Acronym NA
Category
Fisheries
Title Inventory, dynamics and impact of the trematodes parasites in bivalves with high economic importance Programme International Cooperation
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source Other Coordinator Rosa Freitas Coordinator email NA
Coordinator institution
CESAM - Centre for Environmental and Marine Studies (Portugal)
Institutions involved
NA - University of Bordeaux 1 (France) ,
Start year 2012 End year 2014 Funding (€) € 5,000 Website https://ria.ua.pt/handle/10773/26155 Summary Among population dynamics drivers, parasitism is significant but often neglected. Beyond inventory of the various parasites, it is urgent to understand the susceptibility of hosts, namely bivalves, to infection, and to investigate the interaction among parasites and other environmental conditions. In this way, the present study aimed to characterize and quantify the trematode macroparasites, the most abundant and prevalent in coastal waters, infecting Cerastoderma edule and Donax trunculus, which are among the most ecologically important and economically explored bivalve species in Portugal and France. The first step was to study bivalve population dynamics, evaluating the relationship between temperature and recruitment timing and the reciprocal effects of recruitment on adult biomass. For this, a large database spanning 17 years of monthly observations of a cockle population inhabiting a national protected area (Banc d’Arguin, Arcachon, France) was analysed. Long-term observations showed that the sustainability of a cockle population is recruitment-success dependent. In cockles, recruitment success showed to be partly, but not only, dependent on temperature. Hence, the sustainability of a cohort could be set earlier, i.e. by processes happening before recruitment. Following this clue, the role of parasitism on the bivalve host population dynamics was explored. Firstly, due to high pathogenicity for bivalves, special attention was given to the parasites Bucephalus minimus and Bacciger bacciger which use C. edule and D. trunculus, respectively, as first intermediate hosts (where their sporocysts parasitic stage develops). Classic methods of host dissection for parasites identification were combined with transcriptomic and biochemistry approaches. Results revealed some essential aspects of a host-parasite dynamics, such as the positive relationship between first host size and parasite prevalence, the statement of temperature as an important driver of parasite prevalence in its first intermediate host, and the higher parasite prevalence (as sporocysts) leading to higher metacercariae abundance of other species. For both case studies (C. edule collected in Arcachon, France and D. trunculus collected in Faro, Portugal), it was demonstrated that the parasite has a negative effect on its first intermediate host by increasing the metabolic rate, decreasing the energy reserves and inhibiting the antioxidant enzymes activity, which in some months led to cellular damages. Then, the study focused on metacercariae infection in its bivalve second intermediate host, a relationship that is usually reported as less deleterious. However, when certain abundance thresholds are exceeded, metacercariae are able to disrupt some of the bivalve basic functions. The spatio-temporal variability of the structure of trematode community infecting C. edule at the scale of the Ria de Aveiro (Portugal) was characterized and showed to be influenced by multiple abiotic factors and target host population density. Thus, the role of bivalve population density on individual infection rate was further explored in a field long-term monitoring and field experiment study. It was demonstrated that the encounter-dilution effect can be applied also to natural bivalve populations. Lastly, the susceptibility of bivalves to parasites infection when challenged by climate change related factors (salinity, temperature and pH) and contamination (Arsenic) was experimentally assessed. Main results showed that hosts exposure to stressful conditions related to global change scenarios can modify the parasite infection success and induced host biochemical response alterations. The findings presented in this thesis improved the knowledge on the effects of different constraints on bivalves, highlighting the crucial role of parasitism. If applied, these new insights can promote the sustainable management of bivalves, such an important marine resource, with greater production and economic potential.
Keywords
Bivalve;
Mollusc;
Animal welfare;
Parasite;
Biology;
Shellfish;
Clam;
Marine Region
38
Portuguese Waters (27.IXa,27.IXb)
15
Bay of Biscay Central (27.VIIIb)
2
Marine Region Map
