AbstractThe blue mussels (Mytilus sp) are an economically important species for European aquaculture, accounting, by weight, for over 50% of the bivalves produced across Europe. Nevertheless, the European mussel production sector is experiencing a continuous decline, with a net decrease in the production of 21% since 1999. A reliable supply of mussel seed has been indicated as one of the
causes of such decline. The establishment of industrial mussel hatchery production could represent one solution to secure a spat supply to the growers, as it may reduce the reliance of the sector to unreliable natural spatfalls. Nevertheless, hatchery-produced seedlings are expensive, thereof, to ensure a cost-effective product, improvements of existing hatchery practices are necessary.
In this thesis, manipulative experimental trials are employed to assess the principal hatchery practices, namely broodstock conditioning (BSC), early larvae rearing and spat nursery. Factors investigated in the different experimental chapters included the temperature profile during BSC and the effect of different microalgae strains for early larvae and juveniles. The various processes were
monitored through allometric, histological and biometric indexes and coupled by lipid profiling techniques, given the ubiquitous role and importance of lipids for embryo survival and energetic turnover in different stages of the mussel life cycle. The novelty of this thesis is the comprehensive approach employed to investigate mussel lipids (the lipidome), combining fatty acid (FA) and lipid
class analysis with liquid chromatography-mass spectrometry (LC-MS) lipidomics.
Through these approaches, I described the gonad lipidome in the testis and ovary and the acclimation responses to different temperature programmes during BSC in broodstock gonad lipidome. Furthermore, the integration of gonad histological analysis with their lipid profiles permitted the identification of candidate lipid markers distinguishing ripe from undeveloped ovaries, such as ceramide phosphoethanolamine (PE-Cer) 40:1 and the saturated ether-linked glycerophosphocholine (PC) O-30:1/P-30:0b (area under the curve, AUC>0.9). The thesis is completed by two chapters dealing with diet feeding trials on mussel larvae and juveniles. These trials indicated the different nutritional requirements between the two life stages, evidencing the accumulation of neutral lipids in larvae and spat subjected to nutritionally efficient diets. Studying lipid molecular species evidenced also significant trends in membrane lipids according to the PUFA composition of the diet. Unveiling the lipidome of mussels highlighted important information on their physiology and nutrition during hatchery procedures, constituting a relevant baseline for the enhancement of mussel hatchery practices. Here I observed how an increase in holding temperature may alter gonad lipidome during maturation, as well as the significant impact of various diets on storage lipid reserves as well
as membrane lipids which may impact larvae and juvenile survival.
|Date of Award||19 Apr 2021|
|Supervisor||Adam Hughes (Supervisor), P D Whitfield (Supervisor) & Mary Doherty (Supervisor)|