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Environmental pollutants are suspected of causing observed adverse effects on development and reproduction in fish and wildlife. Evidence from the laboratory and field suggests that low levels of synthetic or natural chemicals that modulate or disrupt endocrine processes may be responsible. The aquatic environment is a sink for most all potential endocrine disrupting chemicals (EDCs). From egg fertilization to spawning, fish may be exposed to complex mixtures of steroidogenic chemicals that can interfere with the important activational and organizational processes of their endogenous hormones. One consequence of exposure to EDCs may be disruption of the normal mechanisms of sexual development and differentiation, processes that are highly hormone dependent, with subsequent adverse effects on reproduction. My experiments address the hypothesis that exposure to EDCs during early ontogeny affects sexual development and differentiation in fish manifest at maturation. The dr-R strain of medaka was used as the test organism because of qualities that make it a good laboratory animal model and because it possesses a sex-linked gene for body color allowing visual determination of genetic sex from hatch. Medaka were exposed in ovo by nano-injection to five chemical compounds known or suspected to be hormone mimics or disruptors. Details of the effects resulting from exposure to the synthetic sex steroids ethinyl estradiol (EE 2) and methyl testosterone (MT) provided a reference and established a model for predicting effects of in ovo exposure to chemicals which mimic estrogens and androgens. Effects on medaka exposed to the EDCs, o, p ' -DDE and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and three mixtures of polychlorinated naphthalenes (PCN), which have not been tested for their endocrine disrupting potential, were also investigated. In ovo exposure to 0.5 and 2.5 ng EE 2 /embryo or 0.8 and 8.0 ng MT/embryo affected sexual differentiation by causing sex reversal in males and females, respectively. Sexual development of male and female gonads was also affected at these doses. Most notably, all doses of MT resulted in precocious maturation of male and female medaka. Effects on sexual differentiation of the gonads were not as apparent for o, p ' -DDE, TCDD, and the PCNs as were effects on sexual development. Observed effects of these chemicals included one or more abnormalities: histopathological lesions (e.g., atresia), reduced gonad size, and changes in primary germ cell numbers along with volume of primordial gonads. Results for these chemicals together with other's field and laboratory observations provide further evidence that environmental EDCs may be adversely affecting reproduction and development of wild fishes. These results also support the utility of laboratory studies with the dr-R medaka model within the framework of a weight-of-evidence approach to establish a cause-and-effect relationship between environmental exposure to EDCs and reproductive impairment at the individual and population levels.
Awarded Bookauthority's "Best Aquaculture Books of all Time" A comprehensive resource that covers all the aspects of sex control in aquaculture written by internationally-acclaimed scientists Comprehensive in scope, Sex Control in Aquaculture first explains the concepts and rationale for sex control in aquaculture, which serves different purposes. The most important are: to produce monosex stocks to rear only the fastest-growing sex in some species, to prevent precocious or uncontrolled reproduction in other species and to aid in broodstock management. The application of sex ratio manipulation for population control and invasive species management is also included. Next, this book provides detailed and updated information on the underlying genetic, epigenetic, endocrine and environmental mechanisms responsible for the establishment of the sexes, and explains chromosome set manipulation techniques, hybridization and the latest gene knockout approaches. Furthermore, the book offers detailed protocols and key summarizing information on how sex control is practiced worldwide in 35 major aquaculture species or groups, including fish and crustaceans, and puts the focus on its application in the aquaculture industry. With contributions from an international panel of leading scientists, Sex Control in Aquaculture will appeal to a large audience: aquaculture/fisheries professionals and students, scientists or biologists working with basic aspects of fish/shrimp biology, growth and reproductive endocrinology, genetics, molecular biology, evolutionary biology, and R&D managers and administrators. This text explores sex control technologies and monosex production of commercially-farmed fish and crustacean species that are highly in demand for aquaculture, to improve feed utilization efficiency, reduce energy consumption for reproduction and eliminate a series of problems caused by mixed sex rearing. Thus, this book: Contains contributions from an international panel of leading scientists and professionals in the field Provides comprehensive coverage of both established and new technologies to control sex ratios that are becoming more necessary to increase productivity in aquaculture Includes detailed coverage of the most effective sex control techniques used in the world's most important commercially-farmed species Sex Control in Aquaculture is the comprehensive resource for understanding the biological rationale, scientific principles and real-world practices in this exciting and expanding field.
Some investigators have hypothesized that estrogens and other hormonally active agents found in the environment might be involved in breast cancer increases and sperm count declines in humans as well as deformities and reproductive problems seen in wildlife. This book looks in detail at the science behind the ominous prospect of "estrogen mimics" threatening health and well-being, from the level of ecosystems and populations to individual people and animals. The committee identifies research needs and offers specific recommendations to decision-makers. This authoritative volume: Critically evaluates the literature on hormonally active agents in the environment and identifies known and suspected toxicologic mechanisms and effects of fish, wildlife, and humans. Examines whether and how exposure to hormonally active agents occursâ€"in diet, in pharmaceuticals, from industrial releases into the environmentâ€"and why the debate centers on estrogens. Identifies significant uncertainties, limitations of knowledge, and weaknesses in the scientific literature. The book presents a wealth of information and investigates a wide range of examples across the spectrum of life that might be related to these agents.
This Test Guideline describes an assay that assesses early life-stage effects and potential adverse consequences of putative endocrine disrupting chemicals (e.g. oestrogens, androgens and steroidogenesis inhibitors) on fish sexual development. In ...
Puberty is a unique paradigm for the understanding of gene-environment interaction and developmental programming. Therefore, normal and abnormal pubertal development can be divided and examined in three sections: the role of genetic factors, the role of environmental factors (including nutrition) and therapeutic issues in disorders of puberty. Dealing with all of these sections and framed along current key concepts in pediatric endocrinology, experts share their view on critical issues such as weighting of genetic versus environmental factors or the impact of environmental factors in relation to critical periods in development. Not only showing the consensus and controversial issues in the various areas, each chapter presents lessons for clinical management in an attempt to link basic research, physiology and pathophysiology with the clinical management of pubertal disorders. Puberty from Bench to Clinic bridges up-to-date concepts from animal and human physiology and pathology towards a better understanding and management of pubertal disorders, making it a unique resource for researchers in the field of development and reproduction, clinical scientists and practitioners in neuro-, pediatric and adolescent endocrinology as well as gynecology.
An award-winning scientist, in this urgent, thought-provoking and meticulously researched book, shows how chemicals in the modern environment are changing--and endangering--human sexuality and fertility on the grandest scale.
Timely title assembling the combined knowledge of some of the leading authorities in the field of small fish reproduction - an important topic for risk assessment and registration of chemical, agricultural, and pharmaceutical compounds Provides guidance on the microscopic structure of living tissue and evaluation of the reproductive glands of small laboratory fish Includes state-of-the-art science along with sufficient anatomical and physiological background for understanding and interpreting test results Helps standardize the interpretation of results from aquatic bioassays and field observations, which will also clarify inconsistencies in the current scientific literature Note: CD-ROM/DVD and other supplementary materials are not included as part of eBook file.
The applicability of male plasma vitellogenin as an indicator of reproductive dysfunction in estrogen-treated cunner was investigated. Results suggest that male plasma vitellogenin is not a reliable indicator of reproductive impairment.