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Title: Marine invertebrate sperm as an indicator of metal toxicity
Author: Lockyer, Antony
ISNI:       0000 0004 8500 1917
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Elevated concentrations of metals have been reported in the marine environment globally where they have the capacity to be toxic to marine organisms. Of concern are the fertilisation and early development of marine invertebrates which are vulnerable to metal toxicity. Scientific and technological advances have enabled the development of numerous rapid, accurate, and semi-autonomous methods for the assessment of sperm. Consequently, sperm parameters are being recommended as rapid alternative endpoints to fertilisation success. For these parameters to be used as endpoints in water quality guideline derivation, ecological relevance needs to be demonstrated via a proven adverse outcome pathway (AOP). This research assessed the effects of metals (Cu, Zn, Cd and Pb) to fertilisation success in the marine invertebrate Galeolaria caepitosa and found that the primary cause of toxicity was through effects on sperm. When the impact of a toxicant is to sperm, current protocols for fertilisation assays could underestimate toxicity. This study found up to three-fold differences in toxicity estimates at sperm densities that all yield >80% fertilisation in controls. More appropriate toxicity estimates would be achieved by assessing toxicity using low sperm densities, for example, those which achieve only 50% fertilisation success. Alternatively, sperm endpoints could be used to provide sensitive (and conservative) toxicity estimates, provided an AOP has been established. For Cu, effects on sperm motility (%) could account for the effects of metals on fertilisation success, and thus can be used as an indicator of Cu toxicity. For Zn, effects on the ability for sperm to undergo the acrosome reaction can be used as a rapid indicator of effects to fertilisation success. However, For Cd and Pb, effects on fertilisation could not be appropriately represented by any of the sperm endpoints tested here. This research highlights the importance of understanding the mechanism of toxicity to fertilisation success and provides recommendations for future ecotoxicological assessments.
Supervisor: Styan, C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available