Peruvian Scallop Argopecten Purpuratus Research Articles

Reproductive Conditioning of the Peruvian Scallop Argopecten purpuratus in Different Environments

Obtaining viable Argopecten purpuratus seeds faces challenges, especiallyci the unpredictability of the marine environment and high production costs in hatcheries. However, improving the method of "Broodstock Conditioning In Hatcheries" is key to ensure permanent seed supplies by minimizing the dependence on marine conditions and by maximizing economic viability in hatcheries. In an effort to overcome these barriers, broodstock were conditioned into two different environments: (a) Natural Environment: Natural marine conditions located in Bahía Inglesa, Atacama Region, Chile. (b) Hatchery: Laboratory conditions to achieve gonadal maturation, spawning induction, fertilization and larval development. The purpose of this research was to evaluate how the type of reproductive conditioning affects the reproductive potential and nutritional quality of the progeny. Both methods were successful at inducing the necessary maturity for reproduction, obtaining viable gametes and larvae. On the other hand, it was observed that in the natural environment, the oocytes and D larvae reached a greater size and nutritional value, being the most significant differences with (p < 0.05): the size of the D larvae reached figures of 95.8 ± 3.1 μm and 91.2 ± 2.7 μm in the environment and hatchery, respectively; the lipid content in dry mass was 25.2 ± 3.1 mg g−1 and 13.5 ± 1.9 mg g−1 for the natural environment and hatchery, respectively. Although quality indicators in hatcheries were slightly lower compared to the natural environment, the possibility of conditioning A. purpuratus broodstock independently of environmental variability highlights the importance of further optimizing broodstock conditioning aspects in hatcheries that would allow more predictable and sustainable production.

Effect of low pH on growth and shell mechanical properties of the Peruvian scallop Argopecten purpuratus (Lamarck, 1819)

Dissolution of anthropogenic CO2 modifies seawater pH, leading to ocean acidification, which might affect calcifying organisms such as bivalve mollusks. Along the Peruvian coast, however, natural conditions of low pH (7.6–8.0) are encountered in the habitat of the Peruvian scallop (Argopecten purpuratus), as a consequence of the nearby coastal upwelling influence. To understand the effects of low pH in a species adapted to these environmental conditions, an experiment was performed to test its consequences on growth, calcification, dissolution, and shell mechanical properties in juvenile Peruvian scallops. During 28 days, scallops (initial mean height = 14 mm) were exposed to two contrasted pH conditions: a control with unmanipulated seawater presenting pH conditions similar to those found in situ (pHT = 7.8) and a treatment, in which CO2 was injected to reduce pH to 7.4. At the end of the experiment, shell height and weight, and growth and calcification rates were reduced about 6%, 20%, 9%, and 10% respectively in the low pH treatment. Mechanical properties, such as microhardness were positively affected in the low pH condition and crushing force did not show differences between pH treatments. Final soft tissue weights were not significantly affected by low pH. This study provides evidence of low pH change shell properties increasing the shell microhardness in Peruvian scallops, which implies protective functions. However, the mechanisms behind this response need to be studied in a global change context.

Evaluation of bacterial strains to improve the productivity of microalgae used in bivalve hatcheries in Peru

AbstractThe microalgae Isochrysis galbana and Chaetoceros gracilis are part of the basic diet of most bivalve cultures. This study evaluated the supplementation of bacterial strains naturally associated with these microalgae to improve their productivity. Ten bacterial strains collected from I. galbana and C. gracilis commercial cultures used in the larviculture of the Peruvian scallop Argopecten purpuratus were isolated and purified. These strains were individually coinoculated to each microalgal culture to confirm their promoter effect on growth. First, inoculation was carried out in a volume of 500 mL with constant aeration, which allowed the selection of the best bacterial strains. Then, the culture growth performance after transfer from 500 mL to 2 L tanks, with and without bacterial reinoculation during transfer, was monitored. Two bacterial strains, Lysinibacillus fusiformis and Bacillus cereus, significantly improved (α = .05) I. galbana production, whereas three other strains, Lysinibacillus sp., Psychrobacter celer, and Staphylococcus saprophyticus, significantly increased (α = .05) the growth of the C. gracilis culture. The use of microalgae supplemented with bacteria did not significantly affect A. purpuratus larval rearing. Altogether, these results showed the potential of native probiotic bacteria to improve microalgal production within bivalve hatcheries.

Trophic interactions and metal transfer in marine ecosystems driven by the Peruvian scallop Argopecten purpuratus aquaculture

AbstractThis study investigates the trophic interactions and As and Cd transfer along seven marine ecosystems in Peru. Five of these ecosystems are driven by aquaculture of the Peruvian scallop Argopecten purpuratus. A southward increased gradient of δ15N was observed among the three examined regions along the Peruvian coast. The stable isotope analysis in R (SIAR)‐stable isotope mixing models helped to clarify the feeding ecology of A. purpuratus and its important predators (e.g., Bursa ventricosa, Romaleon setosum). The food items of A. purpuratus can be ranked in decreasing order of importance: seston > sediment > particulate organic matter (POM) > brackish‐and‐fresh water POM input, while A. purpuratus itself was found to be the main prey item for predators. The highest trophic magnification factors (TMFs) were 1.46 and 1.07 for As and Cd, respectively, and were both found at the location in front of the Illescas Reserve Zone (northern Peru). Metal biomagnification and non‐biomagnification effects were found in the Peruvian marine food webs, but A. purpuratus always fitted the trophic metal magnification or bio‐dilution regression model as intermediate consumer and/or prey. The TMFs and linear metal relationships implied that As contamination is a serious concern in marine ecosystems in Peru.

The Effect of Hybridization between Natural and Cultivated Peruvian Scallop Argopecten purpuratus populations on Growth and Tolerance to Abiotic Stress

Intraspecific hybridization has been a strategy used frequently in mollusc aquaculture to improve the performance of traits for productive interest. In this study, the effect of hybridization between a natural population (Arica = A) and a cultivated population (Coquimbo = C; without genetic management for more than 30 y) of the Peruvian scallop Argopecten purpuratus was evaluated to assess the effect of this strategy on the performance of the cultivated population in terms of growth, survival, and stress tolerance due to hypoxia and increased temperature. To this end, progenies from intrapopulation (C × C and A × A) and reciprocal hybrid (C × A and A × C) crosses were produced and were evaluated after 6 mo under sea cultivation and in a controlled environment. Stress responses were evaluated via metabolic rates and the transcriptional level of stress-associated genes [superoxide dismutase (SOD) and HSP70]. The results showed that CC and the reciprocal hybrids CA and AC had greater size and survival rates than AA; on the other hand, AA presented the highest metabolic rates when exposed to stress; and, in parallel, AA and both hybrids (CA and AC) presented greater antioxidant capacity (SOD) when exposed to hyperthermia. Therefore, growth and survival showed positive heterosis because the hybrids performed better in these traits than the parental mean. In addition, hybridization with the Arica population would allow the Coquimbo stock under cultivation to improve its resilience to temperature increases associated to oceanographic oscillations or to climate change.

Microbial characterization of a natural biofilm associated with Peruvian scallop (Argopecten purpuratus) larvae settlement on artificial collector by confocal imaging, microbiology, and metagenomic analysis

Biofilms strongly influence bivalve settlement patterns on artificial substrates; however, their structure and taxonomic composition remains a black box. We characterized a natural biofilm composition that exhibits a large settlement of larvae of the Peruvian scallop Argopecten purpuratus by culture-dependent and culture-independent methods. Thirty-two different strains, representing six genera (10 strains of Bacillus, 9 of Vibrio, 6 Acinetobacter, 4 Staphylococcus, 2 Photobacterium, and 1 Exiguobacterium) were isolated. Those strains represented only 1.09% of the relative abundance compared with the total microbiota obtained by 16S rRNA high-throughput sequencing. The metagenomic analysis identified 441 species. Prokaryotes were predominant (93.4%) over eukaryotes (6.6%), with Pelobacter (13.4%), Lewinella (5.6%), Marinobacter (5.4%), Hoeflea (4.2%), and Microcystis (3.1%) being the most representative genera. Laser scanning confocal microscopy (LSCM) imaging evidenced an irregular and heterogeneous biofilm with an average thickness of 35 μm, where the heterotrophic prokaryotic community (3.4×106 cell cm-2) dominate the photoautotrophic communities (2.3×105 cell cm-2). For the first time, an A. purpuratus settlement-related biofilm was described by the next generation sequencing tool (NGS) and compared with traditional methodologies.

Peruvian scallop Argopecten purpuratus: From a key aquaculture species to a promising biondicator species

The present study analyzed the Peruvian scallop Argopecten purpuratus and its food sources for metal and fatty acid concentrations in order to determine spatial and temporal differences. Metals such as copper (Cu), manganese (Mn), and zinc (Zn) in gills and iron (Fe) and Zn in sediments were the most significant explaining factors for spatial differentiations (degree of contamination), while for fatty acids, it was C14:0, C15:0, C16:0 and C18:0 in A. purpuratus' muscle and in its food sources, which explained more temporal differences (El Niño-Southern Oscillation (ENSO) effect). Gills, digestive gland and intestine were the tissues where metal accumulation was the highest in A. purpuratus. Cd in digestive gland was always high, up to ∼250-fold higher than in other tissues, as previously reported in other bioindicator species for metal pollution. Fatty acids were good biomarkers when annual comparisons were performed, while metals when locations were compared. ENSO 2017 played an important role to disentangle A. purpuratus’ biological conditions and food sources. A. purpuratus from Paracas locations mostly showed higher metal concentrations in gills and digestive glands, and lower fatty acid concentrations in muscle than those from Sechura and Illescas Reserved Zone.

Impact of High Feeding on the Locomotive Capacity of the Juvenile Peruvian Scallop Argopecten purpuratus after Exposure to Hypoxia

The scallop Argopecten purpuratus is a species of high commercial interest in northern Chile and Peru. Both natural and cultured populations are located in shallow bays which are periodically subjected to decreases in the levels of dissolved oxygen and to variations in the availability of food, due to upwelling events or large-scale oscillations such as El Nino–Southern Oscillation. The aim of the present study was to evaluate how the nutritional status of A. purpuratus juveniles affects their escape capacity (as a measure of their vitality) after exposure to hypoxia cycles such as those encountered in their natural environment. For this, three feeding levels were applied for 15 days: scallops fed with a mixture of microalgae equivalent to (1) 6% or (2) 3% of their body mass and (3) unfed scallops. Subsequently, half of the individuals in each treatment underwent daily hypoxia cycles for 7 days and the other half was maintained under normoxia. After this period, using their predator, the sea star Meyenaster gelatinosus, the scallops were induced to escape, and several escape response indicators were evaluated. In general, scallops fed with the highest microalgal ration (6% of scallop mass) showed the best escape performance in terms of the reaction time to the predator, total number of claps, and clapping time and rate, closely followed by scallops fed 3% of their mass. Unfed scallops showed the poorest performance in each of these escape parameters. These results were closely related with the carbohydrate content of the adductor muscle, with unfed scallops showing the lowest content. Hypoxia exposure resulted in a decrease in escape response, and unfed scallops were the most affected. Among unfed scallops, 40% of the individuals maintained under normoxia showed an escape response, whereas only 15% of those exposed to hypoxia escaped the predator. By contrast, and regardless of environmental oxygenation, more than 90% of individuals fed with either 3% or 6% rations escaped the predator. In conclusion, when scallops are under reduced nutritional state (due to low food availability), the cyclical hypoxic periods that they encounter in the natural environment can have profound effects on their vitality, making them more vulnerable against predators.

First report of the metacestode Caulobothrium sp. in the Peruvian scallop Argopecten purpuratus from Sechura Bay, Piura, Peru.

In recent parasitological surveys performed on the Peruvian scallop, Argopecten purpuratus, from bottom cultures of Sechura Bay, Piura, Peru, free and encysted metacestodes were frequently found in their gonads. The objective of this study was to identify this metacestode, determine their prevalence and intensity and briefly assess the histopathological impact in the affected tissues. A parasitological study of 890 scallops over a 3-year period was performed in order to determine the parasite prevalence and intensity. Microscopical observation of details of the scolex and histopathological study of the affected hosttissues were performed as well as molecular characterization of the parasitebased on 18S and 28S rDNA sequences. The prevalence of the metacestode was 82.2% in August of 2013, 90.4% in November of 2014, and 83.1% and 85.6% in April and September of 2015, respectively. The highest average intensity (218.4) was found in spring of 2014. The histopathological study showed that plerocercoids reduced the gonadal space where the ovules develop. The molecularcharacterization and phylogenetic analysis revealed that the metacestodes belong to the genus Caulobothrium having high sequence similarity to Caulobothrium opisthorchis. This study constitutes the first report of Caulobothrium metacestodes in the scallop A. purpuratus.

Predicting the energy budget of the scallop Argopecten purpuratus in an oxygen–limiting environment

Low concentrations of oxygen determine marine species distribution and abundance along the Peruvian coast with consequences for human activity such as fishing and aquaculture. In order to assess bioenergetic consequences of oxygen limitation on the Peruvian scallop Argopecten purpuratus, we first developed a Dynamic Energy Budget (DEB) model of growth and reproduction calibrated on field experimental datasets. Then, we included oxygen availability as an additional forcing variable using a simple rule based on the ability of the scallop to regulate oxygen consumption. The resulting model was tested using growth/reproduction monitoring and simultaneous high frequency environmental records in Paracas Bay (Peru) at two different depths: suspended in the water column and on the sea bottom. Simulations indicated that scallops' growth and reproduction was not food-limited. The negative observed effects of hypoxia on growth and reproduction could be explained by a decrease in both assimilation and reserve mobilization. However, hypoxic conditions in summer were not sufficient to explain the observed losses in somatic tissue weights and the disruption of reproduction. The latter two patterns were better simulated when assuming increased somatic maintenance costs due to the presence of H2S during milky turquoise water discolouration events observed during summer.

Mitochondrial genome of the Peruvian scallop Argopecten purpuratus (Bivalvia: Pectinidae)

The mitochondrial genome of the Peruvian scallop Argopecten purpuratus was determined. The length of the mitochondrial coding region is 15,608 bp. A typical bivalve mitochondrial composition was detected with 12 protein-coding genes, 2 ribosomal RNA genes and 21 transfer RNA genes, with the absence of the atp8 gene. Fifty percent of the protein-coding genes use typical ATG start codon, whereas five genes utilize ATA as their start codon. Only one gene was found to utilize TTG as its start codon. The A. purpuratus mitogenome shows a significant similarity to that of A. irradians irradians, in length as well as in gene composition.

Genetic structure of the Peruvian scallop Argopecten purpuratus inferred from mitochondrial and nuclear DNA variation

The population genetic structure of the Peruvian scallop Argopecten purpuratus from three different wild populations along the Peruvian coast was analyzed using nine microsatellite loci and a partial region (530bp) of the mitochondrial 16S rRNA gene. A total of 19 polymorphic sites in the 16S rRNA gene defined 18 unique haplotypes. High genetic diversity was presented in all populations. Statistical analysis of mitochondrial DNA revealed no significant genetic structure (ΦST=0.00511, P=0.32149) among the three localities. However, microsatellite analysis showed low (2.86%) but highly significant (P=0.0001) genetic differentiation among populations, most of the variation was found in Independencia Bay population, which is located in the Peruvian National Reserve of Paracas. Neutrality tests based on mitochondrial haplotypes were performed to assess signatures of recent historical demographic events. Overall results from Tajima's D and Fu's FS tests indicated significant deviations from neutrality. To our knowledge, this study constitutes the first investigation based on mitochondrial and microsatellite markers on the genetic structure of A. purpuratus.

Isolation and characterization of 12 microsatellite loci in the Peruvian scallop Argopecten purpuratus and cross-species amplification in other scallop species (family Pectinidae)

Argopecten purpuratus is an economically important marine bivalve. Twelve microsatellite loci were isolated and characterized in 20 individuals of A. purpuratus collected in Isla Independencia (Pisco, Peru) and tested for cross-species amplification in other 4 scallops (family Pectinidae). Ten loci were polymorphic. The number of alleles per locus ranged from 2 to 13. The observed (HO) and expected (HE) heterozygosities ranged from 0.100 to 0.900 and from 0.185 to 0.903, respectively. Two loci showed significant deviation from Hardy–Weinberg equilibrium. A low rate of cross-species amplification was found.

Energy vs. essential fatty acids: what do scallop larvae ( Argopecten purpuratus) need most?

Larvae of the Chilean–Peruvian scallop Argopecten purpuratus were fed a Dunaliella tertiolecta diet (Dun-diet) supplemented with lipid emulsions, rich in 20:5n-3 (EmEPA), 22:6n-3 (EmDHA) or in saturated fatty acids (EmCOCO). A mixed algal diet of Isochrysis galbana (T-iso) and Chaetoceros neogracile served as a positive control (St-diet). Lipid supplementation to the Dun-diet improved the larval growth and increased the percentage of eyed larvae significantly, compared to the non-supplemented Dun-diet because of the extra energy supplied and not because of its fatty acid composition. No significant differences were observed between supplementation with EmEPA, EmDHA or EmCOCO. A mixture of 20% EmEPA+20% EmDHA (40% EmHUFA) was more efficient in raising the total lipid content in larvae than 40% EmCOCO. Both emulsions increased the triacylglycerol content in larvae compared to the non-supplemented Dun-diet. The best result, however, was obtained with the St-diet, probably because of a more suitable 18:2n-6/18:3n-3 ratio and a higher level of arachidonic acid. A positive relationship between the 18:2n-6/18:3n-3 ratio and the larval performance was found. No significant difference was observed in post-settlement larval size or percentage of metamorphosed larvae between the St-diet and the St-diet supplemented with 20% EmHUFA or 20% EmCOCO. The metamorphosed larvae had a constant DHA/EPA ratio of 3.7, independent from the diet, which suggested a metabolic control of the two fatty acids and a species-dependency of the ratio.

Spawning and recruitment in the Peruvian scallop Argopecten purpuratus

During a 15 mo period (February 1983 to May 1984), spawning and recruitment pulses of the Peruvian scallop Argopecten purpuratus were determined using information on gonad index, larval abundance and recruitment of scallop seed on the natural banks. In situ temperature was simultaneously recorded and showed a marked relation with spawning time as well as to recuperation time between successive spawnings. This study shows that A. purpuratus is a continuous spawner with spawning peaks that are only partially reflected in the recruitment pattern, indicating that spawning intensity and success of subsequent recruitment are not closely related.