Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.583497
Title: Molecular genetic biomarkers of reproductive fitness in earthworms
Author: Ricketts, Huw John
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2004
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Abstract:
When ecotoxicologists assess the environmental impact of pollution they must pose a fundamental question. That is, is the toxicological data produced from any experiment ecologically relevant It has long been thought that a measure of survival of any organism is not sufficient to predict potential population effects. A more sensitive method is the measurement of sub-lethal endpoints, such as growth and reproduction. However, measurement of these parameters may not give an 'early warning' of the impact of complex pollutants within any ecosystem. Therefore, so-called biomarkers have been developed to fill this void. Biomarkers can be used at a number of organisational levels e.g. cellular, protein or DNA, but they all have the sensitivity to act as predictive tools in ecotoxicology and risk assessment. In the past twenty years earthworms have become model organisms in terrestrial ecotoxicology. This is mainly due to the critical role they play within the soil ecosystem in most parts of the world. Therefore the present study utilises three earthworm species (Eisenia fetida, Eisenia andrei and Lumbricus rubellus) to identify, characterise and validate molecular genetic biomarkers of reproduction. To isolate potential reproductive genes a subtractive library was created from the anterior and posterior segments of Lumbricus rubellus. A number of potential biomarker candidate genes were identified, but a putative sperm-specific antigen warranted special attention. The gene fragment of this putative sperm antigen was identified in all three earthworm species used in the study and its potential as a biomarker is discussed. Annetocin has previously been characterised as a member of the mammalian vasopressin/oxytocin superfamily of neuropeptides and has been shown to induce egg-laying behaviours in Eisenia fetida. The annetocin gene was isolated from the three earthworm species and shown to be expressed in the reproductive segments of Eisenia fetida. The expression levels of the annetocin gene were determined in earthworms exposed to metalliferous soils both in laboratory and semi-field exposures using quantitative PCR. A decrease in annetocin gene expression levels correlated with a similar decrease in cocoon production rates of Eisenia fetida after metal exposure. Upon exposure to the mammalian steroid hormones, 17/3-oestradiol and testosterone along with the synthetic oestrogen 17a-ethynylestradiol, annetocin gene expression levels in Eisenia andrei were elevated in some cases, suggesting a role for oestrogens in earthworm reproduction. Eisenia andrei were also exposed to bisphenol A and nonylphenol in artificial soils and annetocin gene expression was determined. Although toxic to Eisenia andrei these two (weakly oestrogenic) compounds did not affect annetocin gene expression. These data strongly suggest that annetocin plays a critical role in earthworm reproduction and that oestrogens may modulate the expression of this gene. The annetocin genomic structure was determined and three oestrogen-responsive elements were identified within the promoter of the gene in Eisenia fetida. What is more, the genomic structure of annetocin conformed to the three exon, two intron model of vasopressin/oxytocin superfamily neuropeptides.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.583497  DOI: Not available
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