Molecular analysis of the effect of stressors on oysters

Oysters are an ecologically and economically important marine species that contributed over AU$94 million (edible oysters only) directly to the Australian economy in 2012-13. During their life-time, cultivated and wild oysters are exposed to a variety of environmental stressors, including salinity and temperature fluctuations, pollution and pathogens in their natural habitat. These stressors are quite likely to act synergistically and can be exacerbated by anthropogenic and climate influences (e.g. CO2, extreme weather events). They also have the potential to weaken the oysters, causing them to succumb to disease or predation pressures. In an aquaculture environment, this could impact on the productivity and profitability of the industry. To maintain and potentially improve the health and resilience of oysters, knowledge needs to be gained regarding not only the physiological but also molecular responses to stress. Therefore, this study was carried out on Sydney rock oysters (Saccostrea glomerata) to examine the genes actively expressed in stressed and non-stressed oysters and to determine the molecular response of S. glomerata to a range of environmental stressors. S. glomerata were chosen as they are commercially grown in estuaries throughout New South Wales (NSW) to as far up as Harvey Bay in Queensland, as well as in Western Australia’s Albany, with an economic value of over AU$31 million in 2013-14 in NSW alone. For this study, wild S. glomerata were challenged with sub-optimal levels of a) CO2 and temperature, b) copper, c) salinity and temperature and d) polycyclic aromatic hydrocarbons (PAHs) to mimic oil contamination. Collected tissues (haemolymph, gill, mantle, adductor muscle, digestive system and gonad) of all experimental animals were used to generate a S. glomerata transcriptome. Close examination of the transcriptome revealed a wide range of transcripts putatively involved in innate immunity, with some of them (e.g. Toll-like receptor signalling pathways, apoptosis) appearing to be largely conserved between mammals and invertebrates (e.g. oysters). Furthermore, a few selected transcripts were observed to be expressed in specific tissues (e.g. only in the haemolymph).Submitted in the fulfilment of the requirements of the degree of Doctor of Philosphy, University of the Sunshine Coast, 201