A duplicated copy of id2b is an unusual sex-determining candidate gene on the Y chromosome of arapaima (Arapaima gigas)

Arapaima gigas is one of the largest freshwater fish species of high ecological and economic importance. Overfishing and habitat destruction are severe threats to the remaining wild populations. By incorporating a chromosomal Hi-C contact map, we improved the arapaima genome assembly to chromosome-level, revealing an unexpected high degree of chromosome rearrangements during evolution of the bonytongues (Osteoglossiformes). Combining this new assembly with pool-sequencing of male and female genomes, we identified id2bbY, a duplicated copy of the inhibitor of DNA binding 2b (id2b) gene on the Y chromosome as candidate male sex-determining gene. A PCR-test for id2bbY was developed, demonstrating that this gene is a reliable male-specific marker for genotyping. Expression analyses showed that this gene is expressed in juvenile male gonads. Its paralog, id2ba, exhibits a male-biased expression in immature gonads. Transcriptome analyses and protein structure predictions confirm id2bbY as a prime candidate for the master sex-determiner. Acting through the TGFβ signaling pathway, id2bbY from arapaima would provide the first evidence for a link of this family of transcriptional regulators to sex determination. Our study broadens our current understanding about the evolution of sex determination genetic networks and provide a tool for improving arapaima aquaculture for commercial and conservation purposes.

Candidate Species for Florida Aquaculture: Arapaima Arapaima gigas

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.

Avaliação da composição físico-química do concentrado proteico e farinhas liofilizadas obtidos a partir de resíduos do pirarucu (Arapaima gigas)

O pirarucu (Arapaima gigas) é considerado um dos maiores peixes de água doce do mundo. Porém o seu beneficiamento gera grandes quantidades de resíduos que podem agregar valor no desenvolvimento de novos produtos, gerar renda à população local e ainda possibilidade da difusão do seu consumo. Dentre os métodos de desidratação existentes, a liofilização se destaca por promover uma maior preservação das características sensoriais e nutricionais dos alimentos. Os concentrados proteicos provenientes de pescado são produtos obtidos por desidratação que possuem alto conteúdo de proteínas. Suas características primordiais são o alto valor biológico, baixo custo e fácil conservação. O objetivo desse trabalho foi avaliar a composição físico-química do concentrado proteico e farinha liofilizada de resíduos do pirarucu. A obtenção do concentrado proteico se deu através da modificação de uma metodologia já existente, com alterações nas etapas de desodorização e deslipidificação. E a liofilização através de um liofilizador de bancada. Nos dois métodos utilizou-se a cabeça e a carcaça do Pirarucu, separadamente, a fim de verificar se existiam diferenças significativas (p ≤ 0.05) em todas as propriedades físico-químicas avaliadas. O processo de liofilização e obtenção do concentrado proteico se mostraram eficientes alternativas para o uso dos resíduos do pirarucu no desenvolvimento de novos produtos, uma vez que diminuíram o teor de umidade (80,15% para 4,57%), como concentrou os minerais (1,60% para 7,55%) e proteínas (5,46% para 83,05%) e reduziu o teor lipídico (20,97% para 6,87%).

Effect of enzymatic complex in the diet of pirarucu, Arapaima gigas juveniles

ABSTRACT The pirarucu, Arapaima gigas is a native, carnivorous fish species from the Amazon basin. As carnivorous fish have low amylase activity, exogenous enzymes can improve the digestibility of carbohydrates in aquaculture feeds. We evaluated the digestibility of increasing levels of an enzymatic complex in diets of pirarucu juveniles (65.2 ± 0.4 g). The experimental design was randomized with four treatments [diets containing 0.25, 0.50, 0.75, and 1 g kg-1 on-top inclusion of an enzyme complex (Allzyme® SSF®, USA), and a control, with three replications at a density of 5 fish per unit, and a 30-day duration. We quantified apparent digestibility of dry matter, crude protein, and crude energy through nutrient and chromium oxide content in diets and feces. Enzymatic activity, hepatic glycogen and total protein were determined in liver and anterior intestine samples. The diet with 1 g kg-1 of enzyme-complex resulted in an increase in apparent digestibility of crude protein, gross energy, and dry matter, hepatic glycogen, total proteins in liver and in intestine, showing the efficiency of the enzyme complex in pirarucu feeding. A higher accumulation of dry matter, crude energy, and ethereal extract in the carcass indicated weight increase in the fish treated with enzymatic complex. A decrease in the endogenous enzymatic activity (protease, lipase and amylase) suggested an improved efficacy of the digestive process. Our results indicate that the inclusion of 1 g kg-1 enzyme complex in the diet of juvenile pirarucu can be recommended to achieve greater digestibility of nutrients and improvement in productive performance.

Novel Microsatellite Markers Used for Determining Genetic Diversity and Tracing of Wild and Farmed Populations of the Amazonian Giant Fish Arapaima gigas

The Amazonian symbol fish Arapaima gigas is the only living representative of the Arapamidae family. Environmental pressures and illegal fishing threaten the species’ survival. To protect wild populations, a national regulation must be developed for the management of A. gigas throughout the Amazon basin. Moreover, the reproductive genetic management and recruitment of additional founders by aquaculture farms are needed to mitigate the damage caused by domestication. To contribute to the sustainable development, we investigated the genetic diversity of wild and cultivated populations of A. gigas and developed a panel composed by 12 microsatellite markers for individual and population genetic tracing. We analyzed 368 samples from three wild and four farmed populations. The results revealed low rates of genetic diversity in all populations, loss of genetic diversity and high inbreeding rates in farmed populations, and genetic structuring among wild and farmed populations. Genetic tracing using the 12 microsatellite markers was effective, and presented a better performance in identifying samples at the population level. The 12-microsatellite panel is appliable to the legal aspects of the trade of the A. gigas, such as origin discrimination, reproductive genetic management by DNA profiling, and evaluation and monitoring of genetic diversity.