CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Deliverables
This work provides means and standard deviation of compositions in fatty acids, sterols and some vitamin data on a large number of samples of phytoplankton species cultivated in different industrial hatcheries and under different cultivation processes. This is of importance because these molecules are essential for bivalve molluscs. These results will allow hatcheries to appreciate:
1) That no errors are in the species and strains cultivated.
2) That their culture conditions do not affect too much the essential nutriment composition.
3) That when compositions are out of standards there is an increasing risk in larval rearing.
Measurements of the same molecules in eggs, D larvae and further developing stages, provide also standard values defining egg quality, normal embryogenesis, normal nutritional relay. These results will allow hatcheries to appreciate:
1) Quality of their conditioning process using the standard values of eggs and D larvae.
2) Quality of their diet for nutritional relay and further larval development.
3) Errors are detected in the species and strains cultivated : some examples show that species cultivated are not the expected species, probably due to contaminations or errors in the culture process. Measurement of sterol composition or fatty acid composition of the cultivated phytoplanktonic species is the best way to identify the species today.
5) Some parameters as nutrient composition, temperature culture, growth rate and growing stage of the culture can modify the algal composition. Control of sterol or fatty acid composition of algae in the local conditions, and comparison to established means allow detection of abnormal algal culture conditions.
6) Composition of algae in essential nutriments during broodstaock conditioning can affect the storage and membrane composition of eggs leading to low performances in D larval yield. This is demonstrated using Skeletonema diet alone. In a same way, nutritional relay can be affected, as well as larval growth when algal diet is not well equilibrated.
7) Quality of eggs can be estimated by their storage in essential nutriments : fatty acids in neutral and polar lipids in quantity and quality, steryl ester composition and quantity. These molecules control a part of the developmental rate because consumption of steryl esters is huge during embryonic development as well as EPA in polar lipids and vitamins B1 and B2 before nutritional relay.
8) Quality of the diet for nutritional relay and further larval development is also essential and can affect larval growth rate and metamorphosis. Moreover, the feeding sequence can be controlled by measuring these parameters in developing larvae, because each algal species has a specific composition labelling the neutral and polar fraction of larvae. One case showed an example of a perturbation of the ingestion process before appearance of mortalities.
Periodic losses in oyster hatcheries are regularly reported in Europe. Current practise in the private shellfish hatcheries takes account of basic research findings about food provision and some Vibrio infections but uncontrolled variables are still damaging the industry, particularly since 1991. Among these uncontrolled variables, herpes-like virus infections seem to play a key role. The observed association between oyster mortality and herpes-like virus infections provides an imperative to determine the extent to which the virus is involved as a causative agent of larval mortalities in different European countries. PCR was used to investigate the presence of herpes-like virus DNA in larval samples belonging to different bivalve species from different geographical origins.
1) Seventeen samples on the 81 analysed (21 %) appeared positive for the detection of viral DNA. Positive samples were observed in 4 hatcheries from 3 European countries (France, Spain and the United Kingdom). For both French hatcheries, 9 and 5 samples respectively, showed positive PCR results. These results confirm previous data indicating that herpes-like viral infections may be observed in commercial hatcheries in France. Positive PCR results have also been obtained for bivalve larval samples originating from Spain and the United Kingdom, 1 and 2 samples respectively. However, analysis must be pursued in order to confirm these results. Some samples originating from Spain and the United Kingdom were thawed when they had been received at the laboratory for PCR analysis. Negative PCR results or detection of bands presenting unexpected sizes on agarose gels may correspond to damaged viral DNA and the number of positive PCR results may be underestimated. Positive samples were observed in all four bivalve species. The detection of herpes-like virus DNA was reported herein for the first time in larval Ruditapes decussatus. In Europe, herpes-like viruses may be found in four bivalve species at the larval stage.
2) The detection of viral DNA is associated in 13 samples (76.5%) with high mortality rates. Herpes-like viruses may be interpreted as one of the causative agents of the reported mortalities. It is well established in the literature that herpes-like viruses infect larval cells and induce mortality . The successful experimental transmission of a herpes-like viral disease has been reported in axenic Crassostrea gigas larvae. After inoculation of the viral suspension, healthy larvae die quickly and cumulative mortalities reach 100 % on the sixth day post infection. Transmission electron microscopy examination reveal the presence of viral particles in inoculated larvae, whilst in control animals neither lesion, nor virus is detected.
3) The differences observed for herpes-like virus DNA detection depending on the PCR primer pairs used indicate that some primer pairs are more adapted for epidemiological surveys than others. Thus, the primer pair C2/C6 seems well adapted for herpes-like virus DNA detection because of processing ease (simple PCR reactions) and great sensitivity. The PCR protocol using the primer pair C2/C6 limits reagent use and reduces contamination in comparison with the nested PCR protocol using A4/A5 and A5/A6 primer pairs. A rapid response can be obtained for herpes-like virus detection. The availability of a sensitive and reliable PCR technique to detect herpes-like virus DNA in less than 24 hours may be useful to manage larval rearing in commercial hatcheries. The detection of viral DNA by PCR in batches presenting mortalities may help to avoid the spread of viral infections among brood stocks.
Pyrolysis mass spectroscopy is a method that allows the fingerprinting of cells with regards to their chemical composition. It is a technique that has been used as part of the identification matrix for microorganisms, but also was shown in this project to have some utility in allowing comparisons to be made between alagal cultures that reflect their nutritional quality. It was shown that different types of algae that were taxinomically not closely related, but were good sources of food for developing oysters had very similar pyrolysis mass spectroscopy profiles.
The technique does require an initial investment in expensive equipment, but thereafter the analytical costs are fairly low. It would therefore be most appropriate for this technology to be accessed from university laboratories or from commercial companies.
Several different types of algae were screened. Experiments showed that it was possible to resolve Isochyrsis, Skeletonema and Tetraselmis using this technique where the fingerprints produced gave clearly different profiles.
Pavalova and Chaetocerus both allowed good growth of oyster larvae, both also had very similar spectograms, which were significantly different to those obtained from algal cultures which were poorer sources of nutrients.
The nature of the technique allowed samples to be rapidly processed thus giving information in a suitable time-frame to inform hatchery operators of the nature of known or unknown algal cultures (i.e. those resulting from natural blooms).
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