Chilean Blue Mussel Research Articles

Identification and expression analysis of two steamer-like retrotransposons in the Chilean blue mussel (Mytilus chilensis)

BackgroundDisseminated neoplasia (DN) is a proliferative cell disorder of the circulatory system of bivalve mollusks. The disease is transmitted between individuals and can also be induced by external chemical agents such as bromodeoxyuridine. In Mya arenaria, we have cloned and characterized an LTR-retrotransposon named Steamer. Steamer mRNA levels and gene copy number correlates with DN and can be used as a marker of the disease. So far, the only mollusk where a retrotransposon expression relates to DN is Mya arenaria. On the other hand, it has been reported that the Chilean blue mussel Mytilus chilensis can also suffers DN. Our aim was to identify retrotransposons in Mytilus chilensis and to study their expression levels in the context of disseminated neoplasia.ResultsHere we show that 7.1% of individuals collected in August 2018, from two farming areas, presents morphological characteristics described in DN. Using Steamer sequence to interrogate the transcriptome of M. chilensis we found two putative retrotransposons, named Steamer-like elements (MchSLEs). MchSLEs are present in the genome of M. chilensis and MchSLE1 is indeed an LTR-retrotransposon. Neither expression, nor copy number of the reported MchSLEs correlate with DN status but both are expressed at different levels among individual animals. We also report that in cultured M. chilensis haemocytes MchSLEs1 expression can be induced by bromodeoxyuridine.ConclusionsWe conclude that SLEs present in Mytilus chilensis are differentially expressed among individuals and do not correlate with disseminated neoplasia. Treatment of haemocytes with a stressor like bromodeoxyuridine induces expression of MchSLE1 suggesting that in Mytilus chilensis environmental stressors can induce activation of LTR-retrotransposon.

The Mytilus chilensis Steamer-like Element-1 Retrotransposon Antisense mRNA Harbors an Internal Ribosome Entry Site That Is Modulated by hnRNPK.

LTR-retrotransposons are transposable elements characterized by the presence of long terminal repeats (LTRs) directly flanking an internal coding region. They share genome organization and replication strategies with retroviruses. Steamer-like Element-1 (MchSLE-1) is an LTR-retrotransposon identified in the genome of the Chilean blue mussel Mytilus chilensis. MchSLE-1 is transcribed; however, whether its RNA is also translated and the mechanism underlying such translation remain to be elucidated. Here, we characterize the MchSLE-1 translation mechanism. We found that the MchSLE-1 5' and 3'LTRs command transcription of sense and antisense RNAs, respectively. Using luciferase reporters commanded by the untranslated regions (UTRs) of MchSLE-1, we found that in vitro 5'UTR sense is unable to initiate translation, whereas the antisense 5'UTR initiates translation even when the eIF4E-eIF4G interaction was disrupted, suggesting the presence of an internal ribosomal entry site (IRES). The antisense 5'UTR IRES activity was tested using bicistronic reporters. The antisense 5'UTR has IRES activity only when the mRNA is transcribed in the nucleus, suggesting that nuclear RNA-binding proteins are required to modulate its activity. Indeed, heterogeneous nuclear ribonucleoprotein K (hnRNPK) was identified as an IRES trans-acting factor (ITAF) of the MchSLE-1 IRES. To our knowledge, this is the first report describing an IRES in an antisense mRNA derived from a mussel LTR-retrotransposon.

Authentication of Frozen Chilean Blue Mussel (Mytilus chilensis) Commercialized in the Town of Osorno, Southern Chile, Using PCR-RFLP Analysis.

DNA-based technologies are reliable authentication methods for food products, enabling the detection of fraud, non-intentional substitution and control of mislabeling. The Chilean blue mussel (Mytilus chilensis) is a seafood commercialized in Chile under different formats, including packages of frozen specimens. In this format, the valves of mussels are removed during processing, thus impeding identification of the product by the consumer due to the lack of external characters. To assess the authenticity of frozen Chilean blue mussels commercialized in southern Chile, particularly in the town of Osorno. Six commercial brands of frozen Chilean blue mussel were authenticated by the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method, based on the analysis of an 18S rDNA fragment. Restriction patterns obtained indicate that three brands (50%) proved to be 100% authentic, given that all specimens contained in the package were Chilean blue mussels. The other three brands (50%) contained specimens of other commercial mytilids, particularly the cholga mussel (Aulacomya ater), in a variable percentage (12.5-50%). This study based on the PCR-RFLP method provides evidence that Chilean blue mussels commercialized in a town located in southern Chile lack authenticity. This finding highlights the necessity for national producers to improve the production and/or packaging processes of this seafood. The authentication of commercial mussels is a matter of consumer interest and has been described in a recent patent on this issue that proposes an alternative methodology.

The impact of trade and markets on Chilean Atlantic salmon farming

Since the 1980s, aquaculture has developed rapidly around the world, outpacing all other sources of animal protein production. Chile is the largest producer in South America, with an export-driven aquaculture industry. Aquaculture development in Chile has largely focussed on three high-value species (Atlantic salmon, Rainbow trout and Chilean blue mussel). These three species accounted for over 90% of the volume and value of Chilean exports by 2014. The paper considers the role of trade and markets on Atlantic salmon production in Chile and the role of government regulators and industry to facilitate a further sustainable increase in farmed salmon output. Specifically, we address the opportunities and constraints regarding the impact of trade and markets for further industry expansion. We find that production constraints (e.g. regulation, over-production), marketing constraints (e.g. consumer perception) and environmental constraints (e.g. disease) have led to stagnating and sometimes declining production, preventing Chile from surpassing Norway and becoming the world’s largest Atlantic salmon producer. The paper concludes that the signs for further growth are positive in Chile, although to date, it is noted that industry expansion has outpaced developments in infrastructure, regulation and research and development. Most significantly, the industry has been blighted with environmental problems, which has weakened market share in recent years. However, better regulatory practice in Chile in recent years has been seen as positive in international markets. We note that further development in the regulatory framework and continued aspirations to meet certification standards (e.g. Aquaculture Stewardship Council, Global Aquaculture Alliance Certification) could lead to increased market share for Chilean farmed salmon in the future.

Greenhouse gases, nutrients and the carbonate system in the Reloncaví Fjord (Northern Chilean Patagonia): Implications on aquaculture of the mussel, Mytilus chilensis, during an episodic volcanic eruption

This study investigates the immediate and mid-term effects of the biogeochemical variables input into the Reloncaví fjord (41°40′S; 72°23′O) as a result of the eruption of Calbuco volcano. Reloncaví is an estuarine system supporting one of the largest mussels farming production within Northern Chilean-Patagonia. Field-surveys were conducted immediately after the volcanic eruption (23–30 April 2015), one month (May 2015), and five months posterior to the event (September 2015). Water samples were collected from three stations along the fjord to determine greenhouse gases [GHG: methane (CH4), nitrous oxide (N2O)], nutrients [NO3−, NO2−, PO43−, Si(OH)4, sulphate (SO42−)], and carbonate systems parameters [total pH (pHT), temperature, salinity, dissolved oxygen (O2), and total alkalinity (AT)]. Additionally, the impact of physicochemical changes in the water column on juveniles of the produced Chilean blue mussel, Mytilus chilensis, was also studied. Following the eruption, a large phytoplankton bloom led to an increase in pHT, due to the uptake of dissolved-inorganic carbon in photic waters, potentially associated with the runoff of continental soil covered in volcanic ash. Indeed, high surface SO42− and GHG were observed to be associated with river discharges. No direct evidence of the eruption was observed within the carbonate system. Notwithstanding, a vertical pattern was observed, with an undersaturation of aragonite (ΩAr < 1) both in brackish surface (<3 m) and deep waters (>10 m), and saturated values in subsurface waters (3 to 7 m). Simultaneously, juvenile mussel shells showed maximized length and weight at 4 m depth. Results suggest a localized impact of the volcanic eruption on surface GHG, nutrients and short-term effects on the carbonate system. Optimal conditions for mussel calcification were identified within a subsurface refuge in the fjord. These specific attributes can be integrated into adaptation strategies by the mussel aquaculture industry to confront ocean acidification and changing runoff conditions.

Native and invasive taxa on the Pacific coast of South America: Impacts on aquaculture, traceability and biodiversity of blue mussels (Mytilus spp.)

AbstractGaining new knowledge of the native distributions of species (phylogeography) is more and more difficult in a world affected by anthropogenic disturbance, in particular by species translocations. Increasingly, molecular markers are required to support decisions about the taxonomy of native vs. introduced species, and the existence of their hybrids, to answer phylogeographic questions. In many fields, including aquaculture, traceability and food security, taxonomic and phylogeographic knowledge is key to the successful management and conservation of biodiversity. The Pacific coast of Chile is one of the last regions without a clear and agreed understanding of the taxonomy and systematics of smooth‐shelled blue mussels of the genus Mytilus. A panel of 49 bi‐allelic single nucleotide polymorphisms (SNPs) was genotyped in 338 Mytilus individuals collected from nine Chilean and five reference populations. All analyses confirmed the hypothesis that the native Chilean blue mussel is genetically distinct from the reference species M. edulis, M. galloprovincialis and M. trossulus. These results support the hypothesis of a unique evolutionary history of the native Chilean blue mussel on the Pacific coast of South America. It is therefore concluded that the native blue mussel from Chile should be recognized as M. chilensis Hupé 1854. We confirmed a recent Mediterranean origin of introduced M. galloprovincialis on the coast of Chile. This knowledge advances the understanding of global phylogeography of blue mussels and their bioinvasions and harmonizes taxonomy in the context of aquaculture production, seafood traceability, labelling and trade.

Effect of ohmic heating on texture, microbial load, and cadmium and lead content of Chilean blue mussel (Mytilus chilensis)

Abstract The effect of ohmic heating (OH) on the texture, microbial load, and cadmium (Cd) and lead (Pb) content was evaluated in Chilean blue mussel ( Mytilus chilensis ) at shucking and subsequent canning. Mussel samples were processed by OH and blanching (BLAN) at 50 ± 1 °C, 70 ± 1 °C and 90 ± 1 °C for shucking and then canning at 115 °C for 20 min. The Cd and Pb content in fresh mussels was 2.47 ± 0.18 μg g − 1 and 5.26 ± 0.55 μg g − 1 dry weight (dw). The greatest reduction in Cd content was reached at 90 ± 1 °C by OH with 1.67 ± 0.06 μg g − 1 (dw) and 1.69 ± 0.08 μg g − 1 (dw) by BLAN. At the same temperature, the Pb content was reduced to 4.18 ± 0.24 μg g − 1 dw for OH and 4.14 ± 0.30 μg g − 1 dw for BLAN. The cutting strength of fresh samples (21.35 ± 2.44 N) significantly decreased in samples processed by OH (15.65 ± 1.36 N) at 90 ± 1 °C compared with BLAN samples (20.41 ± 3.16 N) at the same temperature. The initial mean count for mesophilic aerobic microorganisms and Enterobacteriaceae was 3.8 log cfu/g and 2.5 log cfu/g, respectively. The mesophilic aerobic microorganism count was reduced by 1.7 logarithmical units, while Enterobacteriaceae counts were reduced to undetectable levels by OH at 90 ± 1 °C. Industrial relevance High temperature short time (HTST) processes rely on rapid convection heat transfer and are thus well suited to liquid foods. But, they are, however, limited in application to particulates since, for particles more than a couple of millimeters thick, the processing time is insufficient for heat to transfer to the center to give sterility. Ohmic heating is an emerging technology and very promising in food industries. It is a thermal process in which heat is generated internally in food and acts as a resistance to the flow of alternating electric current. This type of treatment prevents overheating by producing less deterioration in food components. It is a rapid procedure that allows food to conserve its natural properties; microorganisms and enzymes are also inactivated. The purpose of the present work was to evaluate the effect of Ohmic heating on mechanical properties, microbial load, Cd and Pb content in the opening and subsequent canning of Chilean blue mussel ( Mytilus chilensis ). This information could be used for the seafood industries in order to improve thermal heating processes in mussels.

Microsatellites ofMytilus chilensis: A Genomic Print of Its Taxonomic Status withinMytilussp.

The taxonomic status of the Chilean blue mussel Mytilus chilensis has been controversial for decades because of its phenotypic and genetic proximity to other species of the genus Mytilus from both hemispheres. This study reports the development of nine polymorphic microsatellite markers from the M. chilensis genome. The number of alleles per locus ranged between four and nine, and the observed heterozygosity ranged from 0.182–0.750 in a wild sample of 24 individuals from Caicaén (Chiloé Region, Chile). Lack of efficient amplification of many of these microsatellite loci in other Mytilus species suggests that M. chilensis is a valid, distinct species within the genus. These new markers would be useful in fine-scale population analyses of M. chilensis as well in the aquaculture management of this marine resource.

Cadmium bioaccumulation and retention kinetics in the Chilean blue mussel Mytilus chilensis: Seawater and food exposure pathways

The Chilean blue mussel ( Mytilus chilensis, Hupe 1854) represents the most important bivalve exploited along the Chilean coast and is a major food source for the Chilean population. Unfortunately, local fish and shellfish farming face severe problems as a result of bioaccumulation of toxic trace metals into shellfishes. Blue mussels collected along the Chilean coasts contain levels of Cd above the regulatory limits for human consumption. In this study, we examined the bioaccumulation, depuration and organ distribution of Cd in the M. chilensis, from 109Cd-labelled bulk seawater and from feeding with 109Cd-labelled algae. The uptake of 109Cd via seawater displayed a simple exponential kinetic model suggesting that cadmium activity tends to reach an equilibrium value of 1.838 ± 0.175 ng g −1 (mean ± asymptotic standard error, p < 0.001) after 78 ± 9 days. The depuration rate for 109Cd accumulated via seawater was slow, with only 21% of the total 109Cd accumulated in the whole mussel being eliminated after 52 days. Total elimination of Cd in mussels was adequately described by a double component kinetic model, in which the biological half-life for the long-lived component represents more than 6 months. In contrast, depuration after radiolabelled food uptake was fast, reaching only 20% of retention in 10 days. This knowledge of the long half-life of cadmium accumulated via seawater as well as the non-negligible level of cadmium accumulated into the shells is relevant to the management of Cd levels in this species and the refinement of detoxification processes in order to comply with authorized Cd levels.

Shell-shape variation along the latitudinal range of the Chilean blue mussel Mytilus chilensis (Hupe 1854)

Abs tra ctShell -sh ap e variation in th e C h ilean blue m u sselMyt ilu s chi len sis w as exam ined in eight popu la-tions coverin g th e tota lity of its distribu tion ran ge,which repr esen ts ov er 1800 km of la titu din al gradi-en t in the sou thea ste rn Paci¢c . The sh ell ou tlinesh ap es w ere assessed us in g elliptic Fou rier an alysisfollow ed by can on ica l variates an a lysis. Fou riercoeU cien ts show ed a h igh ly sign i¢ca n t m orpholo gi-cal variation be tw een the popu lations stud ied.Ca n on ica lva riates an alysis show ed a visu alassocia-tion of th e First ca n on ica l w ith con vexity of ven traledge an d u mbo sh ap e,w h ile the second axis w as as-sociated w ith sh ell elon gation . P reviously describe dge net ic pa tterns were m argin ally con gru en t w ithou r m orphomet ric pattern , thou gh ge o graph ic dis-ta n ce h ad a stron ge r eAect on m orphol ogy . Sh apech an ge (elon gation ) w as correlated w ith latitu din alclin alvariation .The m orphomet rica lan alysis provedto be an im portan t to ol for ev alu atin g th e com po -ne n ts of shell -sh ape va riation in m u ssels and todocu me n t association pa tterns w ith ge ogr aph ica lan d ecolo gica lva riables. Such pa tterns a re u sefu ltoestablish a w ide ¢eld ofw ork ,in clu d in g sexin g,sto ckrec og n ition , traceab ility stu dies an d prod uc tivem an age me n t in ge ner al.K e y w ord s: in ter-grou p d iscrim in ation , im agea n a lysis, ou tlin es, elliptic Fou rier a n a lysis, ca n on i-cal va riates an alysis, biog eogr aph y, M ytilus chilen-sis,blu e muss elsIntroductionThe C h ilean blue m u ssel Myt ilu s chilensis (H u pe185 4) is w idely distribu ted on h ard subs trates fromth e low er in tertida lzone to depth s o f25 m alon g theC h il ea nco s(Br rþm & Joh 1983). Ir ang e the S E P c i¢c vrs 4 0 1 f l ude ,f rom A ica ( 18 S)to Cape H n56 (La cellott iV et l .6 ) The if-f e rnt iaion pa tte ws c orel ted ith aph -cal d ista n ce, su gges tin g a steppin g-stone m odel ofth e pop u lation stru ctu re. Th is m odel w a s exp ecteddue to th e large dispersalability o flon g-lived plan kto -troph ic la rvae a n d th e pattern o f ocean cu rren tsalon g the C h i le nco s (Toro et .200 4, 0 6) I ad-d ition , a nly sof hell mrphol gy u lnea or -phomet ic v ab l es on three po u ions w nsou ther nC hile ar g how d oupopu lation (P u n ta A ren a s) w as th e m os t d iverge n t(Toro et al.200 4).In th e presen t study w e exam in ed shell m orphol -ogy variation to see if it follow ed th e sa m e pattern ofge net ic m ark ers alon g the 18 00 -k m grad ien t.To da te,m ost m orpholo gica l an alyses of Myti lus sp. shel lsh ave be en ba sed on she ll linea r m orphomet ric

Heritability of body size in the Chilean blue mussel (Mytilus chilensisHupé 1854): effects of environment and ageing

Selection, either natural or artificial, induces an inter-generational response only when the trait exhibits additive genetic variation. An index of additive genetic variation is narrow-sense heritability (h2): the ratio between additive genetic variance and phenotypic variance. Here, we present narrow-sense heritabilities for mass and size in the Chilean blue mussel Mytilus chilensis at different ages and in three different populations. We found that h2 changed with age and that maternal-non-additive variance was high, generating relatively low estimates of h2 in most cases. Our results, together with previous studies, suggest that genotype-by-environment interaction does not appear to play a significant role. However, we found that non-additive and common environmental variance are important determinants of phenotypic morphological variation in body size in M. chilensis. Further studies are needed to establish the precise contributions of these sources of variation, to assess the real potential for response to selection.

Allozymic variation and differentiation in the chilean blue mussel, Mytilus chilensis, along its natural distribution

Genetic differentiation in the Chilean blue mussel Mytilus chilensis (Hupe 1854) was investigated based on the variation in the allozyme frequencies of Pgm, Gpi, Icd, Me, Gsr, Lap and Pep in eight samples collected along 1800 km from Arauco (VIII Region) to Punta Arenas (XII Region). Despite the large geographic separations, values of Neis unbiased genetic distance, D (0.004-0.048) and standardised genetic variation among populations, Fst (0.011-0.055) were small. The levels of gene flow (Nm = 8) found in this study prevent the effect of differentiation among populations by genetic drift. This findings indicate that its long-lived planktotrophic larvae provides this species with considerable dispersal ability throughout its range which is favoured by the ocean currents along the chilean coast. In terms of management of the M. chilensis fishery, the results provide no evidence for discrete stocks, with the possible exception of the Punta Arenas population. Considering the intensive aquaculture activities with this species the present study provide preliminary data which can be used as a baseline for further characterization and /or monitoring these mussel populations.

MOLECULAR CHARACTERIZATION OF THE CHILEAN BLUE MUSSEL (MYTILUS CHILENSIS HUPE 1854) DEMONSTRATES EVIDENCE FOR THE OCCURRENCE OF MYTILUS GALLOPROVINCIALIS IN SOUTHERN CHILE

The Chilean blue mussel formerly Mytilus chilensis Hupe 1854, have been recently subject to a taxonomic revision using electrophoretically generated genetic data concluding that mussels from South America should be included tentatively in Mytilus edulis. The molecular genetic characterization (restriction fragment length polymorphism) of samples from 8 natural populations along the whole natural distribution of the Chilean blue mussel using 3 PCR-based nuclear DNA markers (ITS, Glu-5 and Me) was carried out. One of the markers (ITS) showed a similar banding pattern than M. edulis and M. galloprovincialis, whereas the other markers (Glu-5 and Me) showed a specific banding pattern found only in M. galloprovincialis. Also, a very low number (3.9%) of mussel hybrids (M. edulis–M. galloprovincialis) using two codominant markers was detected in the present study. The molecular evidence suggests that M. galloprovincialis is present in the southern coast of Chile, whereas no evidence for the occurrence of Mytilus trossulus was found.

The genetic structure of Mytilus chilensis (Hupe 1854) populations along the Chilean coast based on RAPDs analysis

The Chilean blue mussel Mytilus chilensis is an important commercial species. However, little has been published on the population genetics of this species, despite the need to implement management and conservation policies. Randomly amplified polymorphic DNA-polymerase chain reaction analysis was used to estimate genetic variation within and between eight natural populations along the whole range of its Chilean natural distribution (ca. 1900 km from Arauco (VIII Region) to Punta Arenas (XII Region)). The values of Nei's unbiased genetic distance, D (0.030–0.107), among populations were small, despite the large geographic separation. A mantel test using 50 000 randomizations showed evidence for a significant correlation (r=0.74, P<0.05) between genetic and geographic (coastal) distance. Punta Arenas population was the most genetically differentiated from the others, although the scale of differentiation was not large (D=0.076–0.107). The levels of gene flow (Nm=1.55) found in this study prevent differentiation among populations by genetic drift. This is the result of the long-lived planktotrophic larvae of M. chilensis, which provides this species with considerable dispersal ability throughout its range, which is favoured by the ocean currents along the Chilean coast. A restricted larval dispersal towards the north due to the Cape Horn Current derived from the West Wind Drift could be the cause of the higher genetic differentiation of Punta Arenas population from the northern populations. For management purposes of the M. chilensis fishery, the results provide no evidence for discrete stocks, with the possible exception of the Punta Arenas population. The present study provides the baseline data in order to continue further characterization of these mussel populations, considering the great increase in aquaculture of this species.

Heritability estimates of larval and spat shell height in the Chilean blue mussel (Mytilus chilensis Hupe 1854) produced under controlled laboratory conditions

The heritability of larval size is estimated in Mytilus chilensis, based on a nested design, involving 95 full-sib and 19 half-sib families (19 males each mated to 5 separated females) grown under controlled laboratory conditions. The half-sib heritability estimates at 10, 25 and 40 days for larval and spat shell height ranged between 0.38±0.33 and 0.84±0.45, suggesting that selection for shell size would be effective.

PCR-based nuclear and mtDNA markers and shell morphology as an approach to study the taxonomic status of the Chilean blue mussel, Mytilus chilensis (Bivalvia)

Most recent authors have called the Chilean blue mussel (formerly Mytilus chilensis) Mytilus edulis. Mussels from four nominal species ( Mytilus edulis, M. trossulus, M. galloprovincialis and M. chilensis) were collected from the eastern coast of Newfoundland, Canada, New Zealand and the southern coast of Chile. Canonical discriminant analysis of selected shell morphometrical characters showed that although there is some overlap in canonical variates, the three nominal species, M. edulis, M. trossulus and M. chilensis can be morphologically divided into three distinct groups. The two nuclear-DNA markers ( ITS and Glu-5) and the mtDNA marker studied indicate that the nuclear and mitochondrial genomes of M. edulis and M. trossulus are different. M. edulis, M. galloprovincialis and M. chilensis share similar restriction fragment patterns for the mtDNA and for the ITS nuclear-DNA marker, while the Glu-5 polymerase chain reaction (PCR) assay showed that the M. edulis and M. chilensis genotypes disagree, producing species-specific banding patterns that can be used as a diagnostic marker between the two nominal species. The molecular and morphometric data reported here give more evidence to support the view of other authors that the Chilean blue mussel should be included as M. edulis subspecies: Mytilus edulis chilensis.

Feeding Trial with Different Families of Chilean Blue Mussel,Mytilus chilensisLarvae

The effect of different concentrations of phytoplankton as food for different groups of Chilean blue mussel, Mytilus chilensis, larvae in terms of the increase in shell length over a 20-day period were studied. Three concentrations (6,250, 25,000 and 100,000 cell/mL) of microalgae (Isochrysis aff. galbana) were fed to twelve half-sib families. A significant variation in shell size was observed among the treatments within families (P < 0.05), as was observed between similar treatments among families within males (P < 0.05). Mussel larvae fed I. aff. galbana exhibit a marked decrease in mortalities when fed increased concentrations of the phytoplankton. These data suggest that the use of I. aff. galbana at sufficient densities (> 25,000 cell/mL) to overcome mortality can benefit the growth of Chilean blue mussel larvae.