Approved Abstracts

Interspecies comparison of lysosomal and tissue-level biomarkers of mussels exposed to water accommodated fraction (WAF) of oil and dispersed oil



Author(s): Lekube X; De Konick V; Telleria U; Rodrigo E; Izagirre U; Soto M; Marigómez I;
Presenter: Xabier Lekube

Mussels are one the most common sentinel species used in biomonitoring programs worldwide to assess the health status of coastal and estuarine ecosystems. As far as the North Atlantic Ocean is concerned, 3 Mytilus species occur: Mytilus edulis, Mytilus trossulus and Mytilus galloprovincialis. Classically, the 3 different mussel species were identified on the basis of their external morphology and their geographical locations fixed consequently, showing unmixed distributions among species. But recent genetic methods, have unveiled a more complex scenario showing that not only the 3 species appear intermingled in many places but also that hybridized species can be frequently found. On the other hand, non-indigenous species such as the black-pygmy mussel Xenostrobus securis are alien organisms that may be responsible for important changes in marine communities (including estuaries), displacing or eliminating native species if they become invasive. This species has been identified as an invasive mussel species in different places worldwide, including estuaries of the Atlantic area from Galicia and Bay of Biscay where they could outcompete with M. galloprovincialis. This risk may also occur in colder climate regions such as the Norwegian Sea and the Baltic Sea, where the major mussel species M. edulis and M. trossulus could also be displaced. So, it may happen in an hypothetic scenario that four different mussel species including the invasive one could cohabit altogether and be used as sentinel species in case of an oil spill event. As far as we know, there is no information about whether the exposure to the same pollutants exerts different biological effects on different mussel species or not. In order to shed some light on this issue, mussels of the aforementioned 4 species were acclimatised to the same water salinity and temperature conditions (15°C and 20 psu) and exposed to the water-accommodated fraction (WAF) of crude oil (naphthenic North Atlantic crude oil) at high concentration (WAF 25%) and low concentration WAF plus Finasol OSR52 (Total Oil) dispersant (WAF 5%D) for 7 days. Lysosomal biomarkes based on histochemical approaches (Lipofucsin determination, intracellular accumulation of neutral lipids, Lysosomal Structural Changes and Lysosomal Membrane Stability) together tissue level biomarkers (cell-type composition in digestive gland epithelium, structural changes of digestive alveoli and connective to diverticular ratio) were analysed. WAF of crude oil and oil-dispersant caused tissue level alterations such as increment in basophilic cells of the digestive diverticula after 7 days of exposure in all the Mytilus species. Interestingly, Xenostrobus securis presented the highest volume density of basophilic cell but did not show any changes in the diverticula cell proportions. WAF of crude oil and oil-dispersant caused both membrane destabilization and different alterations in the structure of lysosomes and in the amount of neutral lipid and lipofuscins in all the analyzed mussel species. However, the responses were different among species depending on the exposure time. This study shows that the four different mussel species had different responsiveness to the oil compounds which could be a confounding factor for the environmental health status assessment after an oil spill and oil spill response.

Acknowlegments: This work was funded by EU GRACE Project (Grant Agreement Number 679266)


Keywords: Mussel species; Biological responses; WAF oil

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