Genomics and Transcriptomics of the green mussel explain the durability of its byssus.

Mussels, which occupy important positions in marine ecosystems, attach tightly to underwater substrates using a proteinaceous holdfast known as the byssus, which is tough, durable, and resistant to enzymatic degradation. Although various byssal proteins have been identified, the mechanisms by which it achieves such durability are unknown. Here we report comprehensive identification of genes involved in byssus formation through whole-genome and foot-specific transcriptomic analyses of the green mussel, Perna viridis. Interestingly, proteins encoded by highly expressed genes include proteinase inhibitors and defense proteins, including lysozyme and lectins, in addition to structural proteins and protein modification enzymes that probably catalyze polymerization and insolubilization. This assemblage of structural and protective molecules constitutes a multi-pronged strategy to render the byssus highly resistant to environmental insults.

Evidence for rangewide panmixia despite multiple barriers to dispersal in a marine mussel.

Oceanographic features shape the distributional and genetic patterns of marine species by interrupting or promoting connections among populations. Although general patterns commonly arise, distributional ranges and genetic structure are species-specific and do not always comply with the expected trends. By applying a multimarker genetic approach combined with Lagrangian particle simulations (LPS) we tested the hypothesis that oceanographic features along northeastern Atlantic and Mediterranean shores influence dispersal potential and genetic structure of the intertidal mussel Perna perna. Additionally, by performing environmental niche modelling we assessed the potential and realized niche of P. perna along its entire native distributional range and the environmental factors that best explain its realized distribution. Perna perna showed evidence of panmixia across >4,000 km despite several oceanographic breaking points detected by LPS. This is probably the result of a combination of life history traits, continuous habitat availability and stepping-stone dynamics. Moreover, the niche modelling framework depicted minimum sea surface temperatures (SST) as the major factor shaping P. perna distributional range limits along its native areas. Forthcoming warming SST is expected to further change these limits and allow the species to expand its range polewards though this may be accompanied by retreat from warmer areas.

Crecimiento del mejillón verde Perna viridis (Bivalvia: Mytilidae) bajo sistema de cultivo de fondo en la ensenada de Turpialito, Golfo de Cariaco, Venezuela / Growth and survival of the green mussel P. viridis (Bivalvia: Mytilidae) in bottom culture conditions in Turpialito, Golfo de Cariaco, Venezuela

Mussels represent one of the most important mollusk species for culture activities around the world, and their growth may depend on the culture system used and locality. In this study, we evaluated the growth of Perna viridis in bottom culture to test its performance when using natural food, and to decide its use as a culture species in the Gulf of Cariaco. For this, mussel seeds (35.81±1.41mm in length) were obtained in the locality of Guaca (North coast of Sucre state) and transferred to the Hydrobiological Station of Turpialito, Gulf of Cariaco, Sucre state, Venezuela, where they were planted in “Spanish baskets “ to evaluate their growth between July 2007 and February 2008. Monthly survival was determined and the maximum shell length, dry mass of muscle and remains tissues of the gonad. The environmental parameters (water temperature, salinity, dissolved oxygen, chlorophyll a, total seston and organic fraction), in the cultivation area were determined every 15 days. Monthly measurements were made of proteins, lipids and carbohydrates to seston. During the entire study the mussels showed continued growth, ultimately reaching a maximum length of 78.7±4.43mm. However, the growth rate of the dry mass of somatic (muscle, other tissue) and reproductive tissues showed variability throughout the study, and observed a significant increase by the end of the experiment. The observed variations in the growth rate of the reproductive tissue mass depended on the reserves accumulated and food offered by the environment. The organic seston throughout the experience showed an independence of temperature and chlorophyll a values; this one maintained values above 1mg/L, thus forming the main food resource for mussels. The high content of proteins, lipids and carbohydrates observed in the seston at the end of the study, might be mainly associated with coastal upwelling, which provides a great food contribution of phytoplankton and organic type. The high survival rate (>80%), increase in the length of the shell and the high gonad production, suggests an excellent physiological condition of P. viridis, related to the availability and quality of food particularly the organic type present in the medium. We concluded that the bottom culture can provide an alternative aquaculture production in the Gulf of Cariaco.

Los moluscos representan uno de los grupos más importantes desde el punto de vista económico en la acuicultura marina, debido a los bajos costos de producción y a su alta rentabilidad. En este estudio se planteó probar la hipótesis de un mayor crecimiento de Perna viridis en cultivo de fondo, por un mejor aprovechamiento de alimento presente en el medio, lo cual permitirá descartarla o no como especie de cultivo para el Golfo de Cariaco. En este sentido, se evaluó el crecimiento y la supervivencia del mejillón verde P. viridis en condiciones de cultivo de fondo entre julio 2007 y febrero 2008. Las semillas del mejillón (35.81±1.41mm de longitud) fueron obtenidas en la localidad de Guaca (costa norte del estado Sucre) y trasladadas hasta la Estación Hidrobiológica de Turpialito, golfo de Cariaco, estado Sucre-Venezuela, en donde se sembraron en cestas “españolas”. Mensualmente se determinó supervivencia así como la longitud máxima de la concha, la masa seca del músculo, resto de tejidos y de la gónada. Los parámetros ambientales (temperatura del agua, salinidad, oxígeno disuelto, clorofila a, seston total y su fracción orgánica), en la zona de cultivo se determinaron cada 15 días. Mensualmente se realizaron determinaciones de proteínas, lípidos y carbohidratos al seston. Durante todo el estudio el mejillón mantuvo un crecimiento continuo, alcanzando al final una longitud máxima de 78.7±4.43mm. Sin embargo, la tasa de crecimiento de la masa seca de los tejidos somáticos (músculo, resto de tejido) y reproductivo, mostraron variabilidad a lo largo del estudio, produciéndose al final un incremento significativo en dichos tejidos. Las variaciones observadas en la tasa de crecimiento de la masa del tejido reproductivo, dependió de las reservas acumuladas y del alimento ofertado por el medio ambiente. El seston orgánico durante toda la experiencia mostró una independencia de la temperatura y de la clorofila a manteniendo valores por encima de 1mg/L, constituyendo de esta manera el principal recurso alimenticio para los mejillones. Los altos contenidos de proteínas, lípidos y carbohidratos observados en el seston al final del estudio, pudieran estar principalmente asociados con la surgencia costera que provee un gran aporte alimenticio de tipo fitoplanctónico y orgánico. El alto porcentaje de supervivencia (>80%), el incremento de la longitud de la concha y la alta producción de tejido reproductivo, sugieren una excelente condición fisiológica de P. viridis, relacionada con la disponibilidad y la calidad del alimento particularmente de tipo orgánico presente en el medio, por lo que el cultivo de fondo puede constituir una alternativa de producción acuícola en el golfo de Cariaco.

Characterization of ten highly polymorphic microsatellite loci for the intertidal mussel Perna perna, and cross species amplification within the genus.

BACKGROUND: The brown mussel Perna perna (Linnaeus, 1758) is a dominant constituent of intertidal communities and a strong invader with multiple non-native populations distributed around the world. In a previous study, two polymorphic microsatellite loci were developed and used to determine population-level genetic diversity in invasive and native P. perna populations. However, higher number of microsatellite markers are required for reliable population genetic studies.In this context, in order to understand P. perna origins and history of invasion and to compare population genetic structure in native versus invaded areas, we developed 10 polymorphic microsatellite markers. FINDINGS: Described microsatellite markers were developed from an enriched genomic library. Analyses and characterization of loci using 20 individuals from a population in Western Sahara revealed on average 11 alleles per locus (range: 5-27) and mean gene diversity of 0.75 (range: 0.31 - 0.95). One primer pair revealed possible linkage disequilibrium while heterozygote deficiency was significant at four loci. Six of these markers cross-amplified in P. canaliculus (origin: New Zealand). CONCLUSIONS: Developed markers will be useful in addressing a variety of questions concerning P. perna, including dispersal scales, genetic variation and population structure, in both native and invaded areas.

Complete mitochondrial genome of the Asian green mussel Perna viridis (Bivalvia, Mytilidae).

The complete mitochondrial (mt) genome of the Asian green mussel Perna viridis (16,627 bp), an economically important bivalve, was newly sequenced and annotated. P. viridis is the shortest and has a comparatively highest overall A+T content (68%) among six available genomes of marine mussels to date. The atp8 gene's length (49 a.a.) of the green mussel is unexpectedly greatly shorter than that of other marine mussels (87 a.a.). Comparison of the gene order demonstrated that the six marine mussels share no identical gene blocks although they belong to the same family, which indicates that this group should be a good model to study mtDNA evolution and mitochondria inheritance.

[Growth and survival of the green mussel P. viridis (Bivalvia: Mytilidae) in bottom culture conditions in Turpialito, Golfo de Cariaco, Venezuela]. / Crecimiento del mejillón verde Perna viridis (Bivalvia: Mytilidae) bajo sistema de cultivo de fondo en la ensenada de Turpialito, Golfo de Cariaco, Venezuela.

Mussels represent one of the most important mollusk species for culture activities around the world, and their growth may depend on the culture system used and locality. In this study, we evaluated the growth of Perna viridis in bottom culture to test its performance when using natural food, and to decide its use as a culture species in the Gulf of Cariaco. For this, mussel seeds (35.81 +/- 1.41 mm in length) were obtained in the locality of Guaca (North coast of Sucre state) and transferred to the Hydrobiological Station of Turpialito, Gulf of Cariaco, Sucre state, Venezuela, where they were planted in "Spanish baskets" to evaluate their growth between July 2007 and February 2008. Monthly survival was determined and the maximum shell length, dry mass of muscle and remains tissues of the gonad. The environmental parameters (water temperature, salinity, dissolved oxygen, chlorophyll a, total seston and organic fraction), in the cultivation area were determined every 15 days. Monthly measurements were made of proteins, lipids and carbohydrates to seston. During the entire study the mussels showed continued growth, ultimately reaching a maximum length of 78.7 +/- 4.43 mm. However, the growth rate of the dry mass of somatic (muscle, other tissue) and reproductive tissues showed variability throughout the study, and observed a significant increase by the end of the experiment. The observed variations in the growth rate of the reproductive tissue mass depended on the reserves accumulated and food offered by the environment. The organic seston throughout the experience showed an independence of temperature and chlorophyll a values; this one maintained values above 1 mg/L, thus forming the main food resource for mussels. The high content of proteins, lipids and carbohydrates observed in the seston at the end of the study, might be mainly associated with coastal upwelling, which provides a great food contribution of phytoplankton and organic type. The high survival rate (>80%), increase in the length of the shell and the high gonad production, suggests an excellent physiological condition of P. viridis, related to the availability and quality of food particularly the organic type present in the medium. We concluded that the bottom culture can provide an alternative aquaculture production in the Gulf of Cariaco.

Comparative study of various immune parameters in three bivalve species during a natural bloom of Dinophysis acuminata in Santa Catarina Island, Brazil.

This study aimed to verify if Dinophysis acuminata natural blooms affected the immune system of three bivalves: the oyster, Crassostrea gigas, the mussel, Perna perna, and the clam, Anomalocardia brasiliana. Animals were obtained from a renowned mariculture farm in the southern bay of Santa Catarina Island during, and 30 days after (controls), an algal bloom. Various immunological parameters were assessed in the hemolymph of the animals: total and differential hemocyte counts, percentage of apoptotic hemocytes, protein concentration, hemagglutinating titer and phenoloxidase activity. The results showed that the mussel was the most affected species, with several altered immune parameters, whereas the immunological profile of clams and oysters was partially and completely unaffected, respectively.

Spatial and temporal genetic variation of green mussel, Perna viridis in the Gulf of Thailand and implication for aquaculture.

The culture of green mussel (Perna viridis) in the Gulf of Thailand depends on natural spat which are believed to come from spawning grounds adjacent to major river mouths. In the present paper, genetic diversity of spatial and temporal populations of green mussel in the Gulf of Thailand was investigated using five microsatellite loci. The results showed moderate genetic variation of all 11 populations (averaged number of alleles per locus, A = 10.4-12.2; effective number of alleles per locus, A(e) = 5.36-6.59; mean allelic richness, A(r) = 10.23-12.06; observed heterozygosity, H(o) = 0.52-0.63, and expected heterozygosity, H(e) = 0.66-0.73) without significant differences among populations. No sign of bottleneck or genetic disequilibrium was observed. Genetic differentiation among spatial populations was low (F (ST) = 0.0046, CI(0.95) = 0.0020-0.0083 for the samples collected in January, 2007, and F (ST) = 0.0088, CI(0.95) = 0.0010-0.0162 for the samples collected in July, 2007) while temporal variation was significant as revealed by the analysis of molecular variance. Multidimensional scaling separated temporal population groups with minor exception. The assignment test revealed that most of the recruits were from other populations.

Molecular discrimination of Perna (Mollusca: Bivalvia) species using the polymerase chain reaction and species-specific mitochondrial primers.

This work was prompted by the need to be able to identify the invasive mussel species, Perna viridis, in tropical Australian seas using techniques that do not rely solely on morphology. DNA-based molecular methods utilizing a polymerase chain reaction (PCR) approach were developed to distinguish unambiguously between the three species in the genus Perna. Target regions were portions of two mitochondrial genes, cox1 and nad4, and the intergenic spacer between these that occurs in at least two Perna species. Based on interspecific sequence comparisons of the nad4 gene, a conserved primer has been designed that can act as a forward primer in PCRs for any Perna species. Four reverse primers have also been designed, based on nad4 and intergenic spacer sequences, which yield species-specific products of different lengths when paired with the conserved forward primer. A further pair of primers has been designed that will amplify part of the cox1 gene of any Perna species, and possibly other molluscs, as a positive control to demonstrate that the PCR is working.