Download Wild mussels from Northern Iberian Peninsula are genetically

SYMPOSIUM on Marine Accidental Oil Spills
Wild mussels from Northern Iberian Peninsula are genetically
identified as Mytilus galloprovincialis according to the Glu-5’
DNA marker
Ionan MARIGÓMEZ, Larraitz GARMENDIA, Eider BILBAO, Ibon CANCIO,
Miren P. CAJARAVILLE
Laboratory of Cell Biology & Histology, Department of Zoology & Animal Cell Biology, School of Science & Technology,
University of the Basque Country, PO BOX 644, E-48080 Bilbo, Basque Country, Spain
ABSTRACT
Although the overall consensus sets up that mussels in the Northern Iberian Peninsula
belong to the species Mytilus galloprovincialis, mussels from this geographical area have been
repeatedly reported to as M. edulis, even in various contributions assessing the effects of the
Prestige oil spill. Several morphologically similar taxa (M. edulis, M. galloprovincialis, M.
californianus and M. trossulus) have been reported within the genus Mytilus and, in addition,
where two of these species are in geographical contact, hybridisation may occur (Inoue et al.,
1995). According to previous reports, M. edulis and M. galloprovincialis exhibit either sympatry
or allopatry, with various degrees of hybridisation, over more than 1000 km of Atlantic coastline
in Western Europe (Hilbish et al., 2002; Gilg and Hilbish 2003). The distribution of these species
and their hybrids has been proposed to be governed by abiotic environmental factors
(temperature, tide level and salinity), which evidences that they posses distinct adaptive
capacities (Braby & Somero 2006; Hilbish et al., 1994). Taxonomical identification is therefore
crucial in biomonitoring programmes in order to achieve a correct interpretation of biomarkers
and disease records, as well as to implement integrative genomic and proteomic approaches.
The objective of the present study was the taxonomical identification of mussels used as
sentinels in the monitoring programme carried out to assess the biological effects of the
Prestige oil spill. For this purpose, the region of the non-repetitive domains of the adhesive
protein gene Glu’5 was examined by the polymerase chain reaction, as a species specific
genetic marker, in mussels collected in 22 localities from Portugal to the Basque coast in
October 2004. DNA was extracted from 10 individuals per sampling locality and Me15 and
Me16 primers were used to amplify the above described portion of the Glu’5 gene (Inoue et al.,
1995). M. edulis from Førlandsfjord (Norway) and M. galloprovincialis from Saronikos Gulf
(Greece) were employed as reference controls. With this primer couple an amplicon 180 bp
long would identify an individual as M. edulis, while a fragment 126 bp long would appear in the
case of M. galloprovincialis due to a deletion of 18 amino acids in the corresponding protein
(Inoue and Odo, 1994). Hybrids can be also identified since two bands of 180 bp and 126 bp
would result amplified in hybrid individuals. Presently, one specific single band of 126 bp was
clearly identified in all the samples analysed from Portugal to the Basque coast as well as in
Mediterranean mussels. Mussels from North Sea, on the other hand, presented one 180 bp
band. These results confirm that all the wild mussels from Northern Iberian Peninsula used as
sentinels to assess the biological effects of the Prestige oil spill belong to the species M.
galloprovincialis and therefore differences found during the biomonitoring programme (Orbea et
al., 2006; Marigómez et al., 2006) can not be attributed to the presence of different taxa in
different localities along the study area.
Funded by the Spanish MEC (VEM2003-20082-CO6-01), Basque Government (ETORTEK actions-IMPRES) and
the University of the Basque Country (Grant to Consolidated Research Groups).
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