Mytilus Chilensis Research Articles

Spatial distribution pattern of Mytilus chilensis beds in the Reloncaví fjord: hypothesis on associated processes

Natural M. chilensis populations dominate habitats with a steep environmental gradient, and that are characterized by abrupt changes in salinity and exposure to desiccation. Although these populations are the source of seed supplies for the Chilean mussel culture industry (annual production around 250 thousand Tons), knowledge about natural populations is scarce. Based on video transect recordings, this study carries out research into one of the principal mussel beds and its associated epibenthic community in the Reloncaví Fjord, both along cross-shore and along-shore distribution gradients. Mytiluschilensis was observed between the middle intertidal zone and the upper subtidal zone (between approximately 9 and 26 psu), with a richer associated community towards the subtidal zone and the fjord mouth. The mussel Condition Index (total meat weight/shell length*100) in the intertidal zone was significantly greater than in the subtidal zone, which raises questions about the reproductive contribution of mussels along the intertidal mid-subtidal gradient. Salinity and tidal variations, together with biological interactions, would seem to be key factors for explaining M. chilensis spatial distribution in the Reloncaví fjord, where beds appear to be in a contraction stage, as evidenced by M. chilensis scarcity towards the subtidal zone. The importance of these populations and their persistence in environments with high perturbation frequency, suggests a monitoring program should be implemented that considers both population spatial distribution and the changing environmental conditions.

Histopathological survey of the mussel Mytilus chilensis (Mytilidae) and the clam Gari solida (Psammobiidae) from southern Chile

A total of 175 specimens of mussels, Mytilus chilensis (Mytilidae), and 56 specimens of clams, Gari solida (Psammobiidae), were collected in natural beds and culture sites of southern Chile. Juvenile mussel specimens (3 cm of maximum length) were free of parasites and diseases, whilst the commercial sized populations was parasitized by intracellular inclusions of bacteria-like organisms in the digestive gland epithelium and in the gills, by ciliates in the gills, turbellarians similar to Paravortex (Rhabocoela) in the intestine lumen and copepods attached to the gills. In addition, the disseminated neoplasia disease was also present although in low prevalences. In the clam, G. solida, prokariotic inclusions were found in the digestive gland epithelium and bacteria-like organisms in the gills, often encapsulated by haemocytes; oocysts containing up to 8 sporozoites similar to Nematopsis (Apicomplexa) in the connective tissue, causing haemocytic infiltration when the intensity of infection was high; ciliates belonging to two different species (one of them similar to Trichodina) inhabiting the gills; and a turbellarian similar to Paravortex in the lumen of digestive system without apparent host reaction. The populations of the bivalve species here studied were devoid of serious pathogens.

Reproduction and oxidative metabolism in the brooding sea star Anasterias antarctica (Lütken, 1957)

The oral-brooding sea star Anasterias antarctica is distributed on the coasts of South Patagonia and north of Antarctic Peninsula. This species is a potential predator of shellfish Mytilus chilensis, an important commercial resource for Beagle Channel region. The aims of this work were to study the variation in the gonad index (GI), to establish the brooding season, to determine the reproductive effort of both sexes, and to assess the concentration of liposoluble antioxidants and production of reactive oxygen species (ROS) in male and female gonads and embryos of A. antarctica during the year. Four samplings were performed: three during the brooding season and one during the non-brooding season. Individuals sampled during the brooding season were assigned to one of the three groups: brooding females, non-brooding females, and males. Individuals sampled during the non-brooding season were assigned to one of the three groups: sexually mature females, sexually non-mature females and males.Histological observations allowed determining that only females incubate the embryos on the oral surface for seven months. Males showed a strategy characteristic of broadcast spawners, whereas females spawned only a small number of eggs, as it is characteristic of brooders and as observed in other species of asteroids. Males show a significant increase in GI before spawning (from 1% to 15%) and then a marked decrease. During gametogenesis, testes showed a low level of β-carotene and high production of ROS. Between May and October; brooding and non-brooding females showed similar values of ROS production and concentration of antioxidants. Mature females had a significantly higher GI and lipid soluble antioxidant concentration than non-mature females. ROS production was higher in non-mature females. In A. antarctica embryos, ROS production increased and liposoluble antioxidant defenses decreased along development. The reproductive effort of males was about 25% lower than that of females, probably because of brooding costs. Gonadal maturation occurred in summer in both sexes, in concordance with an increase in the concentration of liposoluble antioxidants and the minimum values of ROS production. This suggests a strategy of oxidative damage prevention and gamete protection through allocation of antioxidants to mature gonads. The β-carotene and α-tocopherol accumulation in ovaries would protect not only maturing oocytes but also embryos, given that these antioxidants would be transferred to eggs. Along the reproductive cycle, A. antarctica gonads are protected from oxidative processes, mainly by β-carotene. Further, during gonad maturation, protection increases with the increase in α-tocopherol concentration and the decrease in ROS, whose highest and lowest values coincide with maximum gonadal maturation.

Genetic considerations for mollusk production in aquaculture: current state of knowledge.

In 2012, world mollusk production in aquaculture reached a volume of 15,171,000 tons, representing 23% of total aquaculture production and positioning mollusks as the second most important category of aquaculture products (fishes are the first). Clams and oysters are the mollusk species with the highest production levels, followed in descending order by mussels, scallops, and abalones. In view of the increasing importance attached to genetic information on aquaculture, which can help with good maintenance and thus the sustainability of production, the present work offers a review of the state of knowledge on genetic and genomic information about mollusks produced in aquaculture. The analysis was applied to mollusks which are of importance for aquaculture, with emphasis on the 5 species with the highest production levels. According to FAO, these are: Japanese clam Ruditapes philippinarum; Pacific oyster Crassostrea gigas; Chilean mussel Mytilus chilensis; Blood clam Anadara granosa and Chinese clam Sinonovacula constricta. To date, the genomes of 5 species of mollusks have been sequenced, only one of which, Crassostrea gigas, coincides with the species with the greatest production in aquaculture. Another important species whose genome has been sequenced is Mytilus galloprovincialis, which is the second most important mussel in aquaculture production, after M. chilensis. Few genetic improvement programs have been reported in comparison with the number reported in fish species. The most commonly investigated species are oysters, with at least 5 genetic improvement programs reported, followed by abalones with 2 programs and mussels with one. The results of this work will establish the current situation with respect to the genetics of mollusks which are of importance for aquaculture production, in order to assist future decisions to ensure the sustainability of these resources.

Distribution and growth of Vibrio parahaemolyticus in southern Chilean clams (Venus antiqua) and blue mussels (Mytilus chilensis).

We evaluated the distribution and growth of Vibrio parahaemolyticus in the inland sea of southern Chile, where the world's largest foodborne gastroenteritis outbreak by the pandemic strain O3:K6 occurred in 2005. Intertidal samples of Mytilus chilensis and Venus antiqua were collected around port towns between 41°28'S and 43°07'S, during April to May 2011 and January to March 2012. We used most probable number real-time polymerase chain reaction (MPN-PCR) for enumeration of the tlh, tdh, and trh genes in freshly harvested bivalves and after a controlled postharvest temperature abuse. Pathogenic markers (tdh+ or trh+) were not detected. Total V. parahaemolyticus (tlh+) in freshly harvested samples reached up to 0.38 and 3.66 log MPN/g in 2011 and 2012, respectively, with values close to or above 3 log MPN/g only near Puerto Montt (41°28'S, 72°55'W). Enrichments by temperature abuse (>2 log MPN/g) occurred mainly in the same zone, regardless of the year, suggesting that both natural or anthropogenic exposure to high temperatures were more critical. Lower salinity and higher sea surface temperature in Reloncaví Sound and Reloncaví Estuary were consistent with our observations and allowed confirmation of the existence of a high-risk zone near Puerto Montt. Based on the results, a strategy focused on risk management inside this defined hazard zone is recommended.

Intraspecific Variability in the Response of the Edible Mussel Mytilus chilensis (Hupe) to Ocean Acidification

Ocean acidification (OA) has been shown to affect significantly the net calcification process and growth rate of many marine calcifying organisms. Recent studies have shown that the responses of these organisms to OA can vary significantly among species. However, much less is known concerning the intraspecific variability in response to OA. In this study, we compared simultaneously the responses of two populations of the edible mussel Mytilus chilensis (Hupe) exposed to OA. Three nominal CO2 concentrations (380, 700, and 1,000 μatm of CO2) were used. Negative effects of CO2 increase on net calcification rate were only found in individuals from Huelmo Bay. However, no effects were found in individuals from Yaldad Bay. Moreover, OA had not significant effects on the shell dissolution rate in individuals from both localities. This suggests that the negative effect of the OA on the net calcification rate of this species is explained by shell deposition, but not by the shell dissolution processes. We do not know the specific underlying mechanisms responsible for these differences, but some possibilities are discussed. These results highlight that the responses of marine organism to OA can be highly variable even within the same species. Therefore, more studies across the distribution range of the species, considering environmental variability, are needed for a better understanding of the consequences of OA on marine organisms. Finally, because mussels exert influence on their physical and biological surroundings, the negative effects of a CO2 increase could have significant ecological consequences.

Complete Genome Sequence of Vibrio anguillarum Phage CHOED Successfully Used for Phage Therapy in Aquaculture

Vibrio anguillarum phage CHOED was isolated from Chilean mussels. It is a virulent phage showing effective inhibition of V. anguillarum. CHOED has potential in phage therapy, because it can protect fish from vibriosis in fish farms. Here, we announce the completely sequenced genome of V. anguillarum phage CHOED.

Acid and Enzyme-Aided Collagen Extraction from the Byssus of Chilean Mussels (Mytilus Chilensis): Effect of Process Parameters on Extraction Performance

Recovery of high-added-value compounds from seafood waste is a promising area of research. Mussel byssus is a by-product from mussel production for human consumption, which is a potential source of collagen. The goal of this study was to extract collagen from the byssus of Chilean mussel using two methods (acidic and enzymatic) and determine their extraction yields. Acidic extraction was performed by immersing the byssus into distilled water adjusted to pH 4 with HCl at two extraction temperatures (60 or 80 °C) and times (6 or 24 h). For enzymatic extraction, first an enzymatic hydrolysis at two times (4 or 24 h) and pepsin/substrate ratios (1:50 or 4:50) was done. Then, the extraction was conducted at 80 °C for 24 h. All samples were analyzed for total protein, amino acid profile and molecular weight of collagen extracts. Extraction time and temperature had significant effects (p < 0.05) on protein and hydroxyproline contents after acidic extraction, where the higher level of process parameters (80 °C and 24 h) gave the highest protein (6 mg/mL) and hydroxyproline (7.6 mg/g protein) values. Using an enzymatic step before extraction, an increase in protein and hydroxyproline contents was observed, with maximum values of 31 mg/mL and 32 mg/g protein, respectively. The enzyme extraction presented the higher extraction yield, values ranging from 3.86 to 7.56 %. Electrophoretic patterns of collagen presented only β and γ bands, suggesting that this collagen is highly cross-linked at the telopeptide region. These results indicate that the Chilean mussel byssus is a good source of collagen that can be extracted for different purposes.

Feeding and intoxication–detoxification dynamics in two populations of the mussel Mytilus chilensis (Hupé, 1854) with different histories of exposure to paralytic shellfish poisoning (PSP)

Individuals of Mytilus chilensis with different histories of exposure to paralytic shellfish poisoning (PSP) were exposed to a diet containing the dinoflagellate Alexandrium catenella. Feeding and intoxication–detoxification dynamics were evaluated over a period of 12–16 days. Feeding activity was reduced during the first days of exposure, followed by a period of recovery from day 5 to the end of the experiment. Mussels from Corral population (no history of PSP exposure) exceeded the concentration of 80 μg STX eq. 100 g−1 tissue, although filtration activity was significantly lower compared with individuals from Melinka (frequent PSP exposure). The higher feeding activity and the lower degree of toxin accumulation in the Melinka population appear be associated with frequent exposure to PSP in the natural environment. The use of A. catenella as food resource and the capacity of a rapid intoxication of both populations showed that M. chilensis is an adequate indicator for early detection of PSP.

Use of cellulolytic marine bacteria for enzymatic pretreatment in microalgal biogas production.

In this study, we designed and evaluated a microalgal pretreatment method using cellulolytic bacteria that naturally degrades microalgae in their native habitat. Bacterial strains were isolated from each of two mollusk species in a medium containing 1% carboxymethyl cellulose agar. We selected nine bacterial strains that had endoglucanase activity: five strains from Mytilus chilensis, a Chilean mussel, and four strains from Mesodesma donacium, a clam found in the Southern Pacific. These strains were identified phylogenetically as belonging to the genera Aeromonas, Pseudomonas, Chryseobacterium, and Raoultella. The cellulase-producing capacities of these strains were characterized, and the degradation of cell walls in Botryococcus braunii and Nannochloropsis gaditana was tested with "whole-cell" cellulolytic experiments. Aeromonas bivalvium MA2, Raoultella ornithinolytica MA5, and Aeromonas salmonicida MC25 degraded B. braunii, and R. ornithinolytica MC3 and MA5 degraded N. gaditana. In addition, N. gaditana was pretreated with R. ornithinolytica strains MC3 and MA5 and was then subjected to an anaerobic digestion process, which increased the yield of methane by 140.32% and 158.68%, respectively, over that from nonpretreated microalgae. Therefore, a "whole-cell" cellulolytic pretreatment can increase the performance and efficiency of biogas production.

Seasonal effects of the seeding on the growth of Chilean mussel ( Mytilus edulis platensis, d'Orbigny 1846) cultivated in central Chile

Abstract This study presents a background on growing Mytilus edulis platensis , which were seeded on both summer and winter seasons. Surface longline systems were installed at a lower latitude zone than mussel aquaculture industries along Llico bay, VIII region (Biobio) of Chile. Mussel seeds were transferred from X region (Los Lagos) the traditional region for culture mussels. The first seeding was carried out in February (summer) and the second in July 2009 (winter). In the culture period, shell length, total weight and weight of fresh meat were measured. During the study, seeded mollusks in summer and winter seasons grew 3.03 and 4.37 mm month − 1 , on average, respectively. It was observed that for the same asymptotic length ( L ∞ = 79.1 mm), the value of the metabolic constant was higher in winter ( k Li = 0.1995) than in summer ( k Lv = 0.1492), and for the same asymptotic weight ( W ∞ = 40.79 g), the k value was higher in winter than in summer ( k wi = 0.1643 and k wv = 0.1392, respectively). Cultivation time and seeding season have a significant effect on growth in both length and total weight ( p p > 0.05). It can be concluded that seeding in winter has a positive effect on growth, decreasing the cultivation time for a harvest size more than the commercial size in 3 months (shell length ≥ 50 mm).

Differences in sperm ultrastructure between Mytilus chilensis and Mytilus galloprovincialis (Bivalvia, Mytilidae): could be used as a taxonomic trait

The sperm ultrastructure has been used to solve several systematic and phylogenetic problems in marine invertebrates. The sperm ultrastructure of the Chilean mussel Mytilus chilensis and Mytilus galloprovincialis corresponds to the ect-aquasperm type. Sperm from both taxa measured 55-60 µm between head (acrosome + nucleus), midpiece (only 5 mitochondria) and the flagellum which in its end piece has a smaller diameter tail. The differences between both taxa are clearly shown, in the structure of the acrosome and nucleus. Therefore, according to our results and those reported in the literature, we indicate that Chilean native mussel sperm is different from other species of the Mytilus complex (M. trossulus, M. galloprovincialis and M. edulis). These differences in sperm ultrastructure found in M. chilensis, are another trait that can be used to validate the taxonomic status of the species. Differences in sperm morphology are related with reproductive isolation, and probably will be useful to understand future data on speciation. Finally, we discussed the finding that Mytilus galloprovincialis sperm from Chile have an acrosome notoriously smaller than those reported for specimens from Europe and Africa, though they have a great similarity with specimens from Japan, as reported in the literature.

Traceability of mussel (Mytilus chilensis) in southern Chile using microsatellite molecular markers and assignment algorithms. Exploratory survey

The international seafood trade has adopted the food chain or “from farm to fork” concept in terms of standards and regulations regarding food quality, safety and authenticity, from primary production to the consumer. This has led to an increasing need for traceability, but administrative traceability systems (physical labeling, information recording and automatic data treatment) are not flawless and require validation through analytical procedures. Currently, DNA-based methods used for species identification and population genetics, coupled with allocation algorithms can be used to verify administrative traceability systems. We evaluated the potential of a panel of nine microsatellite markers combined with allocation algorithms for their ability to assign Mytilus individuals from southern Chile to their geographical origin, evaluating the performance of four assignment methods: genetic distance and frequency-based criteria and a Bayesian based method using prior information or not. The reallocation test showed that the Bayesian method with prior information performed best. When tested with a real traceability verification case, the frequency-based algorithm showed the best results, re-allocating individuals to their original population at least 6 times more often than individuals from other locations in a challenging scenario with low genetic differentiation among locations. In order to apply this allocation method for traceability purposes, it would be necessary to strengthen this SSR panel with more informative loci and complement it with SNP markers.

Pre-feasibility Study for the Installation of a Chilean Mussel Mytilus chilensis (Hupe, 1854) Seed Hatchery in the Lakes Region, Chiles

Chile is the fourth world’s largest producer of mussels, concentrating 90% of the production of Mytilus chilensis, the Chilean mussel or Patagonian mussel, in the Lakes Region (40°13’ to 44°3’ S, 74°49’ to 71°34’ W). The mussel seed production in Chile depends exclusively on natural collection and currently faces a serious seed shortage crisis, with a decrease of 15% in natural collection during 2012. This study evaluated the pre-feasibility of producing Chilean mussel seed in hatchery. Results showed that although there is technical, legal, environmental, political and managerial viability, the current financial conditions are not adequate to produce mussel seed under modeled hatchery conditions, the NPV: Net Present Value is >0. Seed production in hatchery was not profitable due to both the low price of Chilean mussels in national and international markets and the high cost of production, mainly associated to the production of microalgae (91% of total cost of production). Therefore, despite the significant economic and social impact of the mussel production in Chile and its 20% annual growth, the activity is threatened by the high variability in natural settlement and the economic infeasibility posed by the current seed production technology under controlled conditions.

The myostatin gene of Mytilus chilensis evidences a high level of polymorphism and ubiquitous transcript expression

Myostatin (MSTN) is a protein of the Transforming Growth Factor-β (TGF-β) superfamily and plays a crucial role in muscular development for higher vertebrates. However, its biological function in marine invertebrates remains undiscovered. This study characterizes the full-length sequence of the Mytilus chilensis myostatin gene (Mc-MSTN). Furthermore, tissue transcription patterns and putative single nucleotide polymorphisms (SNPs) were also identified. The Mc-MSTN cDNA sequence showed 3528 base pairs (bp), consisting of 161bp of 5′ UTR, 2110bp of 3′ UTR, and an open reading frame of 1257bp encoding for 418 amino acids and with an RXXR proteolytic site and nine cysteine-conserved residues. Gene transcription analysis revealed that the Mc-MSTN has ubiquitous expression among several tissues, with higher expression in the gonads and mantle than in the digestive gland, gills, and hemolymph. Furthermore, high levels of polymorphisms were detected (28 SNPs in 3′-UTR and 9 SNPs in the coding region). Two SNPs were non-synonymous and involved amino acid changes between Glu/Asp and Thr/Ile. Until now, the MSTN gene has been mainly related to muscle growth in marine bivalves. However, the present study suggests a putative biological function not entirely associated to muscle tissue and contributes molecular evidence to the current debate about the function of the MSTN gene in marine invertebrates.

Population structure, growth and production of a recent brachiopod from the Chilean fjord region

AbstractMagellania venosa, the largest recent brachiopod, occurs in clusters and banks in population densities of up to 416 ind m−2 in Comau Fjord, Northern Chilean fjord region. Below 15 m, it co‐occurs with the mytilid Aulacomya atra and it dominates the benthic community below 20 m. To determine the question of why M. venosa is a successful competitor, the in situ growth rate of the brachiopod was studied and its overall growth performance compared with that of other brachiopods and mussels. The growth in length was measured between February 2011 and March 2012 after mechanical tagging and calcein staining. Settlement and juvenile growth were determined from recruitment tiles installed in 2009 and from subsequent photocensus. Growth of M. venosa is best described by the general von Bertalanffy growth function, with a maximum shell length (L∞) of 71.53 mm and a Brody growth constant (K) of 0.336 year−1. The overall growth performance (OGP index = 5.1) is the highest recorded for a rynchonelliform brachiopod and in the range of that for Mytilus chilensis (4.8–5.27), but lower than that of A. atra (5.74). The maximal individual production (PInd) is 0.29 g AFDM ind−1 year−1 at 42 mm shell length and annual production ranges from 1.28 to 89.25 g AFDM year−1 m−2 (1–57% of that of A. atra in the respective fjords). The high shell growth rate of M. venosa, together with its high overall growth performance may explain the locally high population density of this brachiopod in Comau Fjord. However, the production per biomass of the population (‐ratio) is low (0.535) and M. venosa may play only a minor role in the food chain. Settling dynamics indicates that M. venosa is a pioneer species with low juvenile mortality. The coexistence of the brachiopod and bivalve suggests that brachiopod survival is affected by neither the presence of potential brachiopod predators nor that of space competitors (i.e. mytilids).

Identification of immune-related SNPs in the transcriptome of Mytilus chilensis through high-throughput sequencing

Single nucleotide polymorphisms (SNPs) identified in coding regions represent a useful tool for understanding the immune response against pathogens and stressful environmental conditions. In this study, a SNPs database was generated from transcripts involved in the innate immune response of the mussel Mytilus chilensis. The SNPs were identified through hemocytes transcriptome sequencing from 18 individuals, and SNPs mining was performed in 225,336 contigs, yielding 20,306 polymorphisms associated to immune-related genes. Classification of identified SNPs was based on different pathways of the immune response for Mytilus sp. A total of 28 SNPs were identified in the Toll-like receptor pathway and included 5 non-synonymous polymorphisms; 19 SNPs were identified in the apoptosis pathway and included 3 non-synonymous polymorphisms; 35 SNPs were identified in the Ubiquitin-mediated proteolysis pathway and included 4 non-synonymous variants; and 54 SNPs involved in other molecular functions related to the immune response, such as molecular chaperones, antimicrobial peptides, and genes that interacts with marine toxins were also identified. The molecular markers identified in this work could be useful for novel studies, such as those related to associations between high-resolution molecular markers and functional response to pathogen agents.

Transcriptional responses of Mytilus chilensis exposed in vivo to saxitoxin (STX)

Saxitoxin (STX) is one of the main phycotoxins that contribute to paralytic shellfish poisoning (PSP). This toxin is mainly produced by marine microalgae of the genus Alexandrium. There is evidence of changes at the physiological level in bivalves exposed to STX, although transcriptional responses to STX in bivalves have not yet been studied. The present work evaluates the expression of 13 candidate genes associated with cellular stress and immune response in Mytilus chilensis exposed to STX. Analysis by qPCR showed higher gene transcription levels in M. chilensis injected with STX than in control mussels. High levels of differential gene expression were observed for superoxide dismutase, catalase, ferritin and heat-shock protein genes. To a lesser extent, ependymin, fibrinogen-like, galectin and mytilin B genes were also significantly more expressed in haemocytes of mussels injected with STX that in control mussels. Our results provide insights into how marine toxins could modulate the innate immune system of marine invertebrates.

Determination of the variability of both hydrophilic and lipophilic toxins in endemic wild bivalves and carnivorous gastropods from the Southern part of Chile

The aim of this study was to analyse and determine the composition of paralytic shellfish poisoning (PSP) toxins and lipophilic toxins in the Region of Aysén, Chile, in wild endemic mussels (Mytilus chilensis, Venus antiqua, Aulacomya ater, Choromytilus chorus, Tagelus dombeii and Gari solida) and in two endemic carnivorous molluscs species (Concholepas concholepas and Argobuccinum ranelliforme). PSP-toxin contents were determined by using HPLC with fluorescence detection, while lipophilic toxins were determined by using LC-MS/MS. Mean concentrations for the total of PSP toxins were in the range 55–2505 μg saxitoxin-equivalent/100 g. The two most contaminated samples for PSP toxicity were bivalve Gari solida and carnivorous Argobuccinum ranelliforme with 2505 ± 101 and 1850 ± 137 μg saxitoxin-equivalent/100 g, respectively (p < 0.05). The lipophilic toxins identified were okadaic acid, dinophysistoxin-1 (DTX-1), azaspiracid-1 (AZA-1), pectenotoxin-2 (PTX-2) and yessotoxins (YTX). All analysed molluscs contained lipophilic toxins at levels ranging from 56 ± 4.8 to 156.1 ± 8.2 μg of okadaic acid-equivalent/kg shellfish together with YTX at levels ranging from 1.0 ± 0.1 to 18 ± 0.9 μg of YTX-equivalent/kg shellfish and AZA at levels ranging from 3.6 ± 0.2 to 31 ± 2.1 μg of AZA-equivalent/kg shellfish. Furthermore, different bivalves and gastropods differ in their capacity of retention of lipophilic toxins, as shown by the determination of their respective lipophilic toxins levels. In all the evaluated species, the presence of lipophilic toxins associated with biotransformation in molluscs and carnivorous gastropods was not identified, in contrast to the identification of PSP toxins, where the profiles identified in the different species are directly related to biotransformation processes. Thus, this study provides evidence that the concentration of toxins in the food intake of the evaluated species (Bivalvia and Gastropoda class) determines the degree of bioaccumulation and biotransformation they will thereafter exhibit.

Combined effects of temperature and ocean acidification on the juvenile individuals of the mussel Mytilus chilensis

Anthropogenic CO2 emissions have led to increasing global mean temperatures (a process called global warming) and ocean acidification. Because both processes are occurring simultaneously, to better understand their consequences on marine species their combined effects must be experimentally evaluated. The aim of this study was to evaluate for the first time the combined effects of ocean acidification and water temperature increase on the total calcification rate, growth rate and survival of juvenile individuals of the mytilid mussel Mytilus chilensis (Hupe). Two temperature levels (12 and 16°C) and three nominal CO2 concentrations (390, 700 and 1000ppm of CO2) were used. We found that the net rate of calcium deposition and total weight were not significantly affected by temperature, but were negatively affected by the levels of CO2. The interactive effects of temperature and CO2 levels affected only the shell dissolution, but this process was not important for the animal's net calcification. These results suggest that individuals of M. chilensis are able to overcome increased temperatures, but not increments of CO2 levels. It is well known that mussels influence their physical and biological surroundings. Therefore, the negative effects of a CO2 increase could have significant ecological consequences, mainly in those habitats where this group is dominant in terms of abundance and biomass. Finally, taking into account that this species inhabit a wide geographic range, with contrasting environmental conditions (e.g., temperature, salinity and, pH), further studies are needed to evaluate the intraspecific variability in the responses of this species to different environmental stressors.