Search

The remarkable mechanical adaptability of arapaima (Arapaima gigas) scales has made them an important subject of study. However, no research has been conducted into their tribological properties, which are crucial for the protectability and flexibility of arapaimas. In this study, by combining morphological characterizations, friction experiments, and theoretical analyses, the relationship between the surface morphology and tribological properties of arapaima scales is determined. These results indicate that arapaima scales exhibit varying surface morphologies in different regions. More specifically, the exposed regions of scales feature grooves and a circulus, whereas the covered regions exhibit bumps. The specific surface morphology of arapaima scales produces varying tribological properties across different regions and sliding directions. The unique tribological properties of arapaima scales influence the forces received from predator attacks and neighboring scales, directly influencing the arapaima's protective capabilities. This study provides new insights into the mechanisms of natural flexible dermal armors, and it has potential applications in personal protective systems. [ABSTRACT FROM AUTHOR]

Accurate species phylogenies are a prerequisite for all evolutionary research. Teleosts are the largest and most diversified group of extant vertebrates, but relationships among their three oldest extant lineages remain unresolved. On the basis of seven high-quality new genome assemblies in Elopomorpha (tarpons, eels), we revisited the topology of the deepest branches of the teleost phylogeny using independent gene sequence and chromosomal rearrangement phylogenomic approaches. These analyses converged to a single scenario that unambiguously places the Elopomorpha and Osteoglossomorpha (arapaima, elephantnose fish) in a monophyletic sister group to all other teleosts, i.e., the Clupeocephala lineage (zebrafish, medaka). This finding resolves more than 50 years of controversy on the evolutionary relationships of these lineages and highlights the power of combining different levels of genome-wide information to solve complex phylogenies. [ABSTRACT FROM AUTHOR]

Communities throughout the globe are increasingly being given the responsibility of resource management, making it necessary to understand the factors that lead to success in community-based management (CBM). Here, we assessed whether and how institutional design principles affect the ecological outcomes of CBM schemes for Arapaima sp., an important common-pool fishery resource of the Amazon Basin. We quantified the degree of presence of Ostrom's (Science 325:419–422, 1990) institutional design principles in 83 communities using a systematic survey, and quantitatively linked the design principles to a measure of ecological outcome (arapaima density) in a subset of 39 communities to assess their influence. To understand regional patterns of institutional capacity for CBM, we evaluated the degree of presence of each principle in all 83 communities. The principle scores were positively related to arapaima density in the 39 CBM schemes, explaining about half of the variation. Design principles related to defined boundaries and graduated sanctions exerted the strongest influence on the capacity of CBM to increase arapaima density. The degree to which most principles were present in all 83 communities was generally low, however, with the two most influential principles (defined boundaries and graduated sanctions) being the least present of all. Although the roles of the other principles (management rules, conflict resolution, collective action, and monitoring systems) are probably important, our results indicate that efforts aimed at strengthening the presence of defined boundaries and graduated sanctions in communities hold promise to improve the effectiveness of arapaima CBM regionally. [ABSTRACT FROM AUTHOR]

Arapaima Arapaima gigas, also known as paiche and pirarucu, is a large South American freshwater fish with unique biology, favorable aquaculture characteristics, and potential for production in south Florida. This publication provides Arapaima gigas biology, specific culture methods known for each stage of development, and information about diseases and parasites, markets, and the laws associated with this species to potential Florida producers.

The arapaima is the largest of the extant air-breathing freshwater fishes. Their respiratory gas bladder is arguably the most striking of all the adaptations to living in the hypoxic waters of the Amazon basin, in which dissolved oxygen can reach 0 ppm (0 mg/l) at night. As obligatory air-breathers, arapaima have undergone extensive anatomical and physiological adaptations in almost every organ system. These changes were evaluated using magnetic resonance and computed tomography imaging, gross necropsy, and histology to create a comprehensive morphological assessment of this unique fish. Segmentation of advanced imaging data allowed for creation of anatomically accurate and quantitative 3D models of organs and their spatial relationships. The deflated gas bladder [1.96% body volume (BV)] runs the length of the coelomic cavity, and encompasses the kidneys (0.35% BV). It is compartmentalized by a highly vascularized webbing comprising of ediculae and inter-edicular septa lined with epithelium acting as a gas exchange surface analogous to a lung. Gills have reduced surface area, with severe blunting and broadening of the lamellae. The kidneys are not divided into separate regions, and have hematopoietic and excretory tissue interspersed throughout. The heart (0.21% BV) is encased in a thick layer of lipid rich tissue. Arapaima have an unusually large telencephalon (28.3% brain volume) for teleosts. The characteristics that allow arapaima to perfectly exploit their native environment also make them easy targets for overfishing. In addition, their habitat is at high risk from climate change and anthropogenic activities which are likely to result is fewer specimens living in the wild, or achieving their growth potential of up to 4.5 m in length.

The utilization of Amazonian fish skins, like paiche, to obtain leather, has been gaining importance in Peru. The beauty of the pattern of this fish skin comes from its light beige color and the black strip that runs through its back. This research aimed to develop a degreasing process for the tanning of paiche skin, that allows to preserve its natural pattern and color in the finished leather. For this purpose, a mixture of degreasers, diesel oil, lipases, and surfactants was used. In tanned skins, physical-mechanical properties, such as tear strength, tensile strength, elongation percentage, and shrinkage temperature, were evaluated. The presence of fishy smell in tanned paiche skins was evaluated through an analysis of fat content, fatty acid profiles, and sensorial tests. Besides, wastewater of the process was characterized to determine BOD5, COD, TSS, oils, and greases, TPH, phenols, and pH. This wastewater was treated by a laboratory-scale system, based on sedimentation, sifting, and flocculation-coagulation. As a result, a degreasing process using 8% of diesel oil, 18% of surfactants and 1.2% of lipidic enzymes, applied in cycles before and after the pickling process, was established. This process allowed the conservation of pattern and color of skin and the reduction of polyunsaturated fatty acids that cause the fishy smell in the leather, which complied with physicalmechanical standards for making footwear, bags, and clothing. Thus, a reduction in the pollutant charge in wastewater was achieved to acceptable environmental levels. [ABSTRACT FROM AUTHOR]

The arapaima is the largest of the extant air-breathing freshwater fishes. Their respiratory gas bladder is arguably the most striking of all the adaptations to living in the hypoxic waters of the Amazon basin, in which dissolved oxygen can reach 0 ppm (0 mg/l) at night. As obligatory air-breathers, arapaima have undergone extensive anatomical and physiological adaptations in almost every organ system. These changes were evaluated using magnetic resonance and computed tomography imaging, gross necropsy, and histology to create a comprehensive morphological assessment of this unique fish. Segmentation of advanced imaging data allowed for creation of anatomically accurate and quantitative 3D models of organs and their spatial relationships. The deflated gas bladder [1.96% body volume (BV)] runs the length of the coelomic cavity, and encompasses the kidneys (0.35% BV). It is compartmentalized by a highly vascularized webbing comprising of ediculae and inter-edicular septa lined with epithelium acting as a gas exchange surface analogous to a lung. Gills have reduced surface area, with severe blunting and broadening of the lamellae. The kidneys are not divided into separate regions, and have hematopoietic and excretory tissue interspersed throughout. The heart (0.21% BV) is encased in a thick layer of lipid rich tissue. Arapaima have an unusually large telencephalon (28.3% brain volume) for teleosts. The characteristics that allow arapaima to perfectly exploit their native environment also make them easy targets for overfishing. In addition, their habitat is at high risk from climate change and anthropogenic activities which are likely to result is fewer specimens living in the wild, or achieving their growth potential of up to 4.5 m in length. [ABSTRACT FROM AUTHOR]

Abstract Illegal wildlife trade is a lucrative business, which is driving many species towards extinction. Pangolins (Manis spp.) and arapaimas (Arapaima spp.) are two CITES listed genera coveted in the leather fashion industry for their unique skin pattern. The US has contributed to the decline of pangolin species and was historically a large market for pangolin leather products. While the US trade in pangolin products has declined since 2000, we suspect that pangolin leather may now be substituted by arapaima products. Arapaima leather trade has increased significantly since the year 2011. We found a strong positive correlation between the US states trading in both arapaima and pangolin leather products. The US states that were most involved in this trade had a lower population density and were comparatively wealthier than others. Leather items of both arapaima and pangolin were found for sale on eBay, with 75% of incidents in breach of eBay policy, and potentially illegal. Pangolin leather products were also falsely advertised as arapaima products. We conclude that arapaima leather is increasingly used to satisfy the persisting demand for exotic leather, and further research is urgently needed to determine the effect of the trade on wild arapaima populations.

This article explores the decision of a group of Amazonian lake fishermen to ban the use of nets to catch the pirarucu fish as part of an official agreement. It discusses the approach to artefacts found in the agentive turn and in recent explorations of Amazonian animism in Anthropology. It adopts the concept of technical object influenced by the anthropological approach to technology and in line with the ontogenetic perspective of Gilbert Simondon. The main focus is the way in which the fishermen compare the different modes of existence of the harpoon and the net. For them, the pirarucu net is a poor way to catch fish since it captures by itself, which is a form of cowardice in relation to the fish and drives them away. The ethnography centres on the operation of these objects and the way in which different properties of the fishermen and fish emerge through these processes. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the survival and growth of Arapaima gigas larvae reared in slightly salinized water. Pirarucu larvae (183.1 ± 41.2 mg and 3.4 ± 0.3 cm) were stocked in PVC tanks (20 L; n = 4; 40 larvae per tank) in a static system. A. gigas larvae were reared in increasing levels of salinized water (0, 1, 2, 3 and 4‰) for a period of 15 days. Fish were fed six times a day with Artemia nauplii (2,900 nauplii per larvae per meal in the beginning). The salinized water increased by at least four times the Artemia nauplii lifespan, which prolonged the time of live food supply to Arapaima larvae. Pirarucu larvae kept in freshwater presented the lowest values in weight gain, final weight and survival. Larvae reared in water with 4‰ of salinized water showed the highest final weight. Slightly salinized water enhances the growth and survival of A. gigas larvae and it can be a simple practice with low cost that can be applied in the routine of pirarucu larviculture. [ABSTRACT FROM AUTHOR]

Abstract An 8-week experiment (trial 1) was conducted to determine the optimal feeding frequency for juvenile Arapaima gigas. Seventy-two fish (500.0 ± 50.9 g, mean ± S.E) were randomly assigned to 12 tanks (500 l) in recirculating aquaculture systems (RAS). Four treatments with three replicates each were considered: T1) fish fed using self-feeders (free choice to eat); T2) fish fed by hand to apparent satiation twice daily (09:00 h, 17:00 h); T3) fish fed by hand to apparent satiation 3 times daily (09:00 h, 12:00 h, 17:00 h); T4) fish fed by hand at fixed rates (2% BW day-1) twice daily (9:00 and 17:00). After 60 days, growth parameters, biochemical indices in blood plasma and digestible enzyme activities were evaluated and water flow was closed to evaluate the effect of feeding strategies on total ammonia nitrogen (TAN) and phosphorous (P) accumulation. The results showed that growth parameters and body composition were not influenced by feeding strategies (p >.05). The biochemical analysis revealed no differences in glucose, cholesterol or aspartate aminotransferase (p >.05). However, alanine aminotransferase and alkaline phosphatase increased in the treatments with the lowest feeding frequency (twice daily – T2) p <.05. No differences in protease, amylase or lipase in intestine were found (p >.05). TAN excretion was lower in T1 (0.100 μg/ml) compared to T2 (p =.001). P excretion was low (0.470 g kg BW) in T1 fish compared to T2 (0.615, p =.011). In short, all the feeding strategies evaluated can be used without compromising arapaima growth. However, apparent satiety twice daily led to increased N and P excretion. Highlights • Arapaima can be fed efficiently with self-feeders, though there was no difference in growth parameters and body composition. • Alanine aminotransferase and alkaline phosphatase increased in fish fed under apparent satiation three times per day. • There were no significant differences in digestive enzymes in fish subjected to different feeding strategies. • Phosphorus and total nitrogen excretion was low in RAS system when fish was allowed to trigger the self-feeders. [ABSTRACT FROM AUTHOR]

Early‐life survival of Arapaima gigas is one of the main challenges of its farming. In this study, we described the morphological and histochemical development of the gastrointestinal tract of arapaima larvae. Larvae were collected from a pond when they started to swim to the water surface (initial day) and were housed in indoor tanks. Daily samplings (n = 10) were performed from 0 to the 11th day after the collection (DAC) and then on the 14th, 17th, and 20th DAC. On the initial day, arapaima larvae (0.05 ± 0.01 g; 2.21 ± 0.06 cm) had opened mouth and anus and no yolk sac. In addition, larvae presented well‐developed digestive organs. Gastric glands were fully formed, with positive reactions to alcian blue (AB) pH 1.0 as well as to periodic acid‐Schiff (PAS) in the simple columnar epithelium. There were folds throughout the intestine and brush border, with an AB pH of 2.5 + PAS positive mucins. From 1 to 11 DAC, larvae presented increasing concentrations of gastric glands and thickness of the stomach muscular layer. From 14 to 20 DAC, the intestine presented high‐fold complexity. We suggest that arapaima larvae may be fed exogenous inert diets at a size of around 2 cm. [ABSTRACT FROM AUTHOR]

Understanding the reproductive ecology of freshwater fishes is essential to minimize the losses in global freshwater biodiversity but is often limited in data‐poor regions, such as tropical floodplain ecosystems. Specifically, the study investigated whether size at first sexual maturation and nesting features for arapaima vary within and across regions in the floodplain of the Amazon River.Data were collected at several sites in the Lower Amazon with varying arapaima densities and fishing practices. Female gonads were examined from commercial catch to calculate total length of first sexual maturation (L50). Nest features were surveyed in the field. The size at first maturation and nest features (i.e. nest morphology, habitat, and density) were compared among sites with different population densities in the Lower Amazon and among estimates drawn from the literature for other regions.In the Lower Amazon, L50 showed significant variation between high‐density (139 cm) and other sites (~168 cm). Overall variation in L50 estimates for arapaima range from 139 cm in the Lower Amazon to 207 cm in the Upper Amazon in Peru. Nests in different regions show variation among certain nest features and a positive relationship between nest density and arapaima population density. In the Lower Amazon, 90% of nests were found under woody vegetation.The results show considerable diversity in size at first maturity and nesting features for arapaima. This suggests that there may be multiple evolutionarily significant units or species, even within the study area. This study also illustrates the importance of forest cover to arapaima spawning. Furthermore, different nesting morphologies were found at different sites. There are meaningful variations in arapaima reproductive behaviour, both locally and basin‐wide, that require further study as they have implications for effective management and conservation initiatives. [ABSTRACT FROM AUTHOR]

Background: Arapaima gigas (Schinz, 1822) is the largest freshwater scaled fish in the world, and an emerging species for tropical aquaculture development. Conservation of the species, and the expansion of aquaculture requires the development of genetic tools to study polymorphism, differentiation, and stock structure. This study aimed to investigate genomic polymorphism through ddRAD sequencing, in order to identify a panel of single nucleotide polymorphisms (SNPs) and to simultaneously assess genetic diversity and structure in wild (from rivers Amazon, Solimões, Tocantins and Araguaia) and captive populations. Results: Compared to many other teleosts, the degree of polymorphism in A. gigas was low with only 2.3% of identified RAD-tags (135 bases long) containing SNPs. A panel of 393 informative SNPs was identified and screened across the five populations. Higher genetic diversity indices (number of polymorphic loci and private alleles, Shannon's Index and HO) were found in populations from the Amazon and Solimões, intermediate levels in Tocantins and Captive, and very low levels in the Araguaia population. These results likely reflect larger population sizes from less urbanized environments in the Amazon basin compared to Araguaia. Populations were significantly differentiated with pairwise FST values ranging from 0.086 (Amazon × Solimões) to 0.556 (Amazon × Araguaia). Mean pairwise relatedness among individuals was significant in all populations (P < 0.01), reflecting a degree of inbreeding possibly due to severe depletion of natural stocks, the species sedentary behaviour and possible sampling biases. Although Mantel test was not significant (P = 0.104; R2 = 0.65), Bayesian analysis in STRUCTURE and discriminant analysis of principal components (DAPC) showed populations of Amazon and Solimões to be genetically differentiated from Araguaia, with Tocantins comprising individuals from both identified stocks. Conclusions: This relatively rapid genotyping by sequencing approach proved to be successful in delineating arapaima stocks. The approach and / or SNP panels identified should prove valuable for more detailed genetic studies of arapaima populations, including the elucidation of the genetic status of described discrete morphotypes and aid in delivery of conservation programs to maintain genetic diversity in reservoirs across the Amazon region. [ABSTRACT FROM AUTHOR]

Abstract The current study tested the efficacy of a dietary immunostimulant additive (Aquate Fish™®) on the growth performance, and on the physiological and immune responses of Arapaima gigas. Two trials were carried out: a feeding trial for 30 days with the experimental diets and a challenge trial for 7 days, in which fish were bacterial challenge (Aeromonas hydrophila) following by 60 s handling stress. During the feeding trial, fingerlings were fed diets supplemented with 0 (control), 6, 9 and 12 g Aquate Fish™®/kg diet. Dietary supplementation did not influence feed intake, feed conversion and condition factor, but increased the final biomass, number of erythrocytes, thrombocytes, leukocytes, lymphocytes, monocytes, hemoglobin, glucose, globulins and plasma triglycerides in fish fed at a concentration of 12 g/kg diet. After bacterial infection, mortality occurred only in fish fed control treatment, whereas respiratory burst of leukocytes, number of leukocytes and lymphocytes increased in fish that received 12 g of dietary supplementation. The results indicated that dietary supplementation with 12 g of Aquate Fish™® improved biomass and immunity performance of A. gigas fingerlings, without negatively affecting blood biochemical parameters. Highlights • Supplementation with Aquate Fish™ immunostimulant increases the biomass and blood parameters of Arapaima gigas. • Aquate Fish™ supplementation followed by challenge of bacterial infection not cause mortality in Arapaima gigas. • Dietary supplementation followed by bacterial infection increases respiratory burst and leukocytes and lymphocytes. • Dietary supplementation with Aquate Fish™ improves growth and immunity parameters of A. gigas. [ABSTRACT FROM AUTHOR]

The development of analytical tools to determine the origin of fish is useful to better understand patterns of habitat use and to monitor, manage and control fisheries, including certification of food origin. The application of isotopic procedures to study fish calcified structures (scales, vertebrae, and otoliths) may provide robust information about the fish geographic origin and environmental living conditions. In this study, we used Sr and C isotopic markers recorded in otoliths of wild and farmed commercialized pirarucu (Arapaima spp.) to evaluate their prediction potential to trace the fish origin. Wild and farm fish specimens, as well as food used for feeding pirarucu in captivity, were collected from different sites. Isotope analyses of otoliths performed by IRMS (δ13C) and LAfs-MC-ICPMS (87Sr/86Sr) were compared to the isotopic composition of water and of the food given to the fish in the farms. Wild fish specimens that lived in environments with the largest fluctuation of river water Sr isotope ratios over time presented the largest Sr isotope variations in otoliths. A quadratic discriminant analysis on otolith isotopic composition provided 58% of correct classification for fish production (wild and farmed) and 76% of correct classification for the fish region. Classification accuracy for region varied between 100% and 29% for the Madeira and the lower Amazon fishes, respectively. Overall, this preliminary trial is not yet fully satisfying to be applied as a commercial traceability tool. However, given the importance of Arapaima spp. for food security and the generation of economic resources for millions of people in the Amazon basin, further analyses are needed to increase the discrimination performance of these biogeographical tags. [ABSTRACT FROM AUTHOR]

Human modification of floodplain ecosystems is widespread and a major threat to fish populations, particularly in the tropics where fish diversity and rates of floodplain degradation are high. Identifying measures to minimize the susceptibility of floodplain fishes to habitat modification requires understanding dry‐season lake habitat selection for species of conservation concern.This study examined the effects of environmental factors on dry‐season floodplain lake habitat selection by arapaima (Arapaima spp.) and determined the extent to which they differed across three size classes. In floodplain lakes of the lower Amazon River, variables were measured at locations representing habitat availability and compared with measurements taken where arapaima were observed during surface breathing. Regression models were used to account for between‐lake variation in the presence of arapaima owing to nearby fishing communities. The probability of arapaima presence at each sample location was modelled based on the variables measured.The results indicated that arapaima expressed distinct habitat selection patterns, which differed significantly across size classes. The general pattern observed was that all arapaima were more likely to be found in deeper, more turbid, and higher conductivity locations, whereas smaller arapaima were more likely to remain near dense beds of floating macrophytes. The probability of arapaima presence differed among fishing community territories, reflecting differences in management schemes.Deeper, macrophyte‐rich sections of floodplain lakes appear to provide key habitats for arapaima and deserve consideration for becoming priority targets for conservation of the rich diversity of fish species in these systems. [ABSTRACT FROM AUTHOR]

Recreational fisheries are increasingly important sectors of tourism-based economies. In the last decade, new recreational fisheries have emerged that target species of varying conservation status including vulnerable, endangered, and unassessed species. In Guyana, catch-and-release angling tourism has begun to target arapaima, a genus of giant air-breathing fishes. Given the uncertain conservation status of this species and that no information is available to evaluate the sustainability of this activity, we sought to describe the responses of arapaima to recreational angling. We harnessed tri-axial accelerometer biologgers around the trunk of fish that had been captured and released by recreational anglers, allowing us to monitor post-release survival and behaviour, including surfacing, which is essential for this air-breathing fish to recover from exhaustion. Twenty-seven individuals were instrumented (162 ± 25 cm), 24 of which were considered survivors (89%) during the 47 ± 35 (SD) min monitoring period. Fish that died were observed to drown soon after release (i.e. within minutes), not surfacing to breathe air. Supervised machine learning classification of behaviours using a random forest algorithm identified surfacing events with 80% accuracy (i.e. out-of-bag error rate = 20%), which we applied to unobserved data periods to estimate breathing frequency after release, along with overall dynamic body acceleration (ODBA) as a proxy for activity. Neither mean breathing frequency nor ODBA were related to body size (total length), handling time (which incorporated facilitated recovery of individuals), nor time of capture (early or late in the dry season spanning water temperatures of 29.3–34.1 °C). The precise angling-related factors that led to arapaima mortality were unclear, but the frequency of mortality aligns with the mortality documented in other recreational fisheries. This mortality source can be incorporated into conservation plans and provide context to the impacts of recreational angling relative to the costs of legal or illegal harvest. [ABSTRACT FROM AUTHOR]

The community‐based management of Arapaima gigas for sustainable commercial use allows that wild fish legally harvested in the Brazilian Amazon supply the demand for exotic leather in the US, supporting the conservation of the forest and providing income for fishers communities if based in fair‐trade. We provide a more optimistic view than Heinrich et al. (2019) on the effects of international trade of arapaima leather in the conservation of the species in Brazil. [ABSTRACT FROM AUTHOR]

Background: The Arapaima (Arapaima gigas) is one of the world's largest freshwater bony fish, and is found in the rivers of the Amazon basin. This species is a potential aquaculture resource, although reproductive management in captivity is limited in particular due to the lack of external sexual dimorphism. In this study, using the 454 Roche platform (pyrosequencing) techniques, we evaluated a major portion of the transcriptome of this important Amazonian species. Results: Four libraries obtained from the liver and skin tissue of juvenile specimens (representing males and females separately) were sequenced, yielding 5,453,919 high-quality reads. The de novo transcriptome assembly resulted in 175,792 contigs, with 51,057 significant blast hits. A total of 38,586 transcripts were mapped by Gene Ontology using Blast2GO. We identified 20,219 genes in the total transcriptome (9,551 in the liver and 16,818 in the skin). The gene expression analyses indicated 105 genes in the liver and 204 in the skin with differentiated expression profiles, with 95 being over-expressed in the females and 214 in the males. The log2 Fold Change and heatmap based on Reads Per Kilobase per Million mapped reads (RPKM) revealed that the gene expression in the skin is highly differentiated between male and female arapaima, while the levels of expression in the liver are similar between the sexes. Conclusion: Transcriptome analysis based on pyrosequencing proved to be a reliable tool for the identification of genes with differentiated expression profiles between male and female arapaima. These results provide useful insights into the molecular pathways of sexual dimorphism in this important Amazonian species, and for comparative analyses with other teleosts. [ABSTRACT FROM AUTHOR]

The Pirarucu (Arapaima gigas) is one of the world's largest freshwater fishes and member of the superorder Osteoglossomorpha (bonytongues), one of the oldest lineages of ray-finned fishes. This species is an obligate air-breather found in the basin of the Amazon River with an attractive potential for aquaculture. Its phylogenetic position among bony fishes makes the Pirarucu a relevant subject for evolutionary studies of early teleost diversification. Here, we present, for the first time, a draft genome version of the A. gigas genome, providing useful information for further functional and evolutionary studies. The A. gigas genome was assembled with 103-Gb raw reads sequenced in an Illumina platform. The final draft genome assembly was ∼661 Mb, with a contig N50 equal to 51.23 kb and scaffold N50 of 668 kb. Repeat sequences accounted for 21.69% of the whole genome, and a total of 24,655 protein-coding genes were predicted from the genome assembly, with an average of nine exons per gene. Phylogenomic analysis based on 24 fish species supported the postulation that Osteoglossomorpha and Elopomorpha (eels, tarpons, and bonefishes) are sister groups, both forming a sister lineage with respect to Clupeocephala (remaining teleosts). Divergence time estimations suggested that Osteoglossomorpha and Elopomorpha lineages emerged independently in a period of ∼30 Myr in the Jurassic. The draft genome of A. gigas provides a valuable genetic resource for further investigations of evolutionary studies and may also offer a valuable data for economic applications. [ABSTRACT FROM AUTHOR]

The nematode Hysterothylacium sp. (Nematoda, Anisakidae) may cause significant economic losses in fish production. In order to control the nematode larvae in juvenile pirarucu (52 ± 3.2 g), the efficacy of essential oil (EO) of Piper aduncum when added to feed was evaluated. Chemical analysis of the EO composition had been performed previously, showing that 92% of the substance was dillapiole. After the palatability test, the efficacy of the EO was evaluated (0, 32, 48, 56, and 64 mL/kg) at 7 and 15 days, based on the blood parameters and the parasite load of the fish. The results showed significant differences for hematocrit and corpuscular constants at 7 days and for total proteins at 15 days between the treatment groups and the control group (without EO). The parasitic indices showed a prevalence of 100% for stage L3 larva of the nematode Hysterothylacium sp. At 7 and 15 days, the values of average intensity, average abundance, and intensity of parasites decreased with increasing EO concentration, and at 15 days, these were significantly lower between the treatment group and the control group, with an efficacy of 76.21% for 64 mL/kg. Thus, the EO of P. aduncum demonstrates anthelmintic potential in the control of nematode larvae in pirarucu without affecting fish homeostasis. [ABSTRACT FROM AUTHOR]

Abstract: As Arapaima gigas is one of the most valuable species for the growing production of Amazonian aquaculture, knowledge of its reproductive behaviour and its application to increase reproduction success in captivity is of great importance as no hormonal spawning induction technique exists for this species. An acoustic positioning system (LOTEK Inc.) was used to observe the interactions of adult fish to better understand the formation of mating pairs. Fish were placed in a 4,500 m2 aquaculture pond over a 6‐month period in the IIAP field station of Pucallpa, Perú. This paper describes the methodological protocols used to set up and test the hydrophone array and presents the methodology used for the analysis of the huge amount of collected data. This methodology is illustrated by the analysis of a 6‐day period for a mating pair that showed a spawning event. The results indicated that male and female occupied mostly one preferential area in one pond edge where the nesting area is located. Different activity patterns were observed during the spawning event, with male and female being closer during the spawning day. The results also showed that male travelled less distance than female during the studied period. Finally these results demonstrated the suitability of such equipment to monitor fish interactions at fine spatial (sub meter) and temporal (5 s) scales in confined environments like aquaculture ponds. [ABSTRACT FROM AUTHOR]

Abstract: The South American continent is known for its high production and exports in fisheries and aquaculture, but has not reached its full potential in fish farming. The latest data on fish production in Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Uruguay and Venezuela were explored in this review. Aspects of biology, production, market and health of the species most produced in South America are described in detail. These species include the round fish (Colossoma spp., Piaractus spp. and hybrids) and catfish (Pseudoplatystoma spp. and hybrids), in addition to the promising pirarucu Arapaima gigas, yellowtail tetra Astyanax altiparanae and silver catfish Rhamdia quelen. Among the countries mentioned, Chile and Brazil are two of the largest intensive fish producers in the world. Chile relies primarily on marine fish, whereas Brazil is prominent for continental production. Special emphasis is given to the black pacu Colossoma macropomum because it is a commonly farmed fish in South American countries and offers several desirable productive characteristics (domesticated, omnivorous and easy to reproduce). Furthermore, this fish has the greatest potential to compete economically with tilapia production in South America. The production of native fish is currently overtaking the production of exotic species in some countries, which is considered a milestone for South American aquaculture. Regarding diseases, the main pathogens are similar to those observed throughout the world, such as Ichthyophthirius multifiliis, different species of monogeneans and trichodinids, and the bacteria Aeromonas hydrophila. Local pathogens, such as the parasites Perulernaea gamitanae and Goezia spinulosa, are also concerning. [ABSTRACT FROM AUTHOR]

Abstract: In carnivorous fish species, zooplankton is one of the main food items in the early life stages and some fish species continue feeding on such food items further along the life stages even in the farming environment. In this study, the intake of natural food items was assessed in juvenile pirarucu Arapaima gigas reared in earthen ponds. Juvenile pirarucu (12.2 ± 4.32 g and 12.1 ± 1.13 cm) were stocked in fertilized earthen ponds (240 m²). For the analysis of the fish stomach content and plankton in the pond water, the fish and pond water were sampled weekly for 75 days and biweekly until the fish reached a mean weight of 750 g. Although artificial feed was used, pirarucu also ingested the natural food available in the pond water. Among the zooplankton, pirarucu demonstrated feeding preference for cladocerans despite the abundance of rotifers and copepods. Cladocerans were present in more than 80% of the stomach contents of fish up to 300 g and in 65%, 45% and 17% of fish of 301–500 g, 501–700 g and 701–900 g respectively. Copepods were present only in fish up to 500 g at low abundance. High ingestion of insects and plant material was observed in the stomach content of fish of all size classes. The results demonstrate that juvenile pirarucu ingest natural food available in the farming pond and suggests that the adoption of pond fertilization practices may have positive effects on fish growth performance. [ABSTRACT FROM AUTHOR]

This study was carried out to evaluate morphometry and direct and indirect effects of measurements and morphometric relationships on the weight of pirarucu body components. A total of 96 fish were raised in captivity at the Federal University of Rondônia, Presidente Médici - RO, Brazil, with a mean body weight of 9.18 ± 0.1 kg and 104 ± 0.3 cm in length. After desensitizing, the fish were sacrificed, weighed and morphometric measurements of total (TL), standard (SL), head (HL), trunk (LA) and tail (CL) lengths and frontal perimeter (FP), larger perimeter (LP) and tail perimeter (CP) were determined. The fish were dissected and the following body components were measured: leather (with scales), head, viscera and carcass divided into meat layer and spines. The data were submitted to descriptive and multiple regression analyses and the correlation coefficients were separated into direct and indirect effects by a path analysis. Most of the measurements and morphometric ratios showed significant correlations with body weights and body components (carcass, head, meat layer, leather, viscera and spines). LP showed a greater direct and positive effect and was determinant for the variation of total weight and meat layer weight. [ABSTRACT FROM AUTHOR]

Abstract: The loading density of pirarucu Arapaima gigas transported for 6 hr in open system was assessed on survival, physiological parameters (blood hematocrit, cortisol, lactate and glucose concentrations) and water quality (temperature, pH, ammonia, dissolved oxygen and carbon dioxide). No mortality was observed after fish transportation at 80, 120 and 160 kg/m³, although ammonia and carbon dioxide concentrations increased and dissolved oxygen decreased. Physiological parameters were not affected by loading density but significant differences were observed between sampling periods (immediately before transport, immediately after transport, 24 and 96 hr after transport), except glucose. Hematocrit values increased with time, whereas lactate concentration decreased. No significant differences were observed in blood cortisol levels before and after transport, but concentration increased gradually for 96 hr after transport. According to the results, 9 kg pirarucu may be transported for up to 6 hr at a loading density of 160 kg/m³. [ABSTRACT FROM AUTHOR]

Fish scales serve as a flexible natural armor that have received increasing attention across the materials community. Most efforts in this area have focused on the composite structure of the predominately organic elasmodine, and limited work addresses the highly mineralized external portion known as the Limiting Layer (LL). This coating serves as the first barrier to external threats and plays an important role in resisting puncture. In this investigation the structure, composition and mechanical behavior of the LL were explored for three different fish, including the arapaima ( Arapaima gigas ), the tarpon ( Megalops atlanticus ) and the carp ( Cyprinus carpio ). The scales of these three fish have received the most attention within the materials community. Features of the LL were evaluated with respect to anatomical position to distinguish site-specific functional differences. Results show that there are significant differences in the surface morphology of the LL from posterior and anterior regions in the scales, and between the three fish species. The calcium to phosphorus ratio and the mineral to collagen ratios of the LL are not equivalent among the three fish. Results from nanoindentation showed that the LL of tarpon scales is the hardest, followed by the carp and the arapaima and the differences in hardness are related to the apatite structure, possibly induced by the growth rate and environment of each fish. Statement of Significance The natural armor of fish, turtles and other animals, has become a topic of substantial scientific interest. The majority of investigations have focused on the more highly organic layer known as the elasmodine. The present study addresses the highly mineralized external portion known as the Limiting Layer (LL). Specifically, the structure, composition and mechanical behavior of the LL were explored for three different fish, including the arapaima (Arapaima gigas), the tarpon (Megalops atlanticus) and the carp (Cyprinus carpio). Results show that there are significant differences in the surface morphology of the LL from posterior and anterior regions in the scales, and between the three species. In addition, the composition of the LL is also unique among the three fish. Results from nanoindentation showed that the LL of tarpon scales is the hardest, followed by the carp and the arapaima and the differences in hardness are related to the apatite structure, possibly induced by the growth rate and environment of each fish. In addition, a new feature was indentified in the LL, which has not been discussed before. As such, we feel this work is unique and makes a significant contribution to the field. [ABSTRACT FROM AUTHOR]

The effect of Ultraviolet radiation type C (UV-C) radiation (0.100 ± 0.010 J/cm2) on shelf life ofArapaima gigasfillets stored at 4 ± 1°C for 18 days was investigated. The samples were analyzed for total aerobic mesophilic bacteria (TAMB) counts; total aerobic psychrotrophic bacteria (TAPB) counts; Enterobacteriaceae; purge loss; pH; lipid oxidation; total volatile bases (TVB-N); ammonia; biogenic amines (BAs); andL , a , andb values. UV-C radiation increased (P < 0.05) the generation time of all bacterial groups evaluated, increasing the shelf life by 2 days. UV-C-treated fillets showed lower (P < 0.05)L values, purge loss, pH, TVB-N, ammonia, and BAs levels than their control counterparts throughout the storage period. Moreover, UV-C treatment did not result (P > 0.05) in detrimental effects on lipid oxidation ora andb values. UV-C at 0.100 J/cm2demonstrated a good potential for use inA. gigasfillets and, therefore, it could be applied at industrial scale. [ABSTRACT FROM AUTHOR]

Neotropical floodplains are usually productive systems that are maintained by the nutrient, detritus and sediment inputs provided by the main river channel flood pulse. Ria lakes represent a special feature and habitat in the Amazonian floodplains, being characterised by a dendritic morphology and dependence on terrestrial inputs provided by an intricate stream network. Our objective was to evaluate the trophic ecology of the arapaima ( Arapaima sp.). We combined stomach content analysis with measurements of carbon and nitrogen stable isotope values from dorsal muscle to infer the ontogenetic changes in trophic level and isotopic niche width in floodplain and ria lakes. Arapaima diet was dominated by fish from low trophic positions. While most of the stomachs sampled in the study ria lake were full, empty stomachs predominated in samples taken in the floodplain lakes. These differences indicate that ria lakes may provide better feeding grounds for arapaima during the dry season, presumably because ria lakes are interconnected with a large stream network and the main river channel year round. Nitrogen stable isotope results further indicated an ontogenetic dietary shift in arapaima, with piscivory increasing as a function of length in both environments. Carbon stable isotope analysis indicated that energy sources used by arapaima varied by environment, with arapaima using a greater diversity of food sources in ria lakes than in floodplain lakes. Information about the main carbon sources is useful for fishery management because stakeholders may choose to conserve key vegetal groups to ensure the productivity and diversity of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Within the production chain of the Arapaima gigas (pirarucu), sanitary issues are still faced at the fingerling phase regarding infestations by the monogenean Dawestrema cycloancistrium . The present study had the objectives of describing the morphology and development phases of this parasite’s eggs and oncomiracidia and determining the hatching time and lifespan of the oncomiracidia at different temperatures. D. cycloancistrium eggs were oval and elongated and had a single long appendage at one pole. The egg development was divided into four phases: embryonated egg, developing egg, larva appearance and ecloded egg. They were found in four forms: isolated in gill filaments; grouped in clusters that were anchored in a gill filament; grouped in clusters and entangled in part of a dead adult monogenean; and grouped in clusters in the environment, fixed to a substrate. Eclosion occurred after 72–96 h, with faster development at 29 °C and 32 °C than at 24 °C. The morphology of the oncomiracidia were rounded and elongated. They had two pairs of pigmented eye-spots as well as two ciliated areas located on each lateral part of the body and another on the anterior part of the body. The lifespan of the D. cycloancistrium oncomiracidia were 50 and 58 h at 24 °C and 27 °C, respectively. Larvae were found in the mucus, indicating that the oncomiracidia penetrated the host integument. Understanding reproductive aspects of the D. cycloancistrium monogenean is important for developing specific prophylactic management strategies in aquaculture and providing valuable data for further studies. [ABSTRACT FROM AUTHOR]

Aims The aim of this study was to determine the intestinal microbiota of pirarucu ( Arapaima gigas) in different growth stages (adult and fingerlings) and to isolate and identify potential probiotic bacteria. Methods and Results High-throughput sequencing analysis of the intestinal contents revealed that the majority of sequences belonged to the Proteobacteria, Fusobacteria and Firmicutes phyla. At the genus level, the greatest number of sequences belonged to Bradyrhizobium in adult fish, while Cetobacterium was the most abundant in juvenile fish. Twenty-three lactic-acid bacteria ( LABs) were isolated on MRS agar from healthy juvenile fish. The isolates were tested in vitro for probiotic properties. Two isolates (identified as strains of Lactococcus lactis subsp. lactis and Enterococcus faecium) displayed antagonism against all 10 pathogens tested, were nonhaemolytic and maintained good viability for at least 3 weeks when supplemented to fish diets. The presence of a number of antibiotic resistance genes ( ARGs), conferring resistance to erythromycin, tetracycline and chloramphenicol, was investigated by PCR. Conclusions The absence of ARGs investigated the potential to antagonize pathogens, and favourable growth and survival characteristics indicate that these autochthonous isolates have the potential to be considered probiotics, which will be studied in future in vivo experiments. Significance and Impact of the Study This study has demonstrated, for the first time, the normal microbiota in the A. gigas intestine during different life stages and the presence of LAB strains. It also demonstrated LAB antibiotic resistance and antagonistic behaviour against pathogens isolated from the same fish. [ABSTRACT FROM AUTHOR]

Parental investment in Arapaima gigas includes nest building and guarding, followed by a care provision when a cephalic fluid is released from the parents’ head to the offspring. This fluid has presumably important functions for the offspring but so far its composition has not been characterised. In this study the proteome and peptidome of the cephalic secretion was studied in parental and non-parental fish using capillary electrophoresis coupled to mass spectrometry (CE-MS) and GeLC-MS/MS analyses. Multiple comparisons revealed 28 peptides were significantly different between males and parental males (PC-males), 126 between females and parental females (PC-females), 51 between males and females and 9 between PC-males and PC-females. Identification revealed peptides were produced in the inner ear (pcdh15b), eyes (tetraspanin and ppp2r3a), central nervous system (otud4, ribeye a, tjp1b and syn1) among others. A total of 422 proteins were also identified and gene ontology analysis revealed 28 secreted extracellular proteins. From these, 2 hormones (prolactin and stanniocalcin) and 12 proteins associated to immunological processes (serotransferrin, α-1-antitrypsin homolog, apolipoprotein A-I, and others) were identified. This study provides novel biochemical data on the lateral line fluid which will enable future hypotheses-driven experiments to better understand the physiological roles of the lateral line in chemical communication. [ABSTRACT FROM AUTHOR]

The arapaima, Arapaima gigas, is a fish whose populations are threatened by both overfishing and the ongoing destruction of its natural habitats. In the Amazon basin, varying levels of population structure have been found in A. gigas, although no data are available on the genetic diversity or structure of the populations found in the Araguaia-Tocantins basin, which has a topographic profile, hydrological regime, and history of fishing quite distinct from those of the Amazon. In this context, microsatellite markers were used to assess the genetic diversity and connectivity of five wild A. gigas populations in the Araguaia-Tocantins basin. The results of the analysis indicated low levels of genetic diversity in comparison with other A. gigas populations, studied in the Amazon basin. The AMOVA revealed that the Arapaima populations of the Araguaia- Tocantins basin are structured significantly. No correlation was found between pairwise FST values and the geographical distance among populations. The low level of genetic variability and the evidence of restricted gene flow may both be accounted for by overfishing, as well as the other human impacts that these populations have been exposed to over the years. The genetic fragility of these populations demands attention, given that future environmental changes (natural or otherwise) may further reduce these indices and eventually endanger these populations. The results of this study emphasize the need to take the genetic differences among the study populations into account when planning management measures and conservation strategies for the arapaima stocks of the Araguaia-Tocantins basin. [ABSTRACT FROM AUTHOR]

This study evaluated the in vitro and in vivo antiparasitic efficacy of formalin against Dawestrema cycloancistrium , the effects on the physiological response of Arapaima gigas and the residual action on fish muscle after 96 h of exposure. As regards the in vitro assay, 0, 22, 44, 66, 88, 110, 330, 660 and 880 mg L − 1 formalin were tested. After 1 h of exposure to 660 and 880 mg L − 1 formalin, there was a 100% mortality of D. cycloancistrium as well as after 2 h of exposure at 330 and 110 mg L − 1 and 3 h of exposure at 44, 66 and 88 mg L − 1 . Concerning the in vivo test, when fish were exposed to formalin at 0, 220, 330, 440 and 550 mg L − 1 , there was 100% survival at all concentrations and exposure times evaluated. Baths of 1 h with 440 and 550 mg L − 1 formalin showed 93.3% and 99.3% efficacy respectively. However, the baths of 12 h with 55 and 66 mg L − 1 formalin had the efficacy of 44.5% and 55.5% respectively. In 1 h baths with 220, 330, 440 and 550 mg L − 1 formalin, hematocrit, hemoglobin, number of total erythrocytes, mean corpuscular volume, mean corpuscular hemoglobin concentration, mean corpuscular hemoglobin, plasma glucose levels, cortisol, total proteins, chloride, calcium, sodium, potassium and magnesium of the fish presented no differences in relation to the control values. However, in baths of 12 h with 33, 44, 55 and 66 mg L − 1 formalin, there was a decrease in hematocrit, plasma levels of calcium and chloride, and increased levels of glucose and cortisol, depending on the concentration of formalin used. In the fish muscle, the formalin residue decreased after 96 h in all concentrations and periods evaluated, returning to values close to the control ones. The results indicate that formalin had its efficacy successfully proved in the treatment against D. cycloancistrium at higher concentrations such as 440 and 550 mg L − 1 formalin and shorter exposure time (1 h) without compromising fish homeostasis and consumer food safety. Statement of relevance The manuscript represents original research on use of formalin in vitro and in vivo for treating infection by monogenoidean Dawestrema cycloancistrium in Arapaima gigas , the giant fish from Amazon. In the fish, muscle the residue levels of formalin after exposure was also investigated. Formalin have efficacy in the treatment against D. cycloancistrium at higher concentrations (440 and 550 mg.L − 1 ) of formalin and shorter exposure time (1 h) and without compromising A. gigas homeostasis and consumer food safety. [ABSTRACT FROM AUTHOR]

The present study describes the morphology and histology of the digestive tract of juvenile pirarucu, which is a Neotropical fish species with great potential for aquaculture in the Amazon region. Three size classes of pirarucu juveniles from commercial fish farms were sampled for histological examination of the oesophagus, stomach, pyloric caeca, intestine and liver. The morphological and histological features of the pirarucu digestive tract are similar to other carnivorous teleosts and enable the species to ingest, store and digest large food items. Acidic and neutral mucins are secreted by the mucosa of the oesophagus, stomach, pyloric caeca and intestine to protect the mucosal epithelium and to lubricate and facilitate food passage along the digestive tract. Complex transverse folds are predominant in the intestinal mucosa and most likely contribute to optimization of the digestion and nutrient absorption processes, thereby offsetting the relatively short length of the intestine. The exocrine pancreas appears diffuse in the liver and mesentery around the pyloric region of the stomach, pyloric caeca and initial part of the intestine. The digestive tract morphology and thickness become increasingly developed with the size of pirarucu. [ABSTRACT FROM AUTHOR]

We compare the characteristics of the armored scales of three large fish, namely the Arapaima gigas (arapaima), Latimeria chalumnae (coelacanth), and Atractosteus spatula (alligator gar), with specific focus on their unique structure-mechanical property relationships and their specialized ability to provide protection from predatory pressures, with the ultimate goal of providing bio-inspiration for manmade materials. The arapaima has flexible and overlapping cycloid scales which consist of a tough Bouligand -type arrangement of collagen layers in the base and a hard external mineralized surface, protecting it from piranha, a predator with extremely sharp teeth. The coelacanth has overlapping elasmoid scales that consist of adjacent Bouligand -type pairs, forming a double-twisted Bouligand -type structure. The collagenous layers are connected by collagen fibril struts which significantly contribute to the energy dissipation, so that the scales have the capability to defend from predators such as sharks. The alligator gar has inflexible articulating ganoid scales made of a hard and highly mineralized enamel-like outer surface and a tough dentine-like bony base, which resist powerful bite forces of self-predation and attack by alligators. The structural differences between the three scales correspond with the attack of their predators, and show refined mechanisms which may be imitated and incorporated into superior bioinspired and biomimetic designs that are specialized to resist specific modes of predation. [ABSTRACT FROM AUTHOR]

The common gonadotrophic hormone α-subunit (GTHα) has been previously isolated by our research group from A. gigas pituitaries; in the present work the cDNA sequences encoding FSHβ and LHβ subunits have also been isolated from the same species of fish. The FSH β-subunit consists of 126 amino acids with a putative 18 amino acid signal peptide and a 108 amino acid mature peptide, while the LH β-subunit consists of 141 amino acids with a putative 24 amino acid amino acid signal peptide and a 117 amino acid mature peptide. The highest identity, based on the amino acid sequences, was found with the order of Anguilliformes (61%) for FSHβ and of Cypriniformes (76%) for LHβ, followed by Siluriformes, 53% for FSHβ and 75% for LHβ. Interestingly, the identity with the corresponding human amino acid sequences was still remarkable: 45.1% for FSHβ and 51.4% for LHβ. Three dimensional models of ag-FSH and ag-LH, generated by using the crystal structures of h-FSH and h-LH as the respective templates and carried out via comparative modeling and molecular dynamics simulations, suggested the presence of the so-called “seat-belt”, favored by a disulfide bond formed between the 3rd and 12th cysteine in both β-subunits. The sequences found will be used for the biotechnological synthesis of A. gigas gonadotrophic hormones (ag-FSH and ag-LH). In a first approach, to ascertain that the cloned transcripts allow the expression of the heterodimeric hormones, ag-FSH has been synthesized in human embryonic kidney 293 (HEK293) cells, preliminarily purified and characterized. [ABSTRACT FROM AUTHOR]

Arapaima gigas , a fish with a high market value, has been farmed in different localities within Brazil. Among its parasites, adults of Goezia spinulosa are reported to cause ulcers in the stomach and to result in the death of farmed fingerlings. Due to the veterinary importance of this nematode in cultured arapaimas, an integrative taxonomic study is proposed, combining morphological, ultrastructural and genetic profiles of this parasite. The fish were obtained from semi-intensive fish farming in Acre State, Brazil. The fish measured 7–42 cm in total length and the intensity of infection was 1–60 parasites per fish. The site of infection was mainly the stomach. Morphological and ultrastructural analyses of G. spinulosa showed the importance of its spiny body in firmly attaching the worm to the gastric mucosa, resulting in lesions, ulcers and deep gastric perforations of the stomach wall. New sequences for partial 18S rDNA, ITS1, 5.8S and ITS2 rDNA, partial 28S rDNA, cox1 mtDNA and for cox2 mtDNA are presented. Phylogenetic reconstructions based on the partial 18S and 28S rDNA shows species of Goezia occur in a clade well separated from other genera in both analyses. Both the partial 18S and 28S rDNA genes represented good genetic markers for distinguishing genera of the Raphidascarididae, with exception of Hysterothylacium . This integrated taxonomic study produced a robust profile for G. spinulosa that will aid the diagnosis of both adults and larval stages from arapaimas and possible intermediate hosts. [ABSTRACT FROM AUTHOR]

Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The goal of this study was to evaluate the effects of modified atmosphere in packing sous vide of pirarucu in tucupi and shrimp sauce under refrigeration. Three treatments were carried out vacuum at 98%, 60%CO 2 /40%N 2 , and 70%CO 2 /30%N 2 . The composition of CO 2 and N 2 was monitored along with evaluation of pH, a w , water retention capacity, acidity, texture, N-TVB and TBARS, color, mesophilic and psychotropic anaerobes, presence of Salmonella spp, sulphite-reducing Clostridia, counts of coagulase-positive Staphylococci, coliforms at 45 °C and sensorial analysis. All results were compared through ANOVA, Tukey's test, Principal Component Analysis and Multiple Factor Analysis. We observed a trend towards the reduction of CO 2 in packages while O 2 has increased by the end of storage. The microbiological results were within the established limits by law during the entire period. The shelf life of sous vide stored could be defined by N-TVB, TBARS, b* and C*, general acceptance, texture and flavor in 49 days of storage. Industrial relevance The development of sous vide with freshwater fish is an alternative for a value-added product to be supplied to market niches. Employing the sous vide technique on fish yields a product with better color, taste, texture, and nutrient retention than the traditional cooking processes, which makes it an attractive alternative for its consumption. This study aimed to prepare sous vide using captive pirarucu, tucupi and shrimp and to analyze the microbiological, physicochemical and sensory quality parameters during refrigerated in atmosphere modified packaging storage. The results of this study establish the product's shelf life (49 days) and contribute to defining processing and storage conditions for fish sous vide . [ABSTRACT FROM AUTHOR]

The Brazilian teleost Arapaima gigas is an iconic species of the Amazon. In recent years a significant effort has been put into the farming of arapaima to mitigate overfishing threats. However, little is known regarding the nutritional requirements of A. gigas in particular those for essential fatty acids including the long-chain polyunsaturated fatty acids (LC-PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The ability to biosynthesize LC-PUFA is dependent upon the gene repertoire of fatty acyl desaturases (Fads) and elongases (Elovl), as well as their fatty acid specificities. In the present study we characterized both molecularly and functionally an orthologue of the desaturase fatty acid desaturase 2 ( fads2 ) from A. gigas . The isolated sequence displayed the typical desaturase features, a cytochrome b 5 -domain with the heme-binding motif, two transmembrane domains and three histidine-rich regions. Functional characterization of A. gigas fads2 showed that, similar to other teleosts, the A. gigas fads2 exhibited a predominant Δ6 activity complemented with some capacity for Δ8 desaturation. Given that A. gigas belongs to one of the oldest teleostei lineages, the Osteoglossomorpha, these findings offer a significant insight into the evolution LC-PUFA biosynthesis in teleosts. [ABSTRACT FROM AUTHOR]

Daily feeding rhythms and the ability of pirarucu ( Arapaima gigas ) to compose a balanced diet through macronutrient self-selection were evaluated. Twelve fish (1573.3 ± 74.4 g) were distributed in six tanks of 250 l, two fish per tank. First, three experimental diets were prepared using an incomplete mixture of macronutrients (75%protein/25%carbohydrate-PC, 75%protein/25%fat-PF and 10% protein/45%fat/45%carbohydrate-PFC). These diets were provided to fish through a self-feeding system connected to a computer to record feeding activity. After this procedure, fish were challenged with a 50% protein dilution (diets: PC50 and PF50). The results showed that pirarucu exhibited a strict diurnal feeding pattern with 95.4% of daily feeding activity observed in the daytime. Fish selected 56.3% P, 24.2% C, 19.5% F, and consumed 150–151 kJ/kg BW/day of energy. After protein dilution, fish sustained energy intake by increasing the consumption of PC50 and PF50 to maintain the target protein intake of the previous stage. When fish were protein-restricted, they failed to sustain previous energy intake. These findings can be used to design feeding regimes and for formulating aquafeed for pirarucu. Statement of relevance The use of an automatic feeder system activated by the fish could allow the animal to feed at their preferred time and hence reduces waste and improve the intake. Studies that consider the fish preference as a guide in designing diets can provide data on mechanisms of nutrient intake regulation for the development of aquafeeds for new species with potential for aquaculture. [ABSTRACT FROM AUTHOR]