TS. Nguyễn Thị Anh Thư
Panulirus ornatus is a lobster species of high commercial value and commonly cultured using wild-caught seedstock in the Asia-Pacific region. The practice of harvesting wild seedstock places enormous pressure on the sustainability of wild fisheries, which can be alleviated through closed life-cycle culture.
The University of Tasmania-Nexus Aquasciences Pty. Ltd. (UNA) has recently succeeded in the development of technologies for commercial-scale closed-life cycle aquaculture production of P. ornatus. However, further gains in productivity will be linked to more robust health monitoring strategies, including a better understanding of the immune responses of lobsters across ontogenesis and against pathogens.
As is the case for other invertebrates, lobsters lack a true adaptive immune system, yet an expanse of emerging studies propose that invertebrate immunity is more complex than once thought. Therefore, this research aimed to enhance our understanding of lobster immunity which is necessary for developing effective disease-control approaches in lobster aquaculture. The primary aims of this study were to identify immune-related genes from the transcriptome of P. ornatus, map the expression of these immune genes across ontogenesis, and investigate aspects of immunological memory following exposure to pathogens. RNA-sequencing was employed to obtain the first comprehensive description of the transcriptome from immune-related tissues of Panulirus ornatus including numerous immune-related genes associated with pathogen recognition receptors, immune signalling pathways, and immune effectors. A range of important immune genes were confirmed to be highly conserved among arthropods. Differential expression of these genes across late larval (phyllosoma) and postlarval (puerulus and juvenile) development in P. ornatus was mapped. The expression patterns identified highlight that the immune system exhibits plasticity and adapts to different stressors including microorganisms, morphological remodelling (moulting and metamorphosis) and habitat changes. This study showed specific immune priming in P. ornatus haemolymph. Plasma from lobsters primed with either V. harveyi or Y. ruckeri significantly inhibited the growth of V. harveyi or Y. ruckeri respectively when compared to other treatments. This was associated with significantly upregulated expression of genes encoding defensin, ALF and TLR4. This study also demonstrated the memory of lobster immunity. In vitro antibacterial activity of P. ornatus haemolymph towards V. harveyi persists after initial priming and is enhanced upon a secondary exposure to the same bacterial strains. The expression of ALFs, HSP and proPO was significantly upregulated in lobsters injected twice when compared to those injected once with inactivated V. harveyi. Histone acetylation was significantly higher in lobsters re-exposed to V. harveyi compared to naïve controls, implicating histone acetylation might be a driver of immune memory.