Browsing by Author "Ruano, Francisco"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- Asynchrony in settlement time between the closely related oysters Crassostrea angulata and C. gigas in Ria Formosa lagoon (Portugal)Publication . Batista, Frederico; G Fonseca, Vera; Ruano, Francisco; Boudry, PierreThe Portuguese oyster Crassostrea angulata and the Pacific oyster Crassostrea gigas are very closely related species originating from Asia that were introduced in Europe. The objectives of the present study were to determine if there is asynchrony in settlement time of C. angulata and C. gigas larvae in an area where both taxa coexist and if hybridization between the two species occurs throughout the breeding season. Oyster collectors were deployed every two weeks during one year in two different sites in Ria Formosa lagoon (Portugal) and the oysters that settled were genotyped with nuclear and mitochondrial markers. Settlement of Crassostrea sp. was observed from April to November 2004 (n = 694), with two distinct periods. In the first period (April), when 19% of the oysters settled, the haplotypes and alleles characteristic of C. gigas were mainly observed. In the following settlement period (July to November), the frequency of haplotypes and alleles of C. gigas decreased over time while those characteristics of C. angulata reached high frequencies by the end of the settlement period. Our results suggest that C. gigas was able to reproduce at lower temperatures than C. angulata in spring. However, the non-significant allelic disequilibrium observed during almost all settlement periods suggests that hybridization is widespread in time. The results obtained in the present study show that there are differences in the reproductive behavior between C. angulata and C. gigas that may limit gene flow between the two species.
- Comparative study of shell shape and muscle scar pigmentation in the closely related cupped oysters Crassostrea angulata, C-gigas and their reciprocal hybridsPublication . Batista, Frederico M.; Ben-Hamadou, Radhouan; Vera G Fonseca; Taris, Nicolas; Ruano, Francisco; Reis-Henriques, Maria A.; Boudry, PierreThe taxonomic status of the cupped oysters Crassostrea angulata and C. gigas has received considerable attention in the last decades. Based on larval shell morphology, experimental hybridization, allozymes and nuclear DNA studies several authors have considered these two taxa as being synonymous. However, mitochondrial data showed clear genetic differences between the two taxa. In addition, microsatellite- based studies and cytogenetic studies have also provided evidence that supports their differentiation. Considerable differences have also been observed at the phenotypic level in terms of growth rate and ecophysiological parameters. In the present study, C. angulata from Sado estuary ( Portugal) and C. gigas from Seudre estuary ( France) were collected and factorial crosses were performed. Juveniles of the different progenies were reared in Ria Formosa ( Portugal) under common conditions to determine if they exhibited differences in shell shape and in pigmentation of the adductor muscle scar. Significant morphometric differences between C. angulata and C. gigas progenies were indicated by univariate and multivariate analyses. Univariate analysis of size- adjusted shell measurements revealed significant differences between the two taxa for shell depth, muscle scar height, and length of ligamental area. Both reciprocal hybrids showed intermediate morphometric characters between parental lines. In addition, significant differences were also observed between C. angulata and C. gigas progenies in terms of pigmentation of adductor muscle scar. C. angulata and both reciprocal hybrid progenies showed highly pigmented adductor muscle scars whereas in C. gigas progeny the pigmentation was lighter. The differences in shell shape and muscle scar pigmentation observed in the present study support the distinction of the two taxa.
- Cytogenetics of Bolinus brandaris and phylogenetic inferences within the Muricidae (Mollusca: Gastropoda)Publication . Leitao, Alexandra; Vasconcelos, Paulo; Ben-Hamadou, Radhouan; Gaspar, Miguel; Barroso, Carlos M.; Ruano, FranciscoThe purple dye murex, Bolinus brandaris (Linnaeus, 1758), is a muricid gastropod common throughout the Mediterranean and along the Moroccan and Portuguese Atlantic coasts. In the present study, we confirmed the diploid chromosome number of 2n = 70 for this species, and established for the first time the karyotype, which comprised 12 metacentric, 15 submetacentric and eight subtelocentric chromosome pairs. To facilitate cytotaxonomic comparisons, we carried out a comparative karyological analysis through multidimensional scaling between B. brandaris and three other 2n = 70 muricid species (Hexaplex trunculus, Ocenebra erinaceus, and Stramonita haemastoma) for which chromosomal measurements have been previously published. The interpretation of the ideograms and the statistical analysis highlighted the closest similarity of B. brandaris and H. trunculus compared to S. haemastoma and O. erinaceus. Indeed, B. brandaris and H. trunculus showed the smallest dissimilarities both for relative length and arm ratio, with O. erinaceus presenting intermediate values, whereas the highest dissimilarities were found between H. trunculus and S. haemastoma for both data. The karyotypes of B. brandaris and H. trunculus (subfamily Muricinae) presented the highest proportions of metacentric chromosomes compared to the other two muricids analysed, suggesting that those karyotypes could be considered primitive within the 2n = 70 Muricidae studied so far. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 185-193.
- Insights on the association between somatic aneuploidy and ostreid herpesvirus 1 detection in the oysters Crassostrea gigas, C. angulata and their F1 hybridsPublication . Batista, Frederico; Lopez-Sanmartin, Monserrat; Boudry, Pierre; Navas, Jose I.; Ruano, Francisco; Renault, Tristan; Fonseca, Vera G.; Leitao, AlexandraCytogenetic abnormalities associated with viral infections, including from viruses of the Herpesvirales order, have been reported in vertebrate species. Ostreid herpesvirus 1 (OsHV-1) has been detected worldwide during mortality outbreaks of the Pacific oyster Crassostrea gigas. On the other hand, a high proportion of aneuploid cells in somatic tissues have been observed in C. gigas. In this study, we analysed the putative association between aneuploidy levels and the detection of OsHV-1 in gills of C. gigas, the Portuguese oyster C. angulata and their F1 hybrids cultured in Ria Formosa (Portugal). OsHV-1 was detected by PCR in 5.4% of the total of oysters analysed (n = 111) namely in 11.1%, 8.0% and 1.7% of C. gigas, C. angulata and F1 hybrid respectively. Sequencing analysis of a viral fragment amplified with the C2/C6 primer pair revealed a high similarity with the OsHV-1 reference type. Moreover, in situ hybridization confirmed the presence of OsHV-1 in gill tissue. Oysters where OsHV-1 was detected had a significantly higher mean percentage of aneuploid cells (25%) than the ones where the virus was not detected (18%). However, the overall low percentage of positive samples contrasted with the high mean percentage of aneuploidy observed, with 50% of the oysters analysed showing a percentage of aneuploid cells between 20% and 30%. We hypothesize that somatic aneuploidy may adversely affect oysters making them more prone to OsHV-1 infection, but the virus is unlikely to be the cause of somatic aneuploidy.
- New insights about the introduction of the Portuguese oyster, Crassostrea angulata, into the North East Atlantic from Asia based on a highly polymorphic mitochondrial regionPublication . Lallias, Delphine; Power, Deborah; Ruano, Francisco; Leitão, Alexandra; Drago, Teresa; King, Jonathan W.; Boudry, Pierre; Batista, FredericoIt is commonly presumed that the Portuguese oyster Crassostrea angulata was introduced into the North East (NE) Atlantic from Asia. The analysis of the nucleotide sequence of a highly polymorphic non-coding mitochondrial region (major noncoding region - MNR) of C. angulata samples collected in Europe (Portugal), Africa (Morocco) and Asia (Shantou and Taiwan) provided new insight into the introduction of this species into the NE Atlantic. Sixty haplotypes and a nucleotide diversity of 0.0077 were observed in 130 analyzed sequences. Higher nucleotide diversity levels were observed in NE Atlantic sites than in Asian sites and significant genetic differentiation was found between the two. Our results suggest that C. angulata might have been introduced to the NE Atlantic by multiple introductory events, though the exact origins remain unknown since none of the analyzed Asian sites seemed to have been a source of introduction. The nucleotide diversity of C. angulata was higher than that previously reported for Pacific oyster C. gigas in Europe and Asia for the same mitochondrial region. The results obtained in the present study suggest that NE Atlantic C. angulata stocks are a unique genetic resource, which highlights the importance of their conservation.
- Occurrence and characterization of pearls from oysters of the genus CrassostreaPublication . Batista, Frederico; Grade, Ana; Power, Deborah; Ruano, Francisco; Harper, Elizabeth M.The occurrence of pearls in the true' oysters, the Ostreioidea, is poorly documented despite being the most produced mollusc species in the world. Oysters of the Crassostrea genus were collected in two different sites in southern Portugal where both Crassostrea angulata and C. gigas are present, namely in: (1) the Ria Formosa lagoon where pearls were not observed (N = 446); and (2) the Guadiana estuary where pearls were found in 12 out of the 798 oysters analysed. The pearls were located mainly at the edge of the right mantle lobe in the inhalant chamber and their maximum length ranged from 0.9 to 5.5 mm. Almost all the pearls had a white-cream colouration with the exception of two pearls that had a black-brown colour. X-ray diffraction analysis of one pearl showed that it was entirely calcitic with no traces of either aragonite or vaterite. The pearls observed were therefore non-nacreous pearls. Scanning electron microscopy (SEM) revealed a diversity of microstructures including prismatic, foliae-like sheets and blocky textures, i.e. highly reminiscent of the host oyster shell microstructures. Parasites (e.g. parasitic copepods, Haplosporidium-like plasmodia) and signs of diseases (e.g. foot disease) were observed in some of the oysters analysed, but they were not associated with the occurrence of pearls. The present work is one of the few studies on the occurrence of natural pearls in true' oysters and to our knowledge the first description of their microstructure by SEM.