian oil and gas industry has undergone significant changes in exploration, production, transportation and processing of crude oil and refined products due to several key reforms in the sector over the years. These reforms have positioned the upstream, midstream and downstream of the petroleum industry for global competitiveness. Despite these feats, the petroleum industry has a long history of giving lukewarm attention to the issues of environmental management, especially in the Niger Delta region where oil operations are prevalent. The unsustainable exploitation of natural resources by the oil and gas industry, and the reactionary approach of third party activities have resulted in the significant degradation of ecological systems, adversely affecting biological diversity and life support functions for local communities. The legal, regulatory and institutional framework in place has proved inefficient for the holistic protection of the environment, economic livelihood and health of people in the region. As we move into the next decade, there is need for all concerned stakeholders in the oil sector to proactively work together to map out a new path to sustainable exploration of natural resources and improve transparency in the management of oil spill to halt and reverse the environmental degradation in the region.
The developmental and reproductive effects of endocrine disruption on humans and wildlife rank among the most threatening of all environmental health concerns. Particularly vulnerable to chemical assaults are the hypothalamic-pituitary-gonadal (HPG) axis and the hypothalamic-pituitary-thyroid (HPT) axis of the endocrine system. While the effects of endocrine disrupting chemicals (EDCs) on the HPG axis have been the subject of intense research efforts, with comprehensive elucidation, a lot remains to be clarified on the effects of EDCs on thyroid functions. For instance, there are no clear-cut biomarkers of exposure and effects of thyroid disrupting chemicals (TDCs) in intact organisms. Consequently, a number of in vitro assays have been developed, and are particularly useful for the identification and mechanistic characterization of potential TDCs considering the increasing number of EDCs that are being released into the environment. However, with the in vitro assays, studies suggest that a plausible major mode of action of TDCs, thyroid hormone receptor (THR) agonist activity, is not environmentally relevant. Here, we reviewed in vitro detection of TDCs activities in wastewater and surface waters. Data strongly suggest that cell lines may be responsible for the less frequent detection of THR agonist activity in wastewater and surface water. It was concluded that the development of reporter gene assays with thyroid hormone function related cell lines, is required.
Background The environmental prevalence of widely prescribed human pharmaceuticals that target key evolutionary conserved biomolecules present across phyla is concerning. Antidepressants, one of the most widely consumed pharmaceuticals globally, have been developed to target biomolecules modulating monoaminergic neurotransmission, thus interfering with the endogenous regulation of multiple key neurophysiological processes. Furthermore, rising prescription and consumption rates of antidepressants caused by the burgeoning incidence of depression is consistent with increasing reports of antidepressant detection in aquatic environments worldwide. Consequently, there are growing concerns that long-term exposure to environmental levels of antidepressants may cause adverse drug target-specific effects on non-target aquatic organisms. While these concerns have resulted in a considerable body of research addressing a range of toxicological endpoints, drug target-specific effects of environmental levels of different classes of antidepressants in non-target aquatic organisms remain to be understood. Interestingly, evidence suggests that molluscs may be more vulnerable to the effects of antidepressants than any other animal phylum, making them invaluable in understanding the effects of antidepressants on wildlife. Here, a protocol for the systematic review of literature to understand drug target-specific effects of environmental levels of different classes of antidepressants on aquatic molluscs is described. The study will provide critical insight needed to understand and characterize effects of antidepressants relevant to regulatory risk assessment decision-making, and/or direct future research efforts. Methods The systematic review will be conducted in line with the guidelines by the Collaboration for Environmental Evidence (CEE). A literature search on Scopus, Web of Science, PubMed, as well as grey literature databases, will be carried out. Using predefined criteria, study selection, critical appraisal and data extraction will be done by multiple reviewers with a web-based evidence synthesis platform. A narrative synthesis of outcomes of selected studies will be presented. The protocol has been registered in the Open Science Framework (OSF) registry with the registration DOI: 10.17605/OSF.IO/P4H8W.
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