- Title
- Study the male reproductive biology of a marine invertebrate Galeolaria caespitosa and investigate its potential as a bio-indicator species of coastal marine pollution
- Creator
- Lv , Yonggang
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The history of marine pollution can be traced back to the very beginning of human civilisation. Nevertheless, this issue did not raise serious concern until a threshold level was reached with devastating consequences for the marine ecosystem. In recent years, bio-indicator species have been gradually embraced as one of the most effective approaches to predict, monitor and assess marine contamination. The statistics acquired from biomonitoring not only facilitate determination of the biological significance of man-made hazardous substances on marine ecosystems but also establish an important foundation for marine wildlife conservation and public health management. The focal species in this PhD project is an Australian native marine invertebrate Galeolaria caespitosa, which is recognised as a potential bio-indicator species for coastal marine pollution and a model organism for use in laboratory toxicity tests, due to a number of remarkable life history characteristics it exhibits. According to a range of recent studies, the gametes of G. caespitosa, particularly its spermatozoa, and the processes of fertilisation, embryogenesis and larval development were susceptible to marine contaminants and could be utilised as sensitive indicators of pollutants in the immediate environment. Nevertheless, the reproductive biology of this species, particular the male reproductive system, has only been superficially described. This knowledge gap has created an opportunity to undertake a comprehensive investigation of reproduction and embryonic development in this species including the sensitivity of these processes to common environmental contaminants. (1) Utilising serial histological sections and electron microscopic techniques, the male reproductive system in G. caespitosa was reconstructed and the general pattern of spermatogenesis was established. This study for the first time established a comprehensive model of male reproductive system in polychaetes, with the function of each compartment being elucidated in detail. In addition, clear similarities were found between the male reproductive system in this simple invertebrate and human beings in terms of the structure and function.(2) As the differentiation of round spermatids in G. caespitosa took place in the germinal fluid without any physical support from nurse cells, spermiogenesis in this species was regarded as a convenient model for studying the underlying mechanisms of this complex differentiation process. Therefore, spermiogenesis was analysed in detail at the ultrastructural level and a preliminary study was performed to reproduce the differentiation of spermatids in vitro. This in vitro study revealed that the regulators of spermiogenesis in G. caespitosa were gender-specific and involved proteinaceous constituents thereby providing a basis for future studies addressing the molecular regulation of this complex differentiation process. (3) Exposure of spermatozoa to low levels of dibutyl phthalate (DBP) led to impaired embryogenesis and developmental abnormalities that adhered to a common pattern featuring asymmetrical division of the blastomeres. This study yielded important information on the mechanisms underlying DBP-induced embryonic arrest and abnormality, highlighting the reproductive toxicity that DBP exhibits towards the gametes of aquatic invertebrates and providing novel insights into the role that sperm centrioles play in early embryogenesis. (4) By examining the adverse effects of common marine pollutants on early embryogenesis, it was clear that the stress response of spermatozoa, which was reflected by defects in the subsequent embryogenesis, could be utilised as a sensitive indicator for detecting certain chemicals, such as bisphenol A, DBP and a range of alkylphenols.
- Subject
- spermatogenesis; embryogenesis; plasticizer; bio-indicator
- Identifier
- http://hdl.handle.net/1959.13/1332731
- Identifier
- uon:26928
- Rights
- Copyright 2016 Yonggang Lv
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT01 | Thesis | 18 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 547 KB | Adobe Acrobat PDF | View Details Download |