UNDER PRESSURE: ASSESSING MULTIPLE STRESS IN ANTHOZOANS. RESPONSES TO POLLUTION, INFECTION, INFLAMMATION, REGENERATION AND TEMPERATURE PLASTICITY

In this PhD thesis have been investigated the innate immunity responses and physiological biomarkers of Anemonia viridis (Anthozoa, Cnidaria) in the context of inflammation caused by multiple factors such as thermal stress, pathogens, pollutant, and injury. A. viridis could represent an excellent animal model for environmental biomonitoring validation of immunological. A battery of biomarkers, at different levels of biological organization, was used to comprehensively investigate the processes in evidence. Immunity and inflammation are the most evolutionarily widespread and conserved defence mechanism in living organisms in response to pathogens and injuries, which is why I focused on methods that specifically aimed to elucidate these aspects. Organisms have always had to deal with adverse environmental circumstances, which has resulted in the evolution of intricate biological systems to prevent or minimise functional dysregulation. Physiological and molecular mechanisms in cnidarians are not entirely clear and responses to thermal stress in literature resulted extremely different even in species that share a similar genetic pool. Marine invertebrates, including anthozoans, can "acclimate" to thermal stress by modifying some components of their cellular metabolism to better cope with high water temperatures in a climate global change scenario. The physiological acclimatization can involve the host organism, as well as symbionts, and can be modulated by protein factors such as heat shock proteins and immune system effectors. Previous studies have indicated a link between the regulation of the activity of antioxidant enzymes and acclimatization from thermal stress in coral reefs. Indeed, environmental stress can induce an increase in the production of reactive oxygen species (ROS) which damage the cnidarian-Symbiodiniaceae mutualism. The cellular response to the formation of oxygen radicals includes many defence mechanisms such as the activation of scavenger enzymes which act in concert to inactivate the radicals responsible for major cell damage. Moreover, evidence indicates that the anthozoan innate immune system is not only involved in the disruption of harmful microorganisms but is also crucial in structuring tissue-associated microbial communities, that are essential components of the cnidarian holobiont and useful to the animal’s health for several functions including metabolism, immune defence, development, and behaviour. The use of the anthozoan as model will make it possible to read the responses to environmental perturbances, to acquire new knowledge on cellular and molecular mechanisms in invertebrate bioindicators which show a high tissue regeneration capacity compared to other evolutionarily more complex organisms, that due to their immunity system have limited regenerative ability. The results IV obtained here highlighted how A. viridis can be validated as a bioindicator following exposure to heavy metals and how these are agents capable of modulating the immune response of the sea anemone. Then, thanks to the study of tentacular regeneration under constitutive conditions and following thermal stress, it was possible to identify and characterize the stages of regeneration at the macroscopic and tissue levels, the cellular components as well as to study the expression of proteins known to be involved in the inflammatory state and regeneration. Providing valuable information to corroborate the whole process, as a biomarker and also allowing to clarify the link between immunity, inflammation and regeneration. With the aim to study the adaptation to extreme environment, the first investigation on Urticinopsis antarctica, Antarctic species, was carried out, in which in addition to tissue and cellular analysis, de novo sequencing of the entire transcriptome was performed. The results can be useful to have information on the health state of our seas and to focus on molecular products of adaptative selection pressure with potential transferability to biotechnological field. The knowledge of the immunological biomarkers involved in acclimatization reactions could be important for developing monitoring programs and coordinated management of the coastline in order to cope also with the emerging environmental challenges.